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  • 51.
    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.

  • 52.
    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.

  • 53.
    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)
  • 54.
    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.

  • 55.
    Javed, Muhammad Asadullah
    et al.
    NMR Research Unit, University of Oulu.
    Ahola, Susanna
    NMR Research Unit, University of Oulu.
    Håkansson, Pär
    NMR Research Unit, University of Oulu.
    Mankinen, Otto
    NMR Research Unit, University of Oulu.
    Aslam, Muhammad Kamran
    NMR Research Unit, University of Oulu.
    Filippov, Andrei
    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
    System and Component Design, Department of Machine Design, KTH Royal Institute of Technology.
    Antzutkin, Oleg N.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Telkki, Ville-Veikko
    NMR Research Unit, University of Oulu.
    Y Structure and dynamics elucidation of ionic liquids using multidimensional Laplace NMR2017In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 53, no 80, p. 11056-11059Article in journal (Refereed)
    Abstract [en]

    We demonstrate the ability of multidimensional Laplace NMR (LNMR), comprising relaxation and diffusion experiments, to reveal essential information about microscopic phase structures and dynamics of ionic liquids that is not observable using conventional NMR spectroscopy or other techniques.

  • 56.
    Kotenkov, Sergey A.
    et al.
    Institute of Physics, Kazan Federal University, Kazan, Russia.
    Gnezdilov, Oleg I.
    Institute of Physics, Kazan Federal University, Kazan, Russia.
    Khaliullina, Aliya V.
    Institute of Physics, Kazan Federal University, Kazan, Russia;Kazan State Medical University, Kazan, Russia.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Gimatdinov, Roustam S.
    Kazan State Medical University, Kazan, Russia.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Institute of Physics, Kazan Federal University, Kazan, Russia.
    Effect of Cholesterol and Curcumin on Ordering of DMPC Bilayers2019In: Applied Magnetic Resonance, ISSN 0937-9347, E-ISSN 1613-7507, Vol. 50, no 1-3, p. 511-520Article in journal (Refereed)
    Abstract [en]

    In this work, we compared the effects of curcumin and cholesterol directly competing to insert into the DMPC lipid bilayer during bilayer formation from an initially non-ordered state. 2H and 14N nuclear magnetic resonance spectroscopy showed that curcumin is not embedded deep in the lipid bilayer and interacts mainly with the head group of the lipid. In a more complex system of DMPC/CHOL/CUR, curcumin amplifies the effect of cholesterol on the ordering of lipid acyl chains.

  • 57.
    Lendel, Christofer
    et al.
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences (SLU).
    Bjerring, Morten
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences (SLU).
    Dubnovitsky, Anatoly
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences (SLU).
    Kelly, Robert T.
    Department of Physics, Warwick University, Coventry.
    Filippov, Andrei
    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.
    Nielsen, Niels Chr.
    Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University.
    Härd, Torleif
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences (SLU).
    A Hexameric Peptide Barrel as Building Block of Amyloid-β Protofibrils2014In: Angewandte Chemie, ISSN 0044-8249, E-ISSN 1521-3757, Vol. 126, no 47, p. 12970-12974Article in journal (Refereed)
    Abstract [en]

    Oligomeric and protofibrillar aggregates formed by the amyloid-β peptide (Aβ) are believed to be involved in the pathology of Alzheimer’s disease. Central to Alzheimer pathology is also the fact that the longer Aβ42 peptide is more prone to aggregation than the more prevalent Aβ40. Detailed structural studies of Aβ oligomers and protofibrils have been impeded by aggregate heterogeneity and instability. We previously engineered a variant of Aβ that forms stable protofibrils and here we use solid-state NMR spectroscopy and molecular modeling to derive a structural model of these. NMR data are consistent with packing of residues 16 to 42 of Aβ protomers into hexameric barrel-like oligomers within the protofibril. The core of the oligomers consists of all residues of the central and C-terminal hydrophobic regions of Aβ, and hairpin loops extend from the core. The model accounts for why Aβ42 forms oligomers and protofibrils more easily than Aβ40.

