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  • 101.
    Engström, V.
    et al.
    Luleå tekniska universitet.
    Mihailova, Boriana
    Bulgarian Academy of Sciences.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Holmgren, Allan
    Sterte, Johan
    The effect of seed size on the growth of silicalite-1 films on gold surfaces2000In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 38, no 1, p. 51-60Article in journal (Refereed)
    Abstract [en]

    Silicalite-1 films grown on gold surfaces seeded with colloidal crystals with a size of 60, 165 and 320 nm were investigated by reflection–absorption infrared spectroscopy, scanning electron microscopy and X-ray diffraction in order to follow up the formation of nano-scale defects and to determine the optimal synthesis conditions for preparation of silicalite-1 films with a low concentration of defects. Using 60-nm-sized colloidal crystals, the seeding method was capable of producing silicalite-1 films with low concentrations of defects and with thicknesses ranging from 100 to 300 nm, which are predominantly oriented with the a-axis perpendicular to the surface. Hydrothermal treatment times of the 60-nm-seeded surfaces longer than 36 h as well as the seeding with 165 or 320 nm colloidal crystals substantially enhanced the formation of defects in the films.

  • 102.
    Erik, Sjölund
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Coating of blast furnace pellets2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 103.
    Escamilla-Roa, Elizabeth
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Cartwright, Julyan H. E.
    Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Armilla Granada, Spain. Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, Granada, Spain.
    Sainz-Díaz, C. Ignacio
    Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Armilla Granada, Spain.
    Chemobrionic Fabrication of Hierarchical Self‐Assembling Nanostructures of Copper Oxide and Hydroxide2019In: ChemSystemsChem, E-ISSN 2570-4206Article in journal (Refereed)
    Abstract [en]

    Copper oxide nanostructures have great potential use in a plethora of nanotechnology applications including nanoelectronics, photovoltaics, sensors, electrochemistry, and pharmacology. In the present work we show how hierarchically nano‐structured copper oxide and hydroxide may be prepared through self‐assembly from CuSO4 salt and silicate solutions using the chemobrionic growth process of a chemical garden. Procedures were explored using the cupric salt in either solid (pellet and seed growth methods) or liquid phase (fluid injection techniques). Self‐assembling nanostructures were characterized by means of environmental scanning electron microscopy (ESEM) with energy‐dispersive X‐ray spectroscopy (EDX) analysis, micro‐Raman spectroscopy and X‐ray diffraction. Our results show the formation of crystalline aggregates of copper oxide and hydroxide in complex hierarchical nanostructured forms including fans, flowers, petals, skeins, lentils, and sheaves. Analytical methods corroborate that these nanostructures may be selected in shape and chemical composition with the reaction conditions.

  • 104.
    Escamilla-Roa, Elizabeth
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Zorzano, María-Paz
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Centro de Astrobiología (INTA-CSIC), Torrejón de Ardoz, Madrid, Spain.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Granada, Spain.
    Hernäandez-Laguna, Alfonso
    Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Granada, Spain.
    Sainz-Diaz, Claro
    Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Granada, Spain.
    DFT study of electronic and redox properties of TiO2 supported on olivine for modelling regolith on Moon and Mars conditions2020In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 180, article id 104760Article in journal (Refereed)
    Abstract [en]

    Titanium dioxide TiO2 is one of the most studied oxides in photocatalysis, due to its electronic structure and its wide variety of applications, such as gas sensors and biomaterials, and especially in methane-reforming catalysis. Titanium dioxide and olivine have been detected both on Mars and our Moon. It has been postulated that on Mars photocatalytic processes may be relevant for atmospheric methane fluctuation, radicals and perchlorate productions etc. However, to date no investigation has been devoted to modelling the properties of TiO2 adsorbed on olivine surface.

    The goal of this study is to investigate at atomic level with electronic structure calculations based on the Density Functional Theory (DFT), the atomic interactions that take place during the adsorption processes for formation of a TiO regolith. This model is formed with different TiO films adsorbed on olivine (forsterite) surfaces, one of the most common minerals in Universe, Earth, Mars, cometary and interstellar dust. We propose three regolith models to simulate the principal phase of titanium oxide (TiO, Ti2O3 and TiO2). The models show different adsorption processes i.e. physisorption and chemisorption. Our results suggest that the TiO is the most reactive phase and produces a strong exothermic effect. Besides, we have detailed, from a theoretical point of view, the effect that has the adsorption process in the electronic properties such as electronic density of state (DOS) and oxide reduction process (redox). This theoretical study can be important to understand the formation of new materials (supports) that can be used as support in the catalytic processes that occur in the Earth, Mars and Moon. Also, it may be important to interpret the present day photochemistry and interaction of regolith and airborne aerosols in the atmosphere on Mars or to define possible catalytic reactions of the volatiles captured on the Moon regolith.

  • 105.
    Escamilla-Roa, Elizabeth
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Granada, Spain.
    Zorzano Mier, María-Paz
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Centro de Astrobiología (INTA-CSIC), Torrejón de Ardoz, Madrid, Spain.
    Martin-Torres, Javier
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Granada, Spain.
    Hernández-Laguna, Alfonso
    Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Granada, Spain.
    Saínz-Díaz, C.Ignacio
    Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Granada, Spain.
    DFT study of the reduction reaction of calcium perchlorate on olivine surface: Implications to formation of Martian’s regolith2020In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 512, article id 145634Article in journal (Refereed)
    Abstract [en]

    Perchlorates have been found widespread on the surface of Mars, their origin and degradation pathways are not understood to date yet. We investigate here, from a theoretical point of view, the potential redox processes that take place in the interaction of Martian minerals such as olivine, with anhydrous and hydrated perchlorates. For this theoretical study, we take as mineral substrate the (1 0 0) surface of forsterite and calcium perchlorate salt as adsorbate. Our DFT calculations suggests a reduction pathway to chlorate and chlorite. When the perchlorate has more than 4 water molecules, this mechanism, which does not require high-temperature or high energy sources, results in parallel with the oxidation of the mineral surface, forming magnesium peroxide, MgO2, and in the formation of ClO3, which through photolysis is known to form ClO-O2. Because of the high UV irradiance that reaches the surface of Mars, this may be a source of O2 on Mars. Our results suggest that this process may be a natural removal pathway for perchlorates from the Martian regolith, which in the presence of atmospheric water for salt hydration, can furthermore lead to the production of oxygen. This mechanism may thus have implications on the present and future habitability of the Martian surface.

  • 106.
    Fakhardji, Wissam
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Szabo, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    El-Kader, M.S.A.
    Department of Engineering Mathematics and Physics, Faculty of Engineering, Cairo University, Giza, Egypt. Department of Physics, Faculty of Sciences and Humanity Studies, Huraimla, Shaqra University, Shaqra, Saudi Arabia.
    Haskopoulos, Anastasios
    Department of Chemistry, University of Patras, Patras, Greece.
    Maroulis, George
    Department of Chemistry, University of Patras, Patras, Greece.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Collision-induced absorption in Ar–Kr gas mixtures: A molecular dynamics study with new potential and dipole data2019In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 151, no 14, article id 144303Article in journal (Refereed)
    Abstract [en]

    We have implemented a scheme for classical molecular dynamics simulations of collision-induced absorption. The program has been applied to a gas mixture of argon (Ar) and krypton (Kr). The simulations are compared with accurate quantum dynamical calculations. The comparisons of the absorption coefficients show that classical molecular dynamics is correct within 10% for photon wave numbers up to 220 cm−1 at a temperature of 200 K for this system. At higher temperatures, the agreement is even better. Molecular dynamics accounts for many-body interactions, which, for example, give rise to continuous dimer formation and destruction in the gas. In this way, the method has an advantage compared with bimolecular classical (trajectory) treatments. The calculations are carried out with a new empirical Ar–Kr pair potential. This has been obtained through extensive analysis of experimental thermophysical and transport properties. We also present a new high level ab initio Ar–Kr potential curve for comparison, as well as ab initio interaction-induced dipole curves computed with different methods. In addition, the Ar–Kr polarizability and hyperpolarizability are reported. A comparison of the computed absorption spectra with an experiment taken at 300 K shows satisfactory agreement although a difference in absolute magnitude of 10%–15% persists. This discrepancy we attribute mainly to experimental uncertainty.

  • 107.
    Falk, Joel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Effect of fuel composition and combustion conditions on phosphorus behavior during combustion of biomass2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Due to concerns for climate change and future supply of phosphorus fertilizer within agriculture, there has been an increased interest in the combustion of phosphorus containing waste residues and opportunity biomass fuels. Previous research has shown that during combustion, phosphorus has large impact on ash transformation reactions and may decrease or increase ash-related problems such as slag formation and bed agglomeration. This is a serious concern if new types of biomass are to be added for heat and power production. Additionally, plant studies and leaching tests of P-rich biomass ash indicate that the plant availability of phosphorus varies greatly with its association in the ash. As such, the ash transformation behavior of phosphorus is of great importance for the success of such ventures. While several studies have been made on the behavior of phosphorus during combustion, no comprehensive study has been made evaluating the effect of fuel composition and combustion conditions.

