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  • 1.
    Ahmed, Hamzah
    et al.
    Luleå University of Technology, Department of Health Sciences, Medical Science.
    Shimpi, Manishkumar R.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Velaga, Sitaram P.
    Luleå University of Technology, Department of Health Sciences, Medical Science.
    Relationship between mechanical properties and crystal structure in cocrystals and salt of paracetamol2017In: Drug Development and Industrial Pharmacy, ISSN 0363-9045, E-ISSN 1520-5762, Vol. 43, no 1, p. 89-97Article in journal (Refereed)
    Abstract [en]

    Objectives were to study mechanical properties of various solid forms of paracetamol and relate to their crystal structures. Paracetamol Form I (PRA), its cocrystals with oxalic acid (PRA-OXA) and 4,4-bipyridine (PRA-BPY) and hydrochloride salt (PRA-HCL) were selected. Cocrystals and salt were scaled-up using rational crystallization methods. The resulting materials were subjected to differential scanning solid-state characterization. The powders were sieved and 90-360 µm sieve fraction was considered. These powders were examined by scanning electron microscopy (SEM) and densities were determined. Tablets were made at applied pressures of 35-180 MPa under controlled conditions and the tablet height, diameter and hardness were measured. Tensile strength and porosity of the tablets were estimated using well known models. Crystal structures of these systems were visualized and slips planed were identified. Cocrystal and salt of PRA were physically pure. Sieved powders had comparable morphologies and particle size. The apparent and theoretical densities of powders were similar but no clear trends were observed. The tensile strengths of these compacts were increased with increasing pressure whereas tabletability decreased in the order oxalic acid > PRA-HCL ≈ PRA-OXA > BPY > PRA-BPY. Tablet tensile strength decreases exponentially with increasing porosity with the exception of PRY-BPY and BPY. Slip plane prediction based on attachment energies may not be independently considered. However, it was possible to explain the improved mechanical properties of powders based on the crystal structure. Cocrystallization and salt formation have introduced structural features that are responsible for improved tableting properties of PRA.

  • 2.
    An, Rong
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing.
    Zhou, Guobing
    School of Chemical Biological and Materials Engineering, University of Oklahoma.
    Zhu, Yudan
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University.
    Zhu, Wei
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University.
    Huang, Liangliang
    School of Chemical Biological and Materials Engineering, University of Oklahoma.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Friction of Ionic Liquid–Glycol Ether Mixtures at Titanium Interfaces: Negative Load Dependence2018In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 5, no 14, article id 1800266Article in journal (Refereed)
    Abstract [en]

    Structural reorientation of alkyl chains in the phosphonium cation of orthoborate ionic liquid mixed with glycol ether occurs with increasing normal load of the AFM tip. The flat reoriented structure, similar to the ‘blooming lotus leaf’, produces a new sliding interface that is responsible for the observed lower friction at higher loads. This work is reported by Rong An, Liangliang Huang, Faiz Ullah Shah and co‐workers in article number 1800263.

  • 3.
    An, Rong
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing.
    Zhou, Guobing
    School of Chemical Biological and Materials Engineering, University of Oklahoma.
    Zhu, Yudan
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University.
    Zhu, Wei
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University.
    Huang, Liangliang
    School of Chemical Biological and Materials Engineering, University of Oklahoma.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Friction of Ionic Liquid–Glycol Ether Mixtures at Titanium Interfaces: Negative Load Dependence2018In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 5, no 14, article id 1800263Article in journal (Refereed)
    Abstract [en]

    The atomic force microscopy experiments and nonequilibrium molecular dynamics (NEMD) simulations demonstrate a negative friction–load dependence to ionic liquid–glycol ether mixtures, that is, the friction decreases as the normal load increases. NEMD simulations reveal a structural reorientation of the studied ionic liquid (IL): as the normal load increases, the cation alkyl chains of ILs change the orientation to preferentially parallel to the tip scanning path. The flat‐oriented IL structures, similar to the “blooming lotus leaf,” produce a new sliding interface and reduce the friction. A further molecular dynamics simulation is carried out by adopting slit‐pore models to mimic the tip approaching process to confirm the dynamics of ILs. A faster diffusion of ILs in the smaller slit pore is observed. The faster diffusion of ILs in the more confined slit pore facilitates the structural reorientation of ILs. The resulted new sliding surface is responsible for the observed smaller friction at higher loads, also known as the negative friction–load dependence. These findings provide a fundamental explanation to the role of ILs in interfacial lubrications. They help to understand liquid flow properties under confinement, with implications for the development of better nanofluidic devices.