  • 58.
    Lendel, Christofer
    et al.
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences (SLU).
    Bjerring, Morten
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences (SLU).
    Dubnovitsky, Anatoly
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences (SLU).
    Kelly, Robert T.
    Department of Physics, Warwick University, Coventry.
    Filippov, Andrei
    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.
    Nielsen, Niels Chr.
    Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University.
    Härd, Torleif
    Department of Chemistry and Biotechnology, Swedish University of Agricultural Sciences (SLU).
    A Hexameric Peptide Barrel as Building Block of Amyloid-β Protofibrils2014In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 53, no 47, p. 12756-12760Article in journal (Refereed)
    Abstract [en]

    Oligomeric and protofibrillar aggregates formed by the amyloid-β peptide (Aβ) are believed to be involved in the pathology of Alzheimer’s disease. Central to Alzheimer pathology is also the fact that the longer Aβ42 peptide is more prone to aggregation than the more prevalent Aβ40. Detailed structural studies of Aβ oligomers and protofibrils have been impeded by aggregate heterogeneity and instability. We previously engineered a variant of Aβ that forms stable protofibrils and here we use solid-state NMR spectroscopy and molecular modeling to derive a structural model of these. NMR data are consistent with packing of residues 16 to 42 of Aβ protomers into hexameric barrel-like oligomers within the protofibril. The core of the oligomers consists of all residues of the central and C-terminal hydrophobic regions of Aβ, and hairpin loops extend from the core. The model accounts for why Aβ42 forms oligomers and protofibrils more easily than Aβ40.

  • 59.
    Munavirov, Bulat
    et al.
    Kazan (Volga Region) Federal University, Kazan.
    Gnezdilov, Oleg
    Kazan (Volga Region) Federal University, Kazan.
    Rudakova, Maya
    Kazan (Volga Region) Federal University, Kazan.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Interaction of polyacrylic acid with lipid bilayers: effect of polymer mass2013In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 51, no 11, p. 750-755Article in journal (Refereed)
    Abstract [en]

    Polyanion-coated lipid vesicles are proposed to have an appreciable potential for drug delivery because of their ability to control the permeability of lipid bilayers by environmental parameters such as pH and temperature. However, details of the interaction of this class of polymers with lipids and their mechanisms of induced permeability are still being debated. In this work, we applied 1H NOESY to study details of the interaction of polyacrylic acid (PAA) fractions of molecular weights 5 and 240 kDa with dimyristoylphosphatidylcholine vesicles. We showed that PAA of two different molecular masses modifies lipid bilayers increasing disorder and probability of close contact between polar and hydrophobic groups. PAA molecules adsorb near the interface of lipid bilayers but do not penetrate into the hydrophobic core of the bilayer and, thus, cannot participate in formation of transbilayer channels, proposed in earlier works. Increasing the molecular mass of PAA from 5 kDa to 240 kDa does not change the effect of PAA on the bilayer, although PAA240 forms a more compact structure (either intra-molecular or inter-molecular) and interacts more strongly with interface lipid protons

  • 60.
    Munavirov, Bulat V.
    et al.
    Institute of Physics, Kazan (Volga Region) Federal University.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rudakova, Maya A.
    Institute of Physics, Kazan (Volga Region) Federal University.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Polyacrylic Acid Modifies Local and Lateral Mobilities in Lipid Membranes2014In: Journal of Dispersion Science and Technology, ISSN 0193-2691, E-ISSN 1532-2351, Vol. 35, no 6, p. 848-858Article in journal (Refereed)
    Abstract [en]

    promising polymer for engineering lipid-based drug-delivery vesicles. Its unique properties allow lowering drug dose and delivery the drug close to the site of its release. To design a successful delivery scheme, however, it is important to understand on the molecular scale how the polymer interacts with lipids under various conditions in the human body. Some aspects of the PAA-lipid interaction can be revealed using physical methods, such as differential scanning microscopy, nuclear magnetic resonance spectroscopy, NMR-diffusometry and infrared spectroscopy. This work discusses the use of these techniques as well as the peculiarities of preparing vesicular and microscopically aligned PAA-lipid systems.