    In this work, the behavior of phosphorus was determined for a wide range of fuels and combustion conditions. More specifically, the objective was to determine (i) the effect of fuel ash composition and combustion technologies on the fate of phosphorus during combustion, (ii) investigate potential difference in the behavior of phosphorus during combustion of sewage sludge and plant based biomassand (iii)the effect of phosphorus on slag formation and bed agglomeration for the co-combustion of a wide range of plant based biomasses.

    The investigation was carried out by comparing experimental data gathered from the combustion of 26different biomass fuelsor fuel blends in a bench scale bubbling fluidized bed (5 kW, 18 experiments), an underfed pellet burner (20kW, 10 experiments) and a swirling powder burner (150 kW, 7 experiments). This included chemical characterization of bed ash, bottom ash and fly ash fractions by X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) in addition to qualitative measures of slagging-and bed agglomeration tendencies.

    It was found that phosphorus, irrespective of combustion technology and fuel composition, was mainly found in bed-, and bottom ash fractions and/or coarse fly ash fractions (>1μm). Based on the crystalline phase composition of the phosphates found in bed-, bottom-and coarse fly ash samples, phosphate speciation was correlated to the molar ratio between P, Ca and Mg for all three combustion technologies. Based on these results, it would be possible to control the behavior of phosphorus during combustion and the plant availability of phosphates in biomassash by designing fuel blends based on their fuel ash composition.

    In fluidized bed combustion, it was found that for similar combustion conditions and fuel ash compositions (with respect to K, Ca and P), the speciation of phosphorus in coarse ash fractions was significantly different from experiments with plant based biomass compared to sewage sludge. Unlike ash from plant based biomass, the crystalline phase composition of ash from sewage sludge did not change with the relative concentration of K, Ca andP in the fuel. The results suggest that the reaction pathway of phosphorus during combustion of sewage sludge is different to plant based biomass due to difference in the association of phosphorus in the fuel.

    The effect of phosphorus on slag formation and bed agglomeration in biomass combustion was mainly related to the relative fuel ash concentration of K, Ca, Mg, Si and P. In fluidized bed combustion, P contributes to the formation of agglomerates through the melt induced mechanism, through complex interaction with K, Ca, Mg and Si. Similarly, in fixed bed combustion the composition of slag indicatedthatslag formation involves the formation of P and Si rich ash melt with a varying content of K, Ca and Mg. In both cases, the severity of problems was related to the melting behavior of the (CaO,MgO)-K2O-(SiO2,P2O5) multicomponent system.

    The full text will be freely available from 2020-06-01 00:00
  • 108.
    Fan, Pengpeng
    et al.
    Herbert Gleiter Institute of Nanoscience, Department of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, P. R. China.
    Qiu, Xiuhua
    Herbert Gleiter Institute of Nanoscience, Department of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, P. R. China.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Ji, Qingmin
    Herbert Gleiter Institute of Nanoscience, Department of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, P. R. China.
    An, Rong
    Herbert Gleiter Institute of Nanoscience, Department of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, P. R. China. Center for Nanotechnology (CeNTech), Institute of Physics, Westfälische Wilhelms-Universität Münster, Münster, Germany.
    The effect of nanoscale friction of mesoporous carbon supported ionic liquids on the mass transfer of CO2 adsorption2020In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Physical chemistry chemical physicsArticle in journal (Refereed)
    Abstract [en]

    Supported ionic liquids (ILs) are attractive alternatives for CO2 capture and the thickness of supported IL films plays a critical role in the CO2 mass transfer rate. However, the dependence of CO2 uptake on the IL film thickness differs as the system varies. In this work, atomic force microscopy (AFM) is employed to probe the ‘nanofriction coefficient’ to characterize the mobility of ILs at the solid interface, in which, the smaller the nanofriction coefficient, the faster are the ionic mobility and CO2 mass transfer. A monotonic and almost linear relationship for supported IL films is obtained between the resistance of CO2 mass transfer (1/k) and the nanofriction coefficient (μ), avoiding the controversy over the effect of supported IL film thickness on CO2 adsorption. The enhanced mass transfer of CO2 adsorption at IL-solid interfaces is observed at smaller resistance 1/k and friction coefficient μ. The low-friction driven local mobility (diffusion) of ILs at solid interfaces is enhanced, promoting the exchange mixing of the ILs adsorbing CO2 with the ‘blank-clean’ ions of the ILs, and thus accelerating the CO2 mass transfer. The proposed correlation links the nanoscale friction with the mass transfer of CO2 adsorption, providing a fresh view on the design of ultra-low frictional supported ILs for enhanced CO2 capture and separation processes.

  • 109.
    Felippov, A.
    et al.
    Umeå university.
    Sulejmanova, A.
    Kazan State University, Tatarstan.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Grobner, G.
    Umeå university.
    Diffusion and aggregation of Alzheimer's Aβ1-40 peptide in aqueous trifluoroethanol solutions as studied by pulsed field gradient NMR2005In: Applied Magnetic Resonance, ISSN 0937-9347, E-ISSN 1613-7507, Vol. 29, no 3, p. 439-449Article in journal (Refereed)
    Abstract [en]

    Pulsed field gradient nuclear magnetic resonance technique was applied to measure the self-diffusion coefficient of Aβ1-40 peptide in trifluoroethanol (TFE) and mixed solvent TFE-water (D2O) buffer (pD 7.8) at 293 K. The data were analyzed on the basis of the Stokes model and the hard-sphere approach was used to estimate self-diffusion coefficients. It was found that the extent of the Aβ1-40 aggregation in TFE solutions depends on the concentration of the peptide and the sample preparation protocol. After soft mixing, i.e., without any additional mechanical pretreatment of the peptide, the peptide is present in the monomeric form in TFE solutions. However, the additional water-bath sonication of the sample during the dissolution of Aβ1-40 in TFE enforces oligomerization of the peptide with the size of aggregates ranging from tetra- to hexamers. An increase of D2O in the mixed TFE-D2O solvent of up to 75% leads to the aggregation of the larger part of the peptide. However, the components of self-diffusion coefficients related to low-mass Aβ1-40 oligomers (dimers and trimers) were not observed in the diffusion decay curves. The most probable explanation is that dimers and trimers are not the principal intermediate species in the aggregation of Aβ1-40 peptide (23 refs.)

  • 110.
    Feng, X.
    et al.
    Stockholms Universitet.
    Edén, M.
    Stockholms Universitet.
    Brinkmann, A.
    Stockholms Universitet.
    Luthman, H.
    Eriksson, L.
    Gräslund, A.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Levitt, M.H.
    Direct determination of a peptide torsional angle Ψ by double-quantum solid-state NMR1997In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 119, p. 12006-12007Article in journal (Other academic)
  • 111.
    Filippov, A. V.
    et al.
    Kazan State University, Tatarstan.
    Suleimanova, A. V.
    Kazan State University, Tatarstan.
    Grobner, G.
    Umea University, Department of Chemistry.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Effect of freezing on amyloid peptide aggregation and self-diffusion in an aqueous solution2008In: Colloid Journal of the Russian Academy of Science, ISSN 1061-933X, E-ISSN 1608-3067, Vol. 70, no 4, p. 501-506Article in journal (Refereed)
    Abstract [en]

    Pulsed-field gradient 1H NMR is employed to investigate the self-diffusion of amyloid Aβ-peptide in an aqueous buffer solution (pH 7.44) with a protein concentration of 50 μmol at 20°C. The self-diffusion coefficient of the peptide in a freshly prepared solution corresponds to its monomeric form. The storage of the solution at 24°C causes part of the peptide molecules to form amyloid aggregates as soon as over 48 h. However, the 1H NMR echo signal typical of aggregated molecules is not observed because of their dense packing in the aggregates and a large mass of the latter. A freezing-fusion of the solution after the aggregation does not cause changes in the self-diffusion coefficients of the peptide. After a peptide solution free of amyloid aggregates is subjected to a freezing-fusion cycle, part of the peptide molecules also remains in the monomeric form in the solution, while another part forms amyloid aggregates, with a portion of the aggregated peptide molecules retaining a high rotational mobility with virtually absolute absence of a translational mobility. The results obtained are interpreted in terms of the formation of "porous aggregates" of amyloid fibrils, with "pores" having sizes comparable with those of peptide molecules, though, being larger than water molecules. Peptide molecules, which do not form fibrils, are captured in the pores. Temperature regime is shown to be of importance for the aggregation of amyloid peptides. In particular, freezing, which is traditionally considered to be a method for the prevention from or temporary interruption of aggregation, may itself lead to the formation of amorphous amyloid aggregates, which remain preserved in solutions after their unfreezing.