  • 4. Andren, Henrik
    et al.
    Rodushkin, Ilia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Stenberg, Anna
    Luleå tekniska universitet.
    Malinovskiy, Dmitry
    Baxter, Douglas
    Sources of mass bias and isotope ratio variation in multi-collector ICP-MS: optimization of instrumental parameters based on experimental observations2004In: Journal of Analytical Atomic Spectrometry, ISSN 0267-9477, E-ISSN 1364-5544, Vol. 19, no 9, p. 1217-1224Article in journal (Refereed)
    Abstract [en]

    In this work, several contributing factors to the observed mass bias in inductively coupled plasma mass spectrometry (ICP-MS) have been identified. Analyses of the isotopic compositions of B deposited on sampler and skimmer cones demonstrate enrichment of [1][0]B on the former and [1][1]B on the latter. Grounding the capacitive discharge system to enhance sensitivity also magnified the level of [1][1]B enrichment on the skimmer cone more than four-fold. This supersonic expansion of the ion beam behind the sampler is confirmed to be an important source of mass bias. Isotopic analyses of the Fe, Zn and Ti leached from used extraction lenses yielded a linear relationship between the levels of lighter isotope depletion and mass ratio. Although consistent with the space-charge effect, the fact that isotopically-heavy deposits were found demonstrates that the ion beam diverges into a relatively wide solid angle in the field-free region behind the skimmer. This severely impairs transmission of, in particular, the lighter isotopes. For a wide range of elements (Li, B, Fe, Ni, Cu, Sb, Ce, Hf and Re), the magnitude of the mass bias was found to be affected by the sample gas flow rate, as well as the distance between the sampler and the end of the torch, i.e., the sampling depth, employed in the Neptune multi-collector ICP-MS instrument. Mathematical analysis of the profiles of intensity variations as a function of these instrumental parameters revealed that the response peaks closer to the torch for the heavier isotopes of all studied elements. Owing to this spatial non-coincidence, tuning for maximum intensity on either isotope will result in sampling from a region where even slight plasma instabilities will be translated into substantial variations in mass bias. Therefore, in-plasma processes also contribute to the degree and temporal stability of mass bias. In light of these findings, recommendations for optimizing multi-collector ICP-MS with respect to obtaining the highest possible precision are presented.

  • 5.
    Andrén, Henrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Studies of artificial mass bias in isotopic measurements by inductively coupled plasma mass spectrometry2004Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Mass spectrometry, and especially inductively coupled plasma mass spectrometry (ICP-MS), suffers heavily from mass bias, or instrumental mass discrimination. The nett result of this effect is the preferential transmission, most often of heavier ions through the mass spectrometer. Most work regarding this phenomenon in ICP-MS dates back quite far, and has been interpreted in terms of the space-charge effect. This means that Coulombic forces acting on the beam of positively charged particles extracted from the ICP result in greater dissipation of lighter, and hence more mobile ions from the beam axis. In this work the importance of the space-charge effect as a universal explanation for mass bias is challenged by the results of high precision measurements of isotope ratios. Other than considering some commonly known sources of isotope ratio measurement bias, a not previously considered mechanism of isotopic fractionation has been investigated, i.e. diffusion in solution. It was established that, indeed, diffusion does lead to isotopic fractionation in solution, and although this is a long term process, may contribute to the minor isotopic variations observed in certain aquatic environments. Furthermore it was established that spectral interferences of argone oxide ions could be discerned from the ions of iron using high resolution ICP-MS, thus eliminating this potential source of artificial fractionation. Most significant was the discovery that the extent of mass bias varied throughout the volume of the plasma, and was further affected by sample characteristics, such as analyte concentration and acid strength. This identifies the plasma itself as the major source of instrumental mass discrimination. Varying the sampling position, i.e. the point at which ions are extracted from the plasma, not only affected the measured isotope ratios, but also the precision of such measurements. From these results, it is not recommended to measure at the sampling position providing maximum signal, since the variability in the isotope ratio is also at its' maximum there. Instead, the ions should be sampled from a point below the maximum, where the stability of the ratios will be better.