  • 61.
    Norlin, Nils
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hellberg, M.
    Luleå tekniska universitet.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sousa, A.A.
    National Institutes of Health, Bethesda.
    Gröbner, G.
    Umeå universitet.
    Leapman, R.D.
    National Institutes of Health, Bethesda.
    Almqvist, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Aggregation and fibril morphology of the Arctic mutation of Alzheimer's Aβ peptide by CD, TEM, STEM and in situ AFM2012In: Journal of Structural Biology, ISSN 1047-8477, E-ISSN 1095-8657, Vol. 180, no 1, p. 174-189Article in journal (Refereed)
    Abstract [en]

    Morphology of aggregation intermediates, polymorphism of amyloid fibrils and aggregation kinetics of the "Arctic" mutant of the Alzheimer's amyloid β-peptide, Aβ (1-40)(E22G), in a physiologically relevant Tris buffer (pH 7.4) were thoroughly explored in comparison with the human wild type Alzheimer's amyloid peptide, wt-Aβ (1-40), using both in situ atomic force and electron microscopy, circular dichroism and thioflavin T fluorescence assays. For arc-Aβ (1-40) at the end of the 'lag'-period of fibrillization an abrupt appearance of ∼3 nm size 'spherical aggregates' with a homogeneous morphology, was identified. Then, the aggregation proceeds with a rapid growth of amyloid fibrils with a variety of morphologies, while the spherical aggregates eventually disappeared during in situ measurements. Arc-Aβ (1-40) was also shown to form fibrils at much lower concentrations than wt-Aβ (1-40): ≤2.5 μM and 12.5 μM, respectively. Moreover, at the same concentration, 50 μM, the aggregation process proceeds more rapidly for arc-Aβ (1-40): the first amyloid fibrils were observed after c.a. 72 h from the onset of incubation as compared to approximately 7 days for wt-Aβ (1-40). Amyloid fibrils of arc-Aβ (1-40) exhibit a large variety of polymorphs, at least five, both coiled and non-coiled distinct fibril structures were recognized by AFM, while at least four types of arc-Aβ (1-40) fibrils were identified by TEM and STEM and their mass-per-length statistics were collected suggesting supramolecular structures with two, four and six β-sheet laminae. Our results suggest a pathway of fibrillogenesis for full-length Alzheimer's peptides with small and structurally ordered transient spherical aggregates as on-pathway immediate precursors of amyloid fibrils.

  • 62.
    Shah, Faiz Ullah
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bhattacharyya, Shubhankar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Akhtar, Farid
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Ionic Liquids As Liquid And Solid Sorbents For Post-Combustion CO2 Capture2016Conference paper (Refereed)
  • 63.
    Shah, Faiz Ullah
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Oleg, Gnezdilov
    Institute of Physics, Kazan Federal University .
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Institute of Physics, Kazan Federal University.
    Ion dynamics in halogen-free phosphonium bis(salicylato)borate ionic liquid electrolytes for lithium-ion batteries2017In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 25, p. 16721-16730Article in journal (Refereed)
    Abstract [en]

    This study was focused on the investigation of ion dynamics in halogen-free, hydrophobic, and hydrolytically stable phosphonium bis(salicylato)borate [P4,4,4,8][BScB] ionic liquid electrolytes for lithium-ion batteries. The structure and purity of the synthesized ionic liquid and lithium bis(salicylato)borate Li[BScB] salt were characterized using 1H, 13C, 31P, and 11B NMR spectroscopy. The Li[BScB] salt was mixed with an ionic liquid at the concentrations ranging from 2.5 mol% to 20 mol%. The physicochemical properties of the resulting electrolytes were characterized using thermal analysis (TGA and DSC), electrical impedance spectroscopy, and pulsed-field gradient (PFG) NMR and ATR-FTIR spectroscopy. The apparent transfer numbers of the individual ions were calculated from the diffusion coefficients of the cation and anion as determined via the PFG NMR spectroscopy. NMR and ATR-FTIR spectroscopic techniques revealed dynamic interactions between the lithium cation and bis(salicylato)borate anion in the electrolytes. The ion–ion interactions were found to increase with the increasing concentration of the Li[BScB] salt, which resulted in ionic clustering at the concentrations higher than 15 mol% of Li salt in the ionic liquid.