  • 112.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Self-Diffusion and Microstructure of Some Ionic Liquids in Bulk and in Confinement2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    An ionic liquid (IL) is a salt, which usually is in the liquid state at normal temperature and pressure. The properties of ILs can be adjusted for various processes and applications by choosing different combinations of ions. Similar to other salts, ILs contain only ions with positive (cations) and negative (anions) charges in equal proportions. However, to prevent solidification, ions in ionic liquids usually contain bulky organic chemical groups, which, apart from electrostatic interactions, promote other types of interactions between ions, such as: (i) van-der-Waals interactions; (ii) hydrogen bonding; (iii) - stacking, etc., depending on the particular chemical structure of the ions. All these interactions, in combination, may lead to formation of specific microstructures in ILs, which may vary with temperature caused by changing thermal rotational and translational energies of the ions. Ions in these microstructures may have preferential orientations relative to each other, maintain anisotropic properties similar to those in liquid crystals or, in some specific cases, may even separate into microscopically organised liquid phases. Therefore, the dynamics of ILs may also be dependent on their microstructure. In many practical applications ionic liquids are placed on surfaces or in confinements. Solid surfaces introduce extra forces, which may be specific to the charge of the ions or/and to functional groups in the ILs. The geometry and interactions of ions in confinements or/and pores of materials may also disrupt specific bulk microstructures of ILs. Both confinement effects and interactions of ions with surfaces are manifested in the translational dynamics of the ions. One of the most direct and informative methods to study translational dynamics of ILs is pulse-field-gradient nuclear magnetic resonance (PFG-NMR).In this thesis the results of PFG-NMR studies on a few classes of ILs are reported: (i) the historically “standard” (since Walden’s discovery in 1914) ionic liquid, the ethylammonium nitrate (EAN) and (ii) halogen-free orthoborate-based phosphonium, imidazolium and pyrrolidinium ILs with varied structure and lengths of alkyl chains in cations, and varied structures of orthoborate anions. These ILs were studied in bulk at different temperatures, and also in confinements, such as between parallel glass and Teflon plates and in mesoporous Vycor glass. It was found that diffusion coefficients of cations and anions in EAN, phosphonium and pyrrolidinium orthoborate ILs in bulk are different, but according to the standard Stocks-Einstein model, they correspond to diffusion of ions in homogeneous liquids. A change in the chemical structure of one of the ions results in a change in both the diffusion coefficient of the oppositely charged ion and the activation energy of diffusion for both ions in an IL. Similar effects were observed from the chemical shifts and diffusion coefficients measured by NMR for imidazolium orthoborate ILs dissolved in polyethylene glycol solutions, in which imidazolium cations strongly interact with PEG molecules, further affecting the diffusion of orthoborate anions via electrostatic interactions. A liquid-liquid phase separation was suggested for a few phosphonium and pyrrolidinium bis(mandelato)borate ILs, in which a divergence of diffusion coefficients and activation energies of diffusion for cations and anions was detected at temperatures below ca 50 °C. In addition, a free-volume theory was invoked to explain the dependences of density of ILs on the alkyl chain length in cations.It was also found that for a phosphonium bis(salicylato)borate IL confined in 4 nm mesoporous Vycor glass the diffusion coefficients of ions increase by a factor of 35! This phenomenon was explained by the dynamic heterogeneity of this IL in micropores and empty voids of the Vycor glass. For EAN IL in confinements between glass and Teflon plates, the diffusion of ethylammonium cations and nitrate anions is significantly anisotropic, i.e. slower in the direction of the normal to the plates and faster along the plates compared to diffusion of the ions in bulk. A plausible explanation of this PFG NMR data is that EAN forms layers near polar and non-polar solid surfaces. A similar phenomenon, to a lesser extent, was also observed for phosphonium cations of bis(mandelato)borate, bis(salicylato)borate and bis(oxalato)borate confined between glass plates. The results of these studies may have implications in modeling tribological performance, i.e., friction and wear reduction for contact pairs of different materials lubricated by various classes of ionic liquids.

  • 113.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Synthesis and aggregation studies on amyloid oligomers of Alzheimer's Ab peptides2010Licentiate thesis, comprehensive summary (Other academic)
  • 114.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Influence of Alzheimer´s beta-amyloid peptide on the lateral diffusion of lipids in raft-forming bilayers2013In: Mendeleev communications (Print), ISSN 0959-9436, E-ISSN 1364-551X, Vol. 23, no 6, p. 316-318Article in journal (Refereed)
    Abstract [en]

    For the first time effect of added Alzheimer´s Abeta(1-40) peptide of wild type on lateral diffusion of lipids in macroscopically oriented bilayers of “raft” compositions (mixture of dioleoylphosphatidylcholine (DOPC), sphingomielin (SM) and cholesterol (CHOL)) was studied by NMR-diffusion technique. In homogeneous bilayers diffusion coefficients decrease, while in liquid ordered and in liquid disordered phases they change differently at varied concentrations of CHOL that was explained by decreased maximum solubility of CHOL in phospholipids in the presence of Abeta(1-40) peptide.

  • 115.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Institute of Physics, Kazan Federal University, Kazan, Russia .
    Antzutkin, Oleg N.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Department of Physics, Warwick University, Coventry, United Kingdom .
    Magnetic field effects dynamics of ethylammonium nitrate ionic liquid confined between glass plates2018In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 9, p. 6316-6320Article in journal (Refereed)
    Abstract [en]

    Self-diffusion and NMR relaxation of the ethylammonium (EA) cation were studied in the protic ionic liquid, ethylammonium nitrate (EAN), confined between polar glass plates separated by a few μm distance and exposed to an external magnetic field of 9.4 T. The diffusion coefficient of EA (D) and the transverse NMR relaxation rate (1/T2) of –NH3 protons were increased immediately after placing the sample in the magnetic field by factors of ∼2 and ∼22, respectively, in comparison with those of bulk EAN. Further exposure of the sample to the magnetic field led to gradual changes in D, T1 and T2 towards their bulk values with a time constant of ∼70 min. Complete “recovery” of the sample to the “accelerated” D and “shortened” T2 values occurred at longer than 24 hours after the removal of the EAN sample from the magnet. Because the observed characteristic times of the change far exceed the times of molecular processes in EAN, we suggested that this phenomenon is related to reversible phase transformations occurring in confined EAN.

  • 116.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Kazan State Medical University, Kazan, Russia.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Department of Physics, Warwick University, Coventry, UK.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rapid carbene formation increasing ion diffusivity in an imidazolium acetate ionic liquid confined between polar glass plates2019In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, no 40, p. 22531-22538Article in journal (Refereed)
    Abstract [en]

    1-Ethyl-3-methyl-imidazolium acetate ([EMIM][OAc]) is one of the most widely used ionic liquids for various applications. This study is focussed on the chemical stability of [EMIM][OAc] on the surfaces of polar glass plates. 1H and 13C NMR spectroscopy and NMR diffusometry of [EMIM][OAc] IL confined between glass plates with a specific surface area 105–106 m−1 are thoroughly investigated. A rapid and spontaneous reaction took place on the surfaces of glass plates leading to the formation of neutral chemical moieties as evident by the appearance of new signals in the 1H NMR spectra. These new products are assigned as N-heterocyclic carbene (NHC) and acetic acid. These neutral chemical moieties have significantly increased the ion diffusivity by dissociation of the cation and the anion in [EMIM][OAc] IL. The yield and rate of formation of NHC and acetic acid are found to increase with the increasing surface area of polar glass plates and the time of contact between the IL and glass surfaces. Based on NMR spectroscopy, a dissociative reaction mechanism is proposed for the formation of free NHC in the neat [EMIM][OAc] IL.

  • 117.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Kazan State Medical University, Kazan, Russia.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Department of Physics, Warwick University, Coventry, UK.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Reactivity of CO2 with aqueous choline-based ionic liquids probed by solid-state NMR spectroscopy2019In: Journal of Molecular Liquids, ISSN 0167-7322, E-ISSN 1873-3166, Vol. 286, article id 110918Article in journal (Refereed)
    Abstract [en]

    CO2 absorption in a series of choline-based ionic liquids is investigated using solid-state 13C and 15N MAS NMR spectroscopy. Natural abundance and 13C enriched CO2 gas was purged through 50 wt% aqueous solutions of alkyldimethyl(2-hydroxyethyl)ammonium threonine, [N1,1,n,2OH][Threo], (alkyl = butyl, pentyl and hexyl) and pentyldimethyl(2-hydroxyethyl)ammonium taurine [N1,1,5,2OH][Tau]. The process of CO2 absorption results in precipitation of a solid sediment, which stays in equilibrium with the liquid phase. Upon degassing of the sample, the sediment is dissolved back into the IL-aqueous phase. Solid state 13C and 15N MAS NMR data suggest that the solid sediment is composed of neutral threonine (or taurine) in the zwitterionic forms and the liquid phase contained the products of reactions between the ionic liquids and CO2 molecules. A plausible mechanism for formation of the solid sediments and the reaction products in liquid phases is suggested.