  • 6.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Amyloidosis of Alzheimer's A peptides: solid-state nuclear magnetic resonance, electron paramagnetic resonance, transmission electron microscopy, scanning transmission electron microscopy and atomic force microscopy studies2004In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 42, no 2, p. 231-246Article in journal (Refereed)
    Abstract [en]

    Aggregation cascade for Alzheimer's amyloid-β peptides, its relevance to neurotoxicity in the course of Alzheimer's disease and experimental methods useful for these studies are discussed. Details of the solid-phase peptide synthesis and sample preparation procedures for Alzheimer's β-amyloid fibrils are given. Recent progress in obtaining structural constraints on Aβ-fibrils from solid-state NMR and scanning transmission electron microscopy (STEM) data is discussed. Polymorphism of amyloid fibrils and oligomers of the 'Arctic' mutant of Aβ(1-40) was studied by 1H,13C solid-state NMR, transmission electron microscopy (TEM) and atomic force microscopy (AFM), and a real-time aggregation of different polymorphs of the peptide was observed with the aid of in situ AFM. Recent results on binding of Cu(II) ions and Al-citrate and Al-ATP complexes to amyloid fibrils, as studied by electron paramagnetic resonance (EPR) and solid-state 27Al NMR techniques, are also presented.

  • 7.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Molecular structure determination: applications in biology2002In: Solid state NMR spectroscopy: principles and applications, Oxford: Blackwell Science , 2002, p. 280-390Chapter in book (Other academic)
  • 8.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Polymorphism of Alzheimer´s A-beta Amyloid Fibrils2017In: Modern Magnetic Resonance / [ed] Graham A. Webb, Springer International Publishing , 2017, p. 1-15Chapter in book (Other academic)
    Abstract [en]

    An overview of the strategy and experimental solid-state NMR, STEM, and AFM methods useful for obtaining structural constraints on Alzheimer’s amyloid-β peptide fibrils is presented. Polymorphism of amyloid fibrils and the relevance to neurotoxicity is discussed.

  • 9.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Polymorphism of Alzheimer´s A-beta Amyloid Fibrils2006In: Modern Magnetic Resonance: Applications in Chemistry, Biological and Marine Sciences, Dordrecht: Encyclopedia of Global Archaeology/Springer Verlag, 2006, p. 15-23Chapter in book (Other academic)
    Abstract [en]

    An overview of the strategy and experimental solid-state NMR, STEM, and AFM methods useful for obtaining structural constraints on Alzheimer’s amyloid-β peptide fibrils is presented. Polymorphism of amyloid fibrils and the relevance to neurotoxicity is discussed.

  • 10.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Polymorphism of Alzheimer’s Aβ Amyloid Fibrils and Oligomers2018In: Modern Magnetic Resonance / [ed] Graham A. Webb, Cham: Springer, 2018, p. 333-347Chapter in book (Refereed)
    Abstract [en]

    An overview of the strategy and experimental solid-state NMR, TEM, STEM, and AFM methods useful for obtaining atomic-level-resolution structural models of Alzheimer’s amyloid-β peptide fibrils and oligomers is presented. Polymorphism of amyloid fibrils and oligomers and the relevance to neurotoxicity is discussed.

  • 11.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Polymorphism of Amyloid Fibrils and Aggregation Kinetics of Alzheimer's Abeta peptides: solid state NMR, EM and AFM studies2005In: NMR in Molecular Biology: EuroConference on Structural Genomics: Structure, Dynamics and Interactions of Biomolecules, 2005, p. 35-Conference paper (Refereed)
  • 12.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sideband manipulation in magic-angle-spinning nuclear magnetic resonance1999In: Progress in nuclear magnetic resonance spectroscopy, ISSN 0079-6565, E-ISSN 1873-3301, Vol. 35, no 3, p. 203-266Article in journal (Refereed)
  • 13.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Balbach, John J.
    Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda.
    Leapman, Richard D.
    Division of Bioengineering and Physical Science, Office of Research Services, National Institutes of Health, Bethesda.
    Rizzo, Nancy W.
    Division of Bioengineering and Physical Science, Office of Research Services, National Institutes of Health, Bethesda.
    Reed, Jennifer
    Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda.
    Tycko, Robert
    National Institutes of Health, Bethesda.
    Multiple quantum solid-state NMR indicates a parallel, not antiparallel, organization of β-sheets in Alzheimer's β-amyloid fibrils2000In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 97, no 24, p. 13045-13050Article in journal (Refereed)
    Abstract [en]