  • 64.
    Shah, Faiz Ullah
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Oleg I., Gnezdilov
    Institute of Physics, Kazan Federal University, 420008, Kazan, Russia.
    Rashi, Gusain
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Institute of Physics, Kazan Federal University, Russia.
    Transport and Association of Ions in Lithium Battery Electrolytes Based on Glycol Ether Mixed with Halogen-Free Orthoborate Ionic Liquid2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 16340Article in journal (Refereed)
    Abstract [en]

    Ion transport behaviour of halogen-free hybrid electrolytes for lithium-ion batteries based on phosphonium bis(salicylato)borate [P4,4,4,8][BScB] ionic liquid mixed with diethylene glycol dibutyl ether (DEGDBE) is investigated. The Li[BScB] salt is dissolved at different concentrations in the range from 0.15 mol kg−1 to 1.0 mol kg−1 in a mixture of [P4,4,4,8][BScB] and DEGDBE in 1:5 molar ratio. The ion transport properties of the resulting electrolytes are investigated using viscosity, electrical impedance spectroscopy and pulsed-Field Gradient (PFG) NMR. The apparent transfer numbers of ions are calculated from the diffusion coefficients measured by using PFG NMR. PFG NMR data suggested ion association upon addition of Li salt to the [P4,4,4,8][BScB] in DEGDBE solution. This is further confirmed by liquid state 7Li and 11B NMR, and FTIR spectroscopic techniques, which suggest strong interactions between the lithium cation and oxygen atoms of the [BScB]− anion in the hybrid electrolytes.

  • 65.
    Taher, Mamoun
    et al.
    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.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Baets, Patrick De
    Department of Mechanical Construction and Production, Ghent University.
    Glavatskih, Sergei
    Department of Mechanical Construction and Production, Ghent University.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Halogen-free pyrrolidinium bis(mandelato)borate ionic liquids: some physicochemical properties and lubrication performance as additives to polyethylene glycol2014In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 58, p. 30617-30623Article in journal (Refereed)
    Abstract [en]

    This work reports on the synthesis and physicochemical characterisation of novel halogen-free boron containing ionic liquids (hf-BILs) with dialkylpyrrolidinium cations [CnC1Pyrr]+, n ¼ 4–14, and bis(mandelato)borate anion [BMB]. All the synthesised compounds are liquids at room temperature. It was found that the thermal properties and density of these hf-BILs are affected by the length of the longest alkyl chain connected to the nitrogen atom in the pyrrolidinium cations. Differential scanning calorimetry measurements revealed that glass transition temperatures of these ionic liquids are in the temperature range from 218 to 241 K. Interestingly, the glass transition temperatures follow the “odd– even” effect related to the number of carbons (n) in one of the alkyl chains of [CnC1Pyrr]+. It was also found that hf-BILs' density decreases with an increase in the alkyl chain length of [CnC1Pyrr]+. It is suggested that the “odd–even” effect is associated with the difference in packing and specific interactions of cations and anions of this class of hf-BILs. Their lubricating properties, as 3 wt% additives in polyethylene glycol (PEG), were evaluated in steel–steel contacts. PEG with hf BILs additive provided significantly lower wear and friction compared to the neat PEG and 5W40 engine oil. It was found that shortening the length of the longest alkyl chain in the cations of [CnC1Pyrr][BMB] significantly reduces frictional losses. Antiwear properties of [CnC1Pyrr][BMB] in PEG follow the same trend.

  • 66.
    Taher, Mamoun
    et al.
    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.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Glavatskih, Sergei
    Machine Design, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Halogen-free ionic liquids in lubrication2014Conference paper (Refereed)
    Abstract [en]