  • 118.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Department of Physics, Warwick University, Coventry, U.K.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Understanding the Interaction of Boric Acid and CO2 with Ionic Liquids in Aqueous Medium by Multinuclear NMR Spectroscopy2020In: ACS Sustainable Chemistry & Engineering, Vol. 8, p. 552-560Article in journal (Refereed)
    Abstract [en]

    Boric acid is known to enhance the kinetics of CO2 absorption by some active aqueous solutions. However, the mechanism of interaction of boric acid with the CO2 in the presence of active molecules is not yet fully understood. In this work, interaction and dynamics of ions in aqueous solutions of functionalized choline-based ionic liquids [N1,1,5,2OH][Threo] and [N1,1,5,2OH][Tau] in the presence of boric acid and CO2 is thoroughly investigated using multinuclear NMR approach: 13C and 11B NMR spectroscopy, 11B NMR transverse relaxation as well as 1H and 11B NMR diffusometry. 13C and 11B NMR spectroscopy has revealed the formation of borate based complexes as a result of reaction between boric acid and anions of the ILs at ionic liquid/boric acid molar ratios larger than ca. 0.15. The formation of these complexes and their dynamics are further investigated using 11B relaxation, and 1H and 11B pulse-field-gradient (PFG) NMR. A plausible reaction mechanisms of boric acid with the anions of the IL, formation of the borate complexes and dissociation of these complexes facilitated by CO2 molecules are suggested.

  • 119.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Artamonova, Marina
    Kazan (Volga Region) Federal University, Kazan.
    Rudakova, Maya
    Kazan (Volga Region) Federal University, Kazan.
    Gimatdinov, Roustam
    Kazan (Volga Region) Federal University, Kazan.
    Skirda, Vladimir
    Kazan (Volga Region) Federal University, Kazan.
    Self-diffusion in a hyaluronic acid–albumin–water system as studied by NMR2012In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 50, no 2, p. 114-119Article in journal (Refereed)
    Abstract [en]

    In the presence of even a small amount of hyaluronic acid, the self-diffusion coefficient of albumin decreases. Three hypotheses were proposed and analyzed. The most likely one is that BSA and HA molecules form complex. The state of the BSA molecules in the BSA-HA-D2O system corresponds to a ‘fast exchange’ condition from the NMR point of view: BSA molecules reside in the ‘free’ and ‘bound’ states for much shorter time than the diffusion time of the PFG NMR experiment. Hyaluronic acid (HA) is an anionic biopolymer that is present in many tissues and can be involved in cancerous neoformations. HA can form complexes with proteins (particularly, serum albumin) in the body. However, HA structures and processes involving HA have not been extensively studied by NMR because the molecule's rigid structure makes these studies problematic. In the current work, self-diffusion of HA and bovine serum albumin (BSA), and water in solutions was measured by 1H pulsed field gradient NMR (PFG NMR) with a focus on the HA-BSA-D2O systems at various concentrations of BSA and HA. It was shown that in the presence of even a small amount of HA, the self-diffusion coefficient (SDC) of BSA decreases. To explain this fact, three hypotheses were proposed and analyzed. The first one was based on the effect of slowing down of water mobility in the presence of HA. The second hypothesis suggested an effect of mechanical collisions of BSA with HA molecules. The third hypothesized that BSA and HA molecules form a complex where BSA molecules reduced in mobility. It was shown that the third mechanism is the most likely. The state of the BSA molecules in the BSA-HA-D2O system corresponds to a ‘fast exchange’ condition from the NMR point of view: BSA molecules reside in the ‘free’ and ‘bound’ (with HA) states for much shorter time than the diffusion time of the PFG NMR experiment, 7 ms. The fractions of ‘bound’ BSA molecules in the BSA-HA complex were estimated.

  • 120.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Azancheev, Nail
    Institute of Physics, Kazan Federal University, Kazan, Russia.
    Gibaydullin, Amal
    Institute of Physics, Kazan Federal University, Kazan, Russia.
    Bhattacharyya, Shubhankar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Antzutkin, Oleg N.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Dynamic Properties of Imidazolium Orthoborate Ionic Liquids Mixed with Polyethylene Glycol Studied by NMR Diffusometry and Impedance Spectroscopy2018In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 56, no 2, p. 113-119Article in journal (Refereed)
    Abstract [en]

    We used 1H pulsed field gradient (PFG) NMR to study the self-diffusion of polyethylene glycol (PEG) with average molecular mass of 200 and ions in mixtures of PEG with imidazolium bis(mandelato)borate (BMB) and imidazolium bis(oxalato)borate (BOB) ionic liquids (ILs). The ionic liquid was mixed with PEG in the concentration range of 0–100 wt%. Within the temperature range of 295 to 353 K, the diffusion coefficient of BMB is slower than that of the imidazolium cation. The diffusion coefficients of PEG, as well as the imidazolium cation and BMB anions, differ under all experimental conditions tested. This demonstrates that the IL in the mixture is present in at least a partially dissociated state. Generally, increasing the concentration of PEG leads to an increase in the diffusion coefficients of PEG and both the ions, and decreases their activation energy for diffusion. NMR chemical shift alteration analysis showed that the presence of PEG changes the chemical shifts of both ions but in different directions. Impedance spectroscopy was used to measure the ionic conductivity of the ionic liquids mixed with PEG.

  • 121.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Azancheev, Nail
    Kazan (Volga Region) Federal University, Kazan.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Glavatskikh, Sergei
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Self-Diffusion of Phosphonium Bis(Salicylato)Borate Ionic Liquid in Pores of Vycor Porous Glass2016In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 230, p. 128-134Article in journal (Refereed)
    Abstract [en]

    1H NMR pulsed field gradient was used to study self-diffusion of a phosphonium bis(salicylato)borate ionic liquid ([P6,6,6,14][BScB]) in the pores of Vycor porous glass at 296 K. Confinement in pores increases diffusion coefficients of the ions by a factor of 35. However, some [P6,6,6,14][BScB] ions demonstrated apparent diffusion coefficients much lower than their mean values, which may be due to partially restricted diffusion of the ions. We suggest that this fraction corresponds to areas where ions are confined by pore ‘necks’ (micropores) and empty voids. Heating of the ionic liquid / Vycor system at 330 K led to a change in the diffusivity of the ions, because of their redistribution in the pores. The size of the bounded regions is on the order of 1 µm, as estimated from the dependence of the ion diffusivity on the diffusion time.

  • 122.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Azancheev, Nail
    Kazan (Volga Region) Federal University, Kazan.
    Taher, Mamoun
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rabét, Pauline
    Department of Organic Chemistry, School of Chemistry, Manchester University.
    Glavatskih, Sergei
    System and Component Design, KTH, Royal Institute of Technology , Machine Design, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden, Department of Physics, Warwick University, Coventry, Department of Mechanical Construction and Production, Ghent University.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Self-diffusion and interactions in mixtures of imidazolium bis(mandelato)borate ionic liquids with polyethylene glycol: 1H NMR study2015In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 53, no 7, p. 493-497Article in journal (Refereed)
    Abstract [en]

    We used 1H nuclear magnetic resonance pulsed-field gradient to study the self-diffusion of polyethylene glycol (PEG) and ions in a mixture of PEG and imidazolium bis(mandelato)borate ionic liquids (ILs) at IL concentrations from 0 to 10 wt% and temperatures from 295 to 370 K. PEG behaves as a solvent for these ILs, allowing observation of separate lines in 1H NMR spectra assigned to the cation and anion as well as to PEG. The diffusion coefficients of PEG, as well as the imidazolium cation and bis(mandelato)borate (BMB) anion, differ under all experimental conditions tested. This demonstrates that the IL in the mixture is present in at least a partially dissociated state, while the lifetimes of the associated states of the ions and ions with PEG are less than ~30 ms. Generally, increasing the concentration of the IL leads to a decrease in the diffusion coefficients of PEG and both ions. The diffusion coefficient of the anion is less than that of the cation; the molecular mass dependence of diffusion of ions can be described by the Stokes–Einstein model. NMR chemical shift alteration analysis showed that the presence of PEG changes mainly the chemical shifts of protons belonging to imidazole ring of the cation, while chemical shifts of protons of anions and PEG remain unchanged. This demonstrated that the imidazolium cation interacts mainly with PEG, which most probably occurs through the oxygen of PEG and the imidazole ring. The BMB anion does not strongly interact with PEG, but it may be indirectly affected by PEG through interaction with the cation, which directly interacts with PEG

  • 123.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Institute of Physics, Kazan Federal University, Russia.
    Bhattacharyya, Shubhankar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    CO2 absorption and ion mobility in aqueous choline-based ionic liquids2019In: Journal of Molecular Liquids, ISSN 0167-7322, E-ISSN 1873-3166, Vol. 276, p. 748-752Article in journal (Refereed)
    Abstract [en]

    CO2 absorption and ion mobility are investigated in a series of 50/50 wt% aqueous solutions of choline-based ionic liquids with different cations and anions: [N1,1,4,2OH][Threo], [N1,1,5,2OH][Threo], [N1,1,6,2OH][Threo], [N1,1,5,2OH][β-ala] and [N1,1,5,2OH][Tau]. The process of CO2 absorption was completed in an hour reaching maximum of absorption capacity 0.07–0.10 wt% to ionic liquid (by 0.4–0.6 molar ratios). A rapid CO2 absorption is observed by the formation of solid product as a result of reaction between CO2 molecule and the ionic liquid. Diffusion coefficients of the cation and anion in the mixture are comparable while the diffusivity of water molecules is found to be quite different from the ions. In the process of CO2 absorption, an increase in the diffusivity of ions is observed due to the precipitation of solid products and depletion of ions contents in the liquid phase of the system. 13C NMR measurements of diffusivity of CO2 enriched with 13C isotope showed that a part of the absorbed CO2 remained in the liquid phase being physically and chemically bound to ions. The ionic liquid is re-cycled by evaporating water and releasing CO2 molecules using vacuum and temperature.