    Senile plaques associated with Alzheimer's disease contain deposits of fibrils formed by 39- to 43-residue β-amyloid peptides with possible neurotoxic effects. X-ray diffraction measurements on oriented fibril bundles have indicated an extended β-sheet structure for Alzheimer's β-amyloid fibrils and other amyloid fibrils, but the supramolecular organization of the β-sheets and other structural details are not well established because of the intrinsically noncrystalline, insoluble nature of amyloid fibrils. Here we report solid-state NMR measurements, using a multiple quantum (MQ) 13C NMR technique, that probe the β-sheet organization in fibrils formed by the full-length, 40-residue β-amyloid peptide (Aβ1-40). Although an antiparallel β-sheet organization often is assumed and is invoked in recent structural models for full-length β-amyloid fibrils, the MQNMR data indicate an in-register, parallel organization. This work provides site-specific, atomic-level structural constraints on full-length β-amyloid fibrils and applies MQNMR to a significant problem in structural biology.

  • 14.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Balbach, John J.
    National Institutes of Health.
    Tycko, Robert
    National Institutes of Health.
    Site-Specific Identification of Non-ß-Strand Conformations in Alzheimer's ß-Amyloid Fibrils by Solid-State NMR2003In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 84, no 5, p. 3326-3335Article in journal (Refereed)
    Abstract [en]

    The most well-established structural feature of amyloid fibrils is the cross-ß motif, an extended ß-sheet structure formed by ß-strands oriented perpendicular to the long fibril axis. Direct experimental identification of non-ß-strand conformations in amyloid fibrils has not been reported previously. Here we report the results of solid-state NMR measurements on amyloid fibrils formed by the 40-residue ß-amyloid peptide associated with Alzheimer's disease (Aß1-40), prepared synthetically with pairs of 13C labels at consecutive backbone carbonyl sites. The measurements probe the peptide backbone conformation in residues 24-30, a segment where a non-ß-strand conformation has been suggested by earlier sequence analysis, cross-linking experiments, and molecular modeling. Data obtained with the fpRFDR-CT, DQCSA, and 2D MAS exchange solid-state NMR techniques, which provide independent constraints on the and backbone torsion angles between the labeled carbonyl sites, indicate non-ß-strand conformations at G25, S26, and G29. These results represent the first site-specific identification and characterization of non-ß-strand peptide conformations in an amyloid fibril

  • 15. Antzutkin, Oleg
    et al.
    Benetis, N. P.
    Lindgren, M.
    Linköping University.
    Lund, A.
    Molecular motion of the Morpholin-1-yl radical in CF2 ClCFCl2 as studied by ESR: use of residual anisotrophy of powder spectra to extract dynamics1993In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 169, no 2, p. 195-205Article in journal (Refereed)
    Abstract [en]

    The dynamics of the deprotonated neutral morpholin-1-yl radical, trapped in a halocarbon matrix, CF2ClCFCl2, has been studied utilizing electron spin resonance (ESR) spectroscopy. The experimental lineshapes of the radical exhibit an alterating line-width effect in the temperature range 105-144 K. The major changes of the ESR lineshape were governed by the averaging of the nitrogen hyperfine anisotropy while no exchange of the isotropic hyperfine coupling constants was observed. Geometrical parameters specifying the restricted anisotropic rotation of the whole radical trapped in the matrix could be extracted. Two methods for simulating anisotropic exchange broadened ESR spectra, the secular and non-perturbative, were utilized to investigate the dynamics of the radical. A surprisingly simple ''three-site'' jump model with a barrier of almost-equal-to 3.6 kcal/mol can be applied in the simulation of the experimental spectra. It has been shown that the secular method cannot reproduce the exchange broadened ESR spectra of systems with large hyperfine anisotropy undergoing large internal reorganisation.

  • 16.
    Antzutkin, Oleg
    et al.
    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.
    Wong, Alan
    University of Warwick.
    Baldus, Johanna Becker
    University of Warwick.
    Hung, Ivan
    University of Warwick.
    Kukol, A.
    University of Warwick.
    Brown, Steven P.
    University of Warwick.
    Smith, Mark E.
    University of Warwick.
    Dupree, Ray
    University of Warwick.
    Exploring solid-state 17O NMR to distinguish secondary structures in Alzheimer's Aβ fibrils2009Conference paper (Refereed)
  • 17.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Filippov, Andrei
    Wong, Alan
    University of Warwick.
    Baldus, Johanna
    University of Warwick.
    Hung, Ivan
    University of Warwick.
    Kukol, A.
    University of Warwick.
    Brown, Steven P.
    University of Warwick.
    Smith, Mark E.
    University of Warwick.
    Dupree, Ray
    University of Warwick.
    Exploring solid-state 17O NMR to distinguish secondary structures in Alzheimer's Aβ fibrils2009In: Euromar 2009: Magnetics Resonance Conference, 5-9 July 2009, Göteborg, Sweden. Programme and Abstract Book, 2009, p. 107-Conference paper (Other academic)
    Abstract [en]