    The use of wear-resistant non-ferrous and lightweight materials calls for novel types of lubricants including neat Ionic Liquids (ILs) and ILs as additives to base oils [1-4]. ILs are non-flammable low temperature molten salts, which have negligible volatility and a high thermal stability. However, most of previously studied ILs as promising lubricants contain BF4- or PF6- anions, which are prone to hydrolysis producing corrosive and toxic species. Here we report on the synthesis, physic-chemical and tribological characterisation of halogen-free ILs with cations belonging to different families (phosphonium, pyrrolidinium, imidazolium), combined with different orthoborate anions (bis(mandelato)borate [BMB], bis(salicylato)borate, bis(oxalato)borate, etc). It was found that these types of hf-BILs (both as neat liquids and as additives) outperform a fully formulated engine oil and a neat PEG oil as antiwear and friction reducing lubricants at steel-steel and steel-aluminium contacts.To reveal mechanisms of formation of tribofilms, the mechanochemically induced boundary films on surfaces of Al2O3, MgO and SiO2 in contact with orthoborate-based ILs were characterised using solid-state multinuclear (11B, 31P and 29Si) MAS NMR, FTIR and Raman spectroscopy. It was found that some of these ILs interact with the oxides, in particular, at elevated temperatures. We suggest that the boundary film formation between hf-BILs and -Al2O3, MgO and SiO2 surfaces is a complex process involving various chemical reactions at the solid-liquid interfaces. Self-diffusion of ionic species in orthoborate based ILs and in IL/PEG mixtures as a function of temperature was studied using pulse-field-gradient (PFG) 1H and 31P NMR [5]. It was found that [P66614][BMB] can exist in one or two different liquid “phases” with ionic species having dramatically different (by two orders of magnitude) self-diffusion coefficients: Slowly diffusing phosphonium cations with long and bulky alkyl chains form domains stabilised by hydrophobic interactions in these ILs in the temperature range 20-50 oC, while small orthoborate anions are fast diffusing species at these temperatures [5]. These domains are, however, disrupted by developed molecular motion with the cation-anion complexes having one and the same diffusion coefficient when the IL system is heated above 50oC. A similar phenomenon was also found in some other [BMB] based ILs with pyrrolidinium and imidazolium cations.

  • 67.
    Usachev, Konstantin S.
    et al.
    Kazan (Volga Region) Federal University, Kazan.
    Efimov, Sergej V.
    Kazan (Volga Region) Federal University, Kazan.
    Yulmetov, Ajdar R.
    Kazan (Volga Region) Federal University, Kazan.
    Filippov, Andrei
    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.
    Afonin, Sergei
    Karlsruhe Institute of Technology.
    Klochkov, vladimir V.
    Kazan (Volga Region) Federal University, Kazan.
    Spatial structure of heptapeptide Aβ 16-22 (beta-amyloid Aβ 1-40 active fragment) in solution and in complex with a biological membrane model2012In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 50, no 12, p. 784-792Article in journal (Refereed)
    Abstract [en]

    The spatial structure of an active fragment of beta-amyloid Aβ 1-40 heptapeptide Aβ 16-22 (Lys-Leu-Val-Phe-Phe-Ala-Glu) in aqueous buffer solution and in complex with sodium dodecyl sulfate micelles as a model membrane system was investigated by 1H NMR spectroscopy and two-dimensional NMR (TOCSY, HSQC-HECADE (Heteronuclear Couplings from ASSCI-domain experiments with E.COSY-type crosspeaks), NOESY) spectroscopy. Complex formation was confirmed by the chemical shift changes of the heptapeptide's 1H NMR spectra, as well as by the signs and values of the NOE effects in different environments. We compared the spatial structure of the heptapeptide in borate buffer solution and in complex with a model of the cell surface membrane

  • 68.
    Usachev, Konstantin S.
    et al.
    Kazan (Volga Region) Federal University, Kazan.
    Efimov, Sergej V.
    Kazan (Volga Region) Federal University, Kazan, Institute of Physics, Kazan (Volga Region) Federal University.
    Kolosova, O.A.
    Kazan (Volga Region) Federal University, Kazan.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Klochkov, Vladimir V.
    Institute of Physics, Kazan (Volga Region) Federal University.
    High-resolution NMR structure of the antimicrobial peptide protegrin-2 in the presence of DPC micelles2015In: Journal of Biomolecular NMR, ISSN 0925-2738, E-ISSN 1573-5001, Vol. 61, no 3-4, p. 227-234Article in journal (Refereed)
    Abstract [en]