  • 124.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Institute of Physics, Kazan Federal University.
    Gnezdilov, Oleg I.
    Institute of Physics, Kazan Federal University.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Department of Physics, Warwick University, Coventry.
    Static magnetic field alters properties of confined alkylammonium nitrate ionic liquids2018In: Journal of Molecular Liquids, ISSN 0167-7322, E-ISSN 1873-3166, Vol. 268, p. 49-54Article in journal (Refereed)
    Abstract [en]

    Ethylammonium nitrate (EAN) and propylammonium nitrate (PAN) ionic liquids confined between polar glass plates and exposed to a strong magnetic field of 9.4 T demonstrate gradually slowing diffusivity, a process that can be reversed by removing the sample from the magnetic field. The process can be described well by the Avrami equation, which is typical for autocatalytic (particularly, nucleation controlled) processes. The transition can be stopped by freezing the sample. Cooling and heating investigations showed differences in the freezing and melting behavior of the sample depending on whether it had been exposed to the magnetic field. After exposure to the magnetic field, the sample demonstrated decrease in the 1H NMR signal of residual water. 1H NMR spectroscopy with presaturation demonstrates that the most probable mechanism of the decrease of the bulk water signal is adsorption of water on polar surfaces of glass plates. Generally, our findings confirm our previous suggestion that alteration of the dynamic properties of confined alkylammonium nitrate ionic liquids exposed to a magnetic field is related to the alteration of real physical-chemical phases

  • 125.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Gnezdilov, Oleg I.
    Institute of Physics, Kazan Federal University.
    Hjalmarsson, Nicklas
    Surface and Corrosion Science, KTH Royal Institute of Technology.
    Antzutkin, Oleg N.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Glavatskih, Sergei
    System and Component Design, Department of Machine Design, KTH Royal Institute of Technology.
    Furo, Istvan
    Applied Physical Chemistry, KTH Royal Institute of Technology.
    Rutland, Mark W.
    Surface and Corrosion Science, KTH Royal Institute of Technology.
    Acceleration of diffusion in ethylammonium nitrate ionic liquid confined between parallel glass plates2017In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 38, p. 25853-25858Article in journal (Refereed)
    Abstract [en]

    Diffusion of EAN confined between polar glass plates separated by a few micrometers is higher by a factor of ca. 2 as compared to bulk values. Formation of a new phase, different to the bulk, was suggested.

  • 126.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Kazan State Medical University, Kazan, Russia.
    Gnezdilov, Oleg I.
    Kazan Federal University, Kazan, Russia. Zavoisky Physical-Technical Institute, FRC Kazan Scientific Center, Russian Academy of Sciences, Kazan, Russia.
    Luchkin, Alexander G.
    Kazan Federal University, Kazan, Russia.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Self-diffusion of ethylammonium nitrate ionic liquid confined between modified polar glasses2019In: Journal of Molecular Liquids, ISSN 0167-7322, E-ISSN 1873-3166, Vol. 284, p. 366-371Article in journal (Refereed)
    Abstract [en]

    Ethylammonium nitrate (EAN) ionic liquid confined between flat polar glass platesdemonstrates variable diffusivity that is sensitive to an external static magnetic field. Outside the magnetic field, diffusivity between the plates is higher than that in the bulk. However, after placing the system in a strong static magnetic field, the diffusivity gradually decreased. These processes occur during transformations between phases formed in EAN subjected to micrometer-size restrictions outside and within the magnetic field (Filippov et al., JMolLiq. [2018] 268, 49). In this study, we used samples of two types: (i) with roughened surface formed by treatment of the glass plates with aqueous solutions of hydrofluoric acid and (ii) with vacuum deposited TiO2 layers with a thickness of ca. 1 μm at glass-plate edges. Neither the surface modification of the glass plates, nor the TiO2 layers controlled thickness of EAN confined between glass-plates significantly changed the above-described effects, which have been observed in studies using untreated glass plates. Therefore, the range of systems with detected phase transformations in EAN and accompanying effects, such as accelerated diffusivity and change in diffusivity under the influence of a static magnetic field, was expanded to the systems with roughened surfaces and the systems with TiO2 layers controlled inter-plates distances. Results of experiments with roughened surfaces additionally suggested that the phase transformation of confined EAN in the external magnetic field is isotropic in nature rather than a phase transition from “layered to bulk” structures.

  • 127. Filippov, Andrei
    et al.
    Gröbner, G.
    Umeå university.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Alzheimer's Ab(1-40)-peptide aggregation in TFE caused by ultrasonication2009In: International Bunsen Discussion Meeting on "Structure of Amyloid Fibrils and Mechanism of Amyloid Formation", 8-11 February 2009, Halle an der Saale (Germany): Abstract Book, 2009, p. 15-Conference paper (Other academic)
    Abstract [en]

    The translational diffusion of Alzheimer's Aβ(1-40)-peptide in sonicated trifluoroethanol (TFE) solutions was studied by the 1H NMR-diffusomery technique. Sonication was performed at the ultrasound frequency of 50 kHz and with the output of 80 W. In freshly-prepared solutions (without any preaggregates of the peptide) diffusion of Aβ(1-40) can be described by an unique diffusion coefficient (~1×10-10 m2/s), which corresponds to the calculated diffusion coefficient of Aβ(1-40) monomers using the Stokes-Einstein hard-sphere approximation. For untreated samples both the diffusion coefficient and the NMR signal amplitude were not changing with time that suggests no aggregation of the peptide in TFE. In contrary, the diffusion decay of the stimulated spin-echo in sonicated samples was more complex suggesting a presence of a few components with different diffusion coefficients. The diffusion decay was separated into spectral components using the CORE method for global analysis of correlated spectral data. This analysis revealed a new diffusion component, which is characterized by a very small diffusion coefficient (<1×10-13 m2/s), which may be attributed to large oligomers of Aβ(1-40) formed upon sonication. A fraction of this component from the total integral intensity of the 1H NMR signal does depend on the sonication time but it does not change during NMR measurements and the following storage of the sample. In all samples a large fraction of the peptide adopts the a-helical secondary structure as revealed by circular dichroism measurements. Upon ultrasonication this secondary structure changes only insignificantly. Therefore, ultrasonication leads to aggregation of Aβ(1-40)-peptide in TFE, without a detectable (by CD) disruption of its a-helical secondary structure.  An increase in the integral intensity of the 1H NMR signal in sonicated samples of Aβ(1-40) in TFE may be interpreted in terms of the transverse relaxation times, T2, of the solvent and Aβ(1-40) monomers: these times do increase as the fraction of Aβ(1-40) aggregates increases in the sample upon sonication. This effect can be further explained by either a concentration dependence of T2 (that reflects a changing ratio of "free" and "bound" solvent to the peptide molecules) or/and by a conformational change in Aβ(1-40) monomers as a result of sonication. Additional spin-echo T2-relaxation time measurements and 1H 2D NOESY NMR may assist in understanding of these interesting effects in sonicated solutions of Aβ(1-40) in TFE. Putative aggregation mechanisms and structures of monomers and oligomers in Aβ(1‑40)/TFE solutions at different duration of sonication are also discussed.