    It has been shown by a large number of studies that Alzheimer's disease (AD) amyloid-β-peptide (Aβ) deposits contribute directly to the disease's progressive neurodegeneration. Aggregation cascade for Aβ peptides, its relevance to neurotoxicity in the course of AD, various factors modulating Aβ aggregation kinetics and experimental methods useful for these studies were recently discussed [1]. Results of Tycko and co-workers point at neurotoxicity in vitro of the two different types of Alzheimer's amyloid fibrils dispersed by ultrasonication into small fragments [2]. The high toxicity of Aβ oligomers in vitro has been discussed by Stege et. al who have found that the molecular chaperone αB-crystallin prevents Aβ from forming amyloid fibrils but nevertheless enhances Aβ toxicity [3]. Glabe and co-workes successfully prepared antibodies for Aβ oligomers and small spherical aggregates using nanogold technology [4]. They also have shown that these antibodies decrease toxicity of Aβ for SH-SY5Y human neuroblastoma cell cultures in vitro [4]. In this concern both structure of Aβ-oligomers/fibrils and the specific  interaction (aggregation/fusion) of Aβ peptides with nerve cell membranes is of a particular importance [5].We explore Solid-State 17O NMR on selectively 17O,13C,15N-labeled Aβ(1-40), Aβ(11-25) and Ac-Aβ(16-22)-NH2 peptides to distinguish a parallel and anti-parallel β-sheet secondary structures in β-NH2 peptides to distinguish a parallel and anti-parallel β-sheet secondary structures in amyloid fibrils. Aβ(1-40) fibrils form in-registry parallel β-sheets [6], while Aβ(11-25) [7] and Ac-Aβ(16-22)-NH2 [8] form different anti-parallel β-sheet structures, which were previously identified β-NH2 [8] form different anti-parallel β-sheet structures, which were previously identified by 13C multiple-quantum and 13C{15N} REDOR solid-state NMR. In our unpublished work presented here it was found that 17O NMR chemical shifts are sensitive to the type of the secondary structure, i. e. a parallel vs. an anti-parallel β-sheet structures, while the quadrupolar parameters of 17O nuclei unexpectedly do not vary beyond the error limits in the simulated lineshapes of both fibrillized and unfibrillized peptide systems. Results of more advanced solidstate NMR techniques to measure heteronuclear distances, 15N{17O}-REAPDOR, 15N{17O}-TRAPDOR and 17O{15N}-REDOR on selectively 17O-Val18 and 15N-Phe20 labeled Ac-Aβ(16-22)-NH2 fibrils will be also discussed. These novel solid-state NMR experiments will provide additional tools for measuring hydrogen bonding in different secondary structures of peptides in amyloid fibrils.[1.] O.N.Antzutkin, Magn. Reson. Chem. 42 (2004) 231-246; [2.] A.Petkova et al. Science 307 (2005) 262-265; [3.] G.J.J.Stege, et al. Biochem. Biophys. Res. Comm., 262 (1999) 152-156;[4.] R.Kayed et al. Science, 300 (2003) 486-489; [5.] M.Bokvist, et al. J. Mol. Biol. 335 (2004) 1039-1049; [6.] O.N. Antzutkin, et al. Proc. Nat. Acad. Sci, U.S.A., 97 (2000) 13045-13050;[7.] A.T. Petkova, et al. J. Mol. Biol., 335 (2004) 247-260;[8.] J.J. Balbach, Y. (2000) 13045-13050; [9] A.T. Petkova, (2004) 247-260; [10] J.J. Balbach, Y.Ishii, O.N. Antzutkin, et al. Biochemistry 39 (2000) 13748-13759.

  • 18.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Iuga, Dino
    Department of Physics, Warwick University, Coventry.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kelly, Robert T.
    Department of Physics, Warwick University, Coventry.
    Becker-Baldus, Johanna
    Department of Physics, Warwick University, Coventry.
    Brown, Steven P.
    Department of Physics, Warwick University, Coventry.
    Dupree, Ray
    Department of Physics, Warwick University, Coventry.
    Hydrogen bonding in Alzheimer’s amyloid-β fibrils probed by