    PG-1 adopts a dimeric structure in dodecylphosphocholine (DPC) micelles, and a channel is formed by the association of several dimers but the molecular mechanisms of the membrane damage by non-α-helical peptides are still unknown. The formation of the PG-1 dimer is important for pore formation in the lipid bilayer, since the dimer can be regarded as the primary unit for assembly into the ordered aggregates. It was supposed that only 12 residues (RGGRL-CYCRR-RFCVC-V) are needed to endow protegrin molecules with strong antibacterial activity and that at least four additional residues are needed to add potent antifungal properties. Thus, the 16-residue protegrin (PG-2) represents the minimal structure needed for broad-spectrum antimicrobial activity encompassing bacteria and fungi. As the peptide conformation and peptide-to-membrane binding properties are very sensitive to single amino acid substitutions, the solution structure of PG-2 in solution and in a membrane mimicking environment are crucial. In order to find evidence if the oligomerization state of PG-1 in a lipid environment will be the same or not for another protegrins, we investigate in the present work the PG-2 NMR solution structure in the presence of perdeuterated DPC micelles. The NMR study reported in the present work indicates that PG-2 form a well-defined structure (PDB: 2MUH) composed of a two-stranded antiparallel β-sheet when it binds to DPC micelles.

  • 69.
    Usachev, Konstantin S.
    et al.
    Kazan (Volga Region) Federal University, Kazan.
    Filippov, Andrei
    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.
    Klochkov, Vladimir V.
    Kazan (Volga Region) Federal University, Kazan.
    Spatial structure of beta-amyloid Aβ1-40 in complex with a biological membrane model2012In: Advances in Alzheimer's Disease, ISSN 2169-2459, Vol. 1, no 3, p. 22-29Article in journal (Refereed)
    Abstract [en]

    The spatial structure of beta-amyloid Aβ1-40 in complex with sodium dodecyl sulfate micelles as a model membrane system was investigated by 1H-1H two-dimensional NMR (TOCSY, NOESY) spectroscopy and molecular dynamic method calculations. On the basis of NOE and chemical shifts changes data, spatial structure of the com- plex beta-amyloid-model of the cell surface membrane was obtained.

  • 70.
    Usachev, Konstatin S.
    et al.
    Kazan (Volga Region) Federal University, Kazan.
    Filippov, Andrei
    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.
    Klochkov, Vladimir V.
    Kazan (Volga Region) Federal University, Kazan.
    Use of a combination of the RDC method and NOESY NMR spectroscopy to determine the structure of Alzheimer's amyloid Aβ10-35 peptide in solution and in SDS micelles2013In: European Biophysics Journal, ISSN 0175-7571, E-ISSN 1432-1017, Vol. 42, no 11-12, p. 803-810Article in journal (Refereed)
    Abstract [en]

    The spatial structure of Alzheimer's amyloid Aβ10-35-NH2 peptide in aqueous solution at pH 7.3 and in SDS micelles was investigated by use of a combination of the residual dipolar coupling method and two-dimensional NMR spectroscopy (TOCSY, NOESY). At pH 7.3 Aβ10-35-NH2 adopts a compact random-coil conformation whereas in SDS micellar solutions two helical regions (residues 13-23 and 30-35) of Aβ10-35-NH2 were observed. By use of experimental data, the structure of "peptide-micelle" complex was determined; it was found that Aβ10-35-NH2 peptide binds to the micelle surface at two regions (residues 17-20 and 29-35). © 2013 European Biophysical Societies' Association.

  • 71.
    Usachev, Konstatin S.
    et al.
    Kazan (Volga Region) Federal University, Kazan.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Khairutdinov, B.I.
    Kazan (Volga Region) Federal University, Kazan.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Klochkov, V.V.
    Kazan (Volga Region) Federal University, Kazan.
    NMR structure of the Arctic mutation of the Alzheimer’s Aβ(1-40) peptide docked to SDS micelles2014In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 1076, p. 518-523Article in journal (Refereed)
    Abstract [en]