  • 128. Filippov, Andrei
    et al.
    Gröbner, G.
    Umeå university.
    Klochkov, V.
    Kazan State University, Tatarstan.
    Julmetov, A.
    Kazan State University, Tatarstan.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Aggregation on an amyloid peptide as studied by NMR diffusometry and 2D NMR noesy spectroscopy2009In: Protein folds in infectious and neurodegenerative diseases, Centre National de la Recherche Scientifique, CNRS , 2009, p. 91-Conference paper (Other academic)
    Abstract [en]

    Alzheimer's disease is a progressive neurodegenerative disorder affecting millions of people world-wide. Alzheimer's amyloid-b peptide forms amorphous aggregates or amyloid fibrils. However, recent studies indicate that soluble oligomers instead of fibrils may form probably most neurotoxic species. These oligomeric aggregates are difficult to study by traditional structural experimental techniques. NMR diffusometry offer useful additional possibilities.  In freshly-prepared solutions (without any pre-aggregates of the peptide) diffusion of the peptide can often be described by an unique diffusion kinetics, which corresponds to the calculated diffusion coefficient of the amyloid- b peptide monomers with the Stokes-Einstein hard-sphere approximation (typically D ~10-10 m2/s). In a quasi-equilibrium or in pulse-induced conditions, new larger aggregates of Ab with diffusion coefficients down to <1×10-13 m2/s were detected. 2D 1H NMR NOESY provides both an additional evidence of aggregation and also reveals most probable sites of the side chain interactions in the aggregates. "Pulse-like" treatment of the sample involves: (i) changing of the solution composition; (ii) freezing-thawing; and (iii) sonication of the sample in the course of its incubation. Putative aggregation mechanisms and structures of monomers and oligomers in solutions at different conditions are discussed.1.   Filippov A., Sulejmanova A., Antzutkin O. and Gröbner G. (2005) Diffusion and aggregation of Alzheimer's Abeta(1-40)-peptide in aqueous-TFE solutions as studied by pulsed field gradient NMR. Applied Magnetic Resonance. 29. 439 - 449.2.   Filippov A., Sulejmanova A., Gröbner G. and Antzutkin O. (2008) Effect of freezing on amyloid peptide aggregation and self-diffusion in an aqueous solution. Colloid J. 70. 501-506.3.   Filippov A., Gröbner G. and Antzutkin O. Effect of ultrasonication on amyloid peptide aggregation in trifluoroethanol solution. (in preparation).

  • 129.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gröbner, Gerhard
    Biological Chemistry, Institute of Chemistry, Umeå University.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Aggregation of amyloid Aβ(1-40) peptide in perdeuterated 2,2,2-trifluoroethanol caused by ultrasound sonication2010In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 48, no 6, p. 427-434Article in journal (Refereed)
    Abstract [en]

    Ultrasound sonication of protein and peptide solutions is routinely used in biochemical, biophysical, pharmaceutical and medical sciences to facilitate and accelerate dissolution of macromolecules in both aqueous and organic solvents. However, the impact of ultrasound waves on folding/unfolding of treated proteins, in particular, on aggregation kinetics of amyloidogenic peptides and proteins is not understood. In this work, effects of ultrasound sonication on the misfolding and aggregation behavior of the Alzheimer's Aβ (1-40)-peptide is studied by pulsed-field gradient (PFG) spin-echo diffusion NMR and UV circular dichroism (CD) spectroscopy. Upon simple dissolution of Aβ(1-40) in perdeuterated trifluoroethanol, CF3-CD2-OD (TFE-d3), the peptide is present in the solution as a stable monomer adopting α-helical secondary structural motifs. The self-diffusion coefficient of Aβ(1 -40) monomers in TFE-d3 was measured as 1.35 × 10-10 m2 s-1, reflecting its monomeric character. However, upon ultrasonic sonication for less than 5 min, considerable populations of Aβ molecules (ca 40%) form large aggregates as reflected in diffusion coefficients smaller than 4.0 × 10-13 m2 s-1. Sonication for longer times (up to 40 min in total) effectively reduces the fraction of these aggregates in 1H PFG NMR spectra to ca 25%. Additionally, absorption below 230 nm increased significantly upon sonication treatment, an observation, which also clearly confirms the ongoing aggregation process of Aβ(1-40) in TFE-d3. Surprisingly, upon ultrasound sonication only small changes in the peptide secondary structure were detected by CD: the peptide molecules mainly adopt α-helical motifs in both monomers and aggregates formed upon sonication.

  • 130.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Khakimov, Aidar
    Kazan (Volga Region) Federal University, Kazan.
    Afonin, Sergii
    Karlsruhe Institute of Technology.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Interaction of prostatic acid phosphatase fragments with a lipid bilayer as studied by NMR spectroscopy2013In: Mendeleev communications (Print), ISSN 0959-9436, E-ISSN 1364-551X, Vol. 23, no 6, p. 313-315Article in journal (Refereed)
    Abstract [en]

    Effects of five fragments of prostatic acid phosphatase on the dimyiristoylphosphatidilcholine lipid multi-lamellar liposomes were studied by 2H and 31P NMR spectroscopy and on planar supported multi-bilayers of the same lipid by 1H and 31P NMR spectroscopy. It was found that hydrophobic interaction is dominated factor of the peptide–membrane binding, while short alpha-helical fragments PAP(262-270) and PAP(262-272) strongly interact to membrane at the interface, generally following to the Gibbs free energy of water-to-interface insertion.

  • 131.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Khakimov, Aidar
    Kazan (Volga Region) Federal University, Kazan.
    Munavirov, Bulat
    Kazan (Volga Region) Federal University, Kazan, Institute of Physics, Kazan (Volga Region) Federal University.
    31P NMR Studies of Phospholipids2015In: Annual Reports on NMR Spectroscopy, ISSN 0066-4103, E-ISSN 2163-6052, Vol. 85, p. 27-92Article in journal (Refereed)
    Abstract [en]

    31P nuclear magnetic resonance (NMR) can provide information on the composition of phospholipid (PL) membranes, lipid headgroup orientation relative to the bilayers normal, and the phase state of PL systems. Interaction of the membrane with ions, drugs, other small molecules and peptides may lead to lipid phase change and lamellar phase disturbances, which can also be revealed in 31P NMR spectra. Traditional 31P NMR spectroscopy has been used for years, mainly to study lipid phase state. In the last few years, however, its utility has been extended by a number of solid-state methods in field-cycling spectroscopy. Membrane mimicking systems have been complemented with bicelles, which are more convenient for studying peptide structure in lipid–peptide interactions. Another challenge is the study of ordered membrane domains (rafts) induced in the presence of cholesterol or certain proteins. As a result, recent work has refined the structure of PL headgroups and elucidated membrane responses to interactions with peptides and other molecules. Selected examples of such fascinating investigations are presented here.

  • 132.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Kotenkov, Sergey A.
    Kazan (Volga Region) Federal University, Kazan.
    Munavirov, Bulat
    Kazan (Volga Region) Federal University, Kazan.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Effect of Curcumin on Lateral Diffusion of Phosphatidylcholines in Saturated and Unsaturated Bilayers2014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 35, p. 10686-10690Article in journal (Refereed)
    Abstract [en]

    Curcumin, a dietary polyphenol, is a natural spice with preventive and therapeutic potential for neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Curcumin possesses a spectrum of antioxidant, anti-inflammatory, anticarcinogenic, and antimutagenic properties. Because of this broad spectrum of pharmacological activity, it has been suggested that, like cholesterol, curcumin exerts its effect on a rather basic biological level, such as on lipid bilayers of biomembranes. The effect of curcumin on translational mobility of lipids in biomembranes has not yet been studied. In this work, we used 1H NMR diffusometry to explore lateral diffusion in planar-oriented bilayers of dimyristoylphosphatidylcholine (DMPC) and dioleoylphosphatidylcholine (DOPC) at curcumin concentrations of up to 40 mol % and in the temperature range of 298-333 K. The presence of curcumin at much lower concentrations (∼7 mol %) leads to a decrease in the lateral diffusion coefficient of DOPC by a factor of 1.3 at lower temperatures and by a factor of 1.14 at higher temperatures. For DMPC, the diffusion coefficient decreases by a factor of 1.5 at lower temperatures and by a factor of 1.2 at higher temperatures. Further increasing the curcumin concentration has no effect. Comparison with cholesterol showed that curcumin and cholesterol influence lateral diffusion of lipids differently. The effect of curcumin is determined by its solubility in lipid bilayers, which is as low as 10 mol % that is much less than that of cholesteroĺs 66 mol %.

  • 133.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Kotenkov, Sergey A.
    Kazan (Volga Region) Federal University, Kazan, Institute of Physics, Kazan (Volga Region) Federal University.
    Munavirov, Bulat
    Kazan (Volga Region) Federal University, Kazan, Institute of Physics, Kazan (Volga Region) Federal University.
    Khaliulina, Aliya V.
    Institute of Physics, Kazan (Volga Region) Federal University.
    Gnezdilov, Oleg I.
    Kazan (Volga Region) Federal University, Kazan, Institute of Physics, Kazan (Volga Region) Federal University.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Effect of curcumin on lateral diffusion in lipid bilayers2016In: Mendeleev communications (Print), ISSN 0959-9436, E-ISSN 1364-551X, Vol. 26, no 2, p. 109-110Article in journal (Refereed)
    Abstract [en]

    Lateral diffusion in dimyristoylphosphatidylcholine lipid bilayers decreases in the presence of cholesterol and curcumin, as measured by 1H NMR spectroscopy, but the mechanisms of action of these two compounds are different.

  • 134.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Kazan State Medical University, Kazan, Russian Federation.
    Kurakin, S.
    Institute of Physics, Kazan Federal University, Kazan, Russian Federation.
    Gnezdilov, O.I.
    Institute of Physics, Kazan Federal University, Kazan, Russian Federation.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Department of Physics, Warwick University, Coventry, United Kingdom.
    Effect of magnetic field on diffusion of ethylammonium nitrate: water mixtures confined between polar glass plates2018In: Journal of Molecular Liquids, ISSN 0167-7322, E-ISSN 1873-3166, Vol. 4, p. 45-51Article in journal (Refereed)
    Abstract [en]

    We used 1H NMR diffusometry to study mixtures of ethylammonium nitrate (EAN) with water (3.1–12.4 mol% of added H2O) confined between polar glass plates and exposed to a static magnetic field of 9.4 T. The presence of such restrictions reverses the concentration dependence of the diffusivities of the EA (ethylammonium) cation and water typical for the bulk system. The presence of water weakens the effects of a static magnetic field on diffusion of the EA cation as well as on proton exchange of –NH3 groups. Surprisingly, the amplitude of the echo signal of water protons decreases during exposure to the magnetic field and finally disappears, a phenomenon that depends on the concentration of water in the system. Based on experimental data, we suggest that water in the system is present in two states with different dynamic properties. One type of water formed in confinement possesses NMR relaxation time typical for liquids; its diffusivity can be measured by 1H NMR. The second type of water is formed upon exposure of the sample of the first type to the magnetic field and eventually includes all the water in the system. This type of water possesses “solid-like” NMR relaxation features that makes it “invisible” to the NMR diffusometry technique. We suggest that this second type of water is adsorbed onto the glass plates. Correspondingly, EAN exists in two liquid phases: the first one contains an EAN-water mixture, while the second one contains neat EAN, and forms on the microscopic scale range under the influence of a static magnetic field.

  • 135.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Munavirov, Bulat
    Kazan (Volga Region) Federal University, Kazan.
    Gizatullin, Bulat
    Kazan (Volga Region) Federal University, Kazan.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Disordering of phospholipid headgroups induced by a small amount of polyethylene oxide2013In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 51, no 1, p. 1-3Article in journal (Refereed)
    Abstract [en]

    We present a 31P NMR spectroscopy study of planar glass-plate-oriented multi-bilayers of dimyristoylphosphatidylcholine (DMPC) with addition of polyethylene oxide (PEO). This work revealed the presence of a new component in the spectra that appeared only with addition of a small fraction of PEO (up to one PEO segment per dimyristoylphosphatidylcholine molecule) and disappeared when larger amounts of PEO were added. We explained this phenomenon as an effect of an inhomogeneous force field induced by the PEO molecules located at a certain depth in the lipid membrane interface region

  • 136.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Munavirov, Bulat
    Kazan (Volga Region) Federal University, Kazan.
    Sparrman, Tobias
    Umeå university.
    Ishmuhametova, Valentina
    Kazan (Volga Region) Federal University, Kazan.
    Rudakova, Maya
    Kazan (Volga Region) Federal University, Kazan.
    Shriram, Prashant
    Umeå university.
    Tavelin, Staffan
    Umeå university.
    Interaction of a Poly(acrylic acid) Oligomer with Dimyristoylphosphatidylcholine Bilayers2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 7, p. 3754-3761Article in journal (Refereed)
    Abstract [en]

    We studied the influence of 5 kDa poly(acrylic acid) (PAA) on the phase state, thermal properties, and lateral diffusion in bilayered systems of dimyristoylphosphatidylcholine (DMPC) using 31P NMR spectroscopy, differential scanning calorimetry (DSC), 1H NMR with a pulsed field gradient, and 1H nuclear Overhauser enhancement spectroscopy (NOESY). The presence of PAA does not change the lamellar structure of the system. 1H MAS NOESY cross-peaks observed for the interaction between lipid headgroups and polyion protons demonstrated only surface PAA−biomembrane interaction. Small concentrations of PAA (up to 4 mol %) lead to the appearance of a new lateral phase with a higher main transition temperature, a lower cooperativity, and a lower enthalpy of transition. Higher concentrations lead to the disappearance of measurable thermal effects. The lateral diffusion coefficient of DMPC and the apparent activation energy of diffusion gradually decreased at PAA concentrations up to around 4 mol %. The observed effects were explained by the formation of at least two types of PAA−DMPC lateral complexes as has been described earlier (Fujiwara, M.; Grubbs, R. H.; Baldeschwieler, J. D. J. Colloid Interface Sci., 1997, 185, 210). The first one is characterized by a stoichiometry of around 28 lipids per polymer, which corresponds to the adsorption of the entire PAA molecule onto the membrane. Lipid molecules of the complex are exchanged with the “pure” lipid bilayer, with the lifetime of the complex being less than 0.1 s. The second type of DMPC−PAA complex is characterized by a stoichiometry of 6 to 7 lipids per polymer and contains PAA molecules that are only partially adsorbed onto the membrane. A decrease in the DMPC diffusion coefficient and activation energy for diffusion in the presence of PAA was explained by the formation of a new cooperative unit for diffusion, which contains the PAA molecule and several molecules of lipids.

  • 137.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Munavirov, Bulat
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Antzutkin, Oleg
    Institute of Physics, Kazan (Volga Region) Federal University.
    Phase transition, ordering and lateral diffusion in phospholipid bilayers in the presence of poly(ethylene oxide)2012In: Mendeleev communications (Print), ISSN 0959-9436, E-ISSN 1364-551X, Vol. 22, no 5, p. 250-251Article in journal (Refereed)
    Abstract [en]

    The thermal behaviour, molecular orientation and lateral diffusion in the bilayered systems of dimyristoylphosphatidylcholine (DMPC) in the presence of poly(ethylene oxide) (PEO) were studied by NMR and DSC techniques, and it was found that PEO decreases the melting temperature (of vesicles and flat multibilayers) and affects the degree of orientation of DMPC molecules relative to the bilayer normal, but it does not influence the lateral diffusion of DMPC molecules

  • 138.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Munavirov, Bulat
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gröbner, Gerhard
    Umeå universitet.
    Rudakova, Maya
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Lateral diffusion in equimolar mixtures of natural sphingomyelins with dioleoylphosphatidylcholine2012In: Magnetic Resonance Imaging, ISSN 0730-725X, E-ISSN 1873-5894, Vol. 30, no 3, p. 412-421Article in journal (Refereed)
    Abstract [en]

    Cellular membranes of mammals are composed of a complex assembly of diverse phospholipids. Sphingomyelin (SM) and phosphatidylcholine (PC) are important lipids of eukaryotic cellular membranes and neuronal tissues, and presumably participate in the formation of membrane domains, known as “rafts,” through intermolecular interaction and lateral microphase decomposition. In these two-dimensional membrane systems, lateral diffusion of lipids is an essential dynamic factor, which might even be indicative of lipid phase separation process. Here, we used pulsed field gradient nuclear magnetic resonance to study lateral diffusion of lipid components in macroscopically oriented bilayers composed of equimolar mixtures of natural SMs of egg yolk, bovine brain, bovine milk and dipalmitoylphosphatidylcholine (DPPC) with dioleoylphosphatidylcholine (DOPC). In addition, differential scanning calorimetry was used as a complementary technique to characterize the phase state of the lipid bilayers. In fully liquid bilayers, the lateral diffusion coefficients in both DOPC/DPPC and DOPC/SM systems exhibit mean values of the pure bilayers. For DOPC/SM bilayer system, this behavior can be explained by a model where most SM molecules form short-lived lateral domains with preferential SM–SM interactions occurring within them. However, for bilayers in the presence of their low-temperature gel phase, lateral diffusion becomes complicated and cannot simply be understood solely by a simple change in the liquid phase decomposition.

  • 139.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Rudakova, M. A.
    Kazan (Volga Region) Federal University, Kazan.
    Munavirov, B. V.
    Kazan (Volga Region) Federal University, Kazan.
    Lateral diffusion in sphingomyelin bilayers2010In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 48, no 12, p. 945-950Article in journal (Refereed)
    Abstract [en]

    Sphingomyelin (SM) is an important lipid of eukaryotic cellular membranes and neuronal tissues. We studied lateral diffusion in macroscopically oriented bilayers of synthetic palmitoylSM (PSM) and natural sphingomyelins of egg yolk (eSM), bovine brain (bSM) and bovine milk (mSM) by NMR pulsed field gradient (NMR PFG) in the temperature range of 50-60oC. We found that the mean values of lateral diffusion coefficients (LDCs) of SMs are 1.9-fold lower in comparison with dipalmitoylphosphatidylcholine, which is similar in molecular structure. This discrepancy could be explained by the characteristics of intermolecular SM interactions. The LDCs of different SMs differ: egg SM is most similar to PSM, both of them have a 10% higher LDC value in comparison with the two other natural SMs. Besides, all natural SMs show a complicated form of the spin-echo diffusion decay, which is an indicator of a distribution of LDC values in bilayers. This peculiarity was explained by broad distributions of fatty acid lengths of the natural SMs studied here, especially mSM and bSM. We confirmed the relationship between chain length and the LDC in bilayers by computer analysis of a set of 1H NMR spectra obtained by scanning the value of the pulsed field gradient: there is a correlation between lower LDC values and SM molecules with longer acyl chains. The most probable mechanisms by which long-chain SM molecules decrease their lateral diffusion relative to the average value are protrusion into the other side of the bilayer or lateral separation into areas that diverge with their LDCs.