    The “Arctic” point mutation of the Alzheimeŕs amyloid β-peptide is a rare mutation leading to an early onset of Alzheimeŕs disease. The peptide may interact with neuronal membranes, where it can provide its toxic effects. We used 2D NMR spectroscopy to investigate the conformation of the “Arctic” mutant of Aβ1-40 Alzheimer’s amyloid peptide in sodium dodecyl sulfate micelle solutions, which are the type of amphiphilic structures mimicking some properties of biomembranes. The study showed that the Arctic mutant of Aβ1-40 interacts with the surface of SDS micelles mainly through the Leu17-Asn27 310-helical region, while the Ile31-Val40 region is buried in the hydrophobic interior of the micelle. In contrast, wild-type Aβ1-40 interacts with SDS micelles through the Lys16-Asp23 α-helical region and Gly29-Met35. Both the Arctic mutant and the wild-type Aβ1-40 peptides interactions with SDS micelles are hydrophobic in nature. Aβ peptides are thought to be capable of forming pores in biomembranes that can cause changes in neuronal and endothelial cell membrane permeability. It has also been shown that Aβ peptides containing the “Arctic” mutation are more neurotoxic and aggregate more readily than the wild-type Aβ peptides at physiological conditions. Here, we propose that the extension of the helical structure of Leu17-Asn27 and a high aliphaticity (neutrality) of the C-terminal region in the Arctic Aβ peptides are consistent with the idea that formation of ion-permeable pores by Aβ oligomers may be one of prevailing mechanisms of a larger neuronal toxicity of the Arctic Aβ compared to the wild-type Aβ peptides, independent of oxidative damage and lipid peroxidation.

  • 72.
    Usachev, K.S.
    et al.
    Kazan (Volga Region) Federal University, Kazan.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Filippova, E.A.
    Kazan (Volga Region) Federal University, Kazan.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Klochkov, V.V.
    Kazan (Volga Region) Federal University, Kazan.
    Solution structures of Alzheimer’s amyloid Aβ13-23 peptide: NMR studies in solution and in SDS2013In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 1049, p. 436-440Article in journal (Refereed)
    Abstract [en]

    To be believed that interaction of amyloid peptides with the cellular membrane is one of the mechanisms for the neurotoxicity of Aβ. Therefore, structural studies of beta-amyloid in solution and in a “peptide - bio-membrane” complex are of intense interest. The aim of this study was to acquire a better understanding of the mechanism of “Aβ peptide-micelle surface” complex formation. Previous studies of Aβ peptides binding on the micelle surface show the presence of helical region between 15-24 residues and that fragment between 11-28 residues have a tendency to exit the hydrophobic environment of the micelle core and to bind to the micelle surface. In present paper we considered the fragment of Aβ from 13 to 23 residues and found that L17, F19 and F20 residues region play a great role in the process of binding of Aβ to the micelle surface.

  • 73.
    Wei, Juan
    et al.
    Department of Chemistry and Department of Physics, University of Warwick, Coventry.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Iuga, Dinu
    Department of Physics, Warwick University, Coventry, Department of Chemistry and Department of Physics, University of Warwick, Coventry.
    Lam, Pui Yiu
    Department of Chemistry and Department of Physics, University of Warwick, Coventry.
    Barrow, Mark P.
    Department of Chemistry and Department of Physics, University of Warwick, Coventry.
    Dupree, Ray
    University of Warwick, Department of Physics, Warwick University, Coventry, Department of Chemistry and Department of Physics, University of Warwick, Coventry.
    Brown, Steven P.
    Department of Physics, Warwick University, Coventry, Department of Chemistry and Department of Physics, University of Warwick, Coventry.
    O'Connor, Peter B.
    Department of Chemistry and Department of Physics, University of Warwick, Coventry.
    Amyloid Hydrogen Bonding Polymorphism Evaluated by 15N{17O}REAPDOR Solid-State NMR and Ultra-High Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry2016In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 55, no 14, p. 2065-2068Article in journal (Refereed)
    Abstract [en]

    A combined approach, using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and solid-state NMR (Nuclear Magnetic Resonance), shows a high degree of polymorphism exhibited by Aβ species in forming hydrogen-bonded networks. Two Alzheimer’s Aβ peptides, Ac-Aβ16–22-NH2 and Aβ11–25, selectively labeled with 17O and 15N at specific amino acid residues were investigated. The total amount of peptides labeled with 17O as measured by FTICR-MS enabled the interpretation of dephasing observed in 15N{17O}REAPDOR solid-state NMR experiments. Specifically, about one-third of the Aβ peptides were found to be involved in the formation of a specific >C═17O···H–15N hydrogen bond with their neighbor peptide molecules, and we hypothesize that the rest of the molecules undergo ± n off-registry shifts in their hydrogen bonding networks.

12 51 - 73 of 73
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