  • 140.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Rudakova, Maya
    Kazan (Volga Region) Federal University, Kazan.
    Peculiarities of lateral diffusion of lipids in three-component bilayers2011In: Russian Journal of Physical Chemistry, ISSN 0036-0244, E-ISSN 1531-863X, Vol. 85, no 3, p. 513-518Article in journal (Refereed)
    Abstract [en]

    The lateral diffusion of lipid molecules in macroscopically oriented bilayers of mixed dioleoylphosphatidylcholine (DOPC), egg sphingomyeline (SM), and cholesterol (CHOL) and its dependence on cholesterol concentration and temperature was studied by NMR with pulsed field gradient. The system forms a lamellar liquid crystalline (LC) phase; in a certain range of temperatures and concentrations of cholesterol the system is separated into two subphases: a disordered LC phase (ld) enriched with DOPC, and an ordered phase (l0) enriched with SM. These are characterized by their own lateral diffusion coefficients (LDCs), which differ from one another by a factor of 1.5–5. The dependence of the LDCs in the phases on the cholesterol concentration was analyzed. There was no clear dependence for the disordered LC phase, but we found that LDCs tend to grow in the concentration range of 15–35 mol % of CHOL. This behavior could be due to the redistribution of lipid components as the concentration of CHOL increases, eventually leading to a rise in DOPC concentration in the lo phase. In the range of liquidphase domains, we observed no dependence of LDCs on the diffusion time typical of the restricted diffusion regime, due to spatial restraints in the system. This could be associated with the relatively large size of the domains, and with the domain capability of lateral diffusion in a surrounding continuous phase.

  • 141.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Taher, Mamoun
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Glavatskih, Sergei
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    NMR self-diffusion study of a phosphonium bis(mandelato)borate ionic liquid2013In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, no 23, p. 9281-9287Article in journal (Refereed)
    Abstract [en]

    Newly synthesized halogen-free boron based ionic liquids (hf-BILs) composed of chelated orthoborate anionsand phosphonium cations have hydrolytic stability, low melting point and outstanding wear and frictionreducing properties. We report here the peculiarities of self-diffusion in one representative from this class,trihexyltetradecylphosphonium bis(mandelato)borate, [P6,6,6,14][BMB], in the temperature range of itspractical interest, 20–100 1C. NMR techniques demonstrated complicated diffusional behaviour – the ionicliquid can exist in one or two liquid ‘‘phases’’. In the low-temperature range (20–50 1C), two phases coexistwhere the cations, [P6,6,6,14], are contained mainly in the phase with slower diffusion coefficients while theanions, [BMB], are in the phase with faster diffusion coefficients. Cations have lower diffusion coefficientswith a factor of 20 as compared with the anions, an effect which is caused by aggregation of cations intodomains due to so-called ‘‘hydrophobic interaction’’ of their hydrocarbon chains. As the temperature risesabove 60 1C, the two phases merge into one where both ions have equal diffusion coefficients. This iscaused by thermal motion making the cation domains smaller in size and more easily interacting withanions. As a result, anions and cations diffuse in this high-temperature range as a pair.

  • 142.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Skirda, Vladimir
    Kazan (Volga Region) Federal University, Kazan.
    Munavirov, Bulat
    Kazan (Volga Region) Federal University, Kazan.
    Sacharova, Anna
    Kazan (Volga Region) Federal University, Kazan.
    Mobility of molecules and diagram of the state of a glyceryl monooleate–water system according to NMR data2011In: Russian Journal of Physical Chemistry, ISSN 0036-0244, E-ISSN 1531-863X, Vol. 85, no 4, p. 573-583Article in journal (Refereed)
    Abstract [en]

    Transverse relaxation and selfdiffusion of molecules in a glyceryl monooleate (monoolein)–D2O system was studied using pulsed 1H NMR in a range of water concentrations from 10 to 30 wt % and a range of temperatures from 20 to 90°C. It was noted that selfdiffusion is described by one or two selfdiffusion coefficients, depending on the temperature and concentration of water, while NMRrelaxation has a complex form. It was determined that with a reduction in the transverse magnetization, a component that has a form similar to Gaussian and relaxation times of 70 to 250 mcs is observed at certain temperatures and concentrations of water, confirming the formation of structures in which glyceryl monooleate molecules (GM) are characterized by anisotropic rotational mobility. It was demonstrated that the ranges of the concentrations of water and temperature in which this component is observed correspond to liquidcrystalline phase for lamellar and inverse hexagonal structural organizations of lipids, according to the state diagram obtained by X-ray diffraction. In the state diagram fields corresponding to micellar and cubic structures (characterized by the isotropic rotation of GM molecules in the time scale of NMR), multiexponential attenuations of magnetization with average relaxation times were noted in the range of 10 to 200 ms. A number of features were discovered with the use of NMR: specimens always contain structures with isotropic rotational mobility in the presence of structures characterized by anisotropic rotational mobility; a change in the fraction of the structures with anisotropic rotational mobility takes place slowly over 5–15 degrees, not abruptly. Our conclusions regarding the polymorphism of a GM–D2O system in the presence of anisotropic structures was confirmed by an analysis of the transverse NMR relaxation in an egg phosphatidylcholine–D2O system, for which the presence of only lamellar liquidcrystalline structure is recorded in 31P NMR.

  • 143.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Syleymanova, A.
    Gröbner, A.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    NMR study of oligomeric state and molecular mobility of aggregating proteins2008Conference paper (Refereed)
  • 144.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Taher, Mamoun
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Glavatskih, Sergei
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    The effect of the cation alkyl chain length on density and diffusion in dialkylpyrrolidinium bis(mandelato)borate ionic liquids2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 48, p. 26798-26805Article in journal (Refereed)
    Abstract [en]

    The physicochemical properties of ionic liquids are strongly affected by the selective combination of the cations and anions comprising the ionic liquid. In particular, the length of the alkyl chains of ions has a clear influence on the ionic liquid's performance. In this paper, we study the self-diffusion of ions in a series of halogen-free boron-based ionic liquids (hf-BILs) containing bis(mandelato)borate anions and dialkylpyrrolidinium cations with long alkyl chains CnH2n+1 with n from 4 to 14 within a temperature range of 293-373 K. It was found that the hf-BILs with n = 4-7 have very similar diffusion coefficients, while hf-BILs with n = 10-14 exhibit two liquid sub-phases in almost the entire temperature range studied (293-353 K). Both liquid sub-phases differ in their diffusion coefficients, while values of the slower diffusion coefficients are close to those of hf-BILs with shorter alkyl chains. To explain the particular dependence of diffusion on the alkyl chain length, we examined the densities of the hf-BILs studied here. It was shown that the dependence of the density on the number of CH2 groups in long alkyl chains of cations can be accurately described using a "mosaic type" model, where regions of long alkyl chains of cations (named 'aliphatic' regions) and the residual chemical moieties in both cations and anions (named 'ionic' regions) give additive contributions. Changes in density due to an increase in temperature and the number of CH2 groups in the long alkyl chains of cations are determined predominantly by changes in the free volume of the 'ionic' regions, while 'aliphatic' regions are already highly compressed by van der Waals forces, which results in only infinitesimal changes in their free volumes with temperature.

  • 145.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Research at the interface between industrial needs and scientific demands2004In: Proceedings, International Seminar on Mineral Processing Technology (MPT-2004): 19 - 21 February 2004 / [ed] G.V. Rao; V.N. Misra, New Delhi: Allied Publishers Ltd , 2004Conference paper (Refereed)
  • 146.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Utveckling av aluminiumoxidstabilisering1989Report (Other academic)
  • 147.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Vad ska vi göra med kärnkraftsavfallet?2003In: THULE: Kungl. Skytteanska Samfundets Årsbok 2003, Umeå: Kungl. Skytteanska samfundet , 2003, p. 161-172Chapter in book (Other (popular science, discussion, etc.))
  • 148. Forsling, Willis
    et al.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Betydelsen av grundläggande forskning för mineraltekniska processer2006In: Konferens i mineralteknik / [ed] Marianne Thomaeus; Eric Forssberg, Föreningen Mineralteknisk Forskning / Swedish Mineral Processing Research Association , 2006Conference paper (Other academic)
  • 149.
    Forsling, Willis
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Samskog, Per-Olof
    Research at the interface between industrial needs and scientific demands2005In: Bergsmannen med Jernkontorets Annaler, ISSN 0284-0448, no 3, p. 49-52Article in journal (Other academic)
  • 150.
    Forsling, Willis
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sjöberg, Staffan
    Avdelningen för oorganisk kemi, Umeå universitet.
    Ytkomplexbildning vid sulfidmineralflotation1989In: Konferens i mineralteknik: Luleå 14-16 februari 1989 / [ed] Börje Sköld; Eric Forssberg, MinFo , 1989, p. 83-96Conference paper (Other academic)
1234567 101 - 150 of 593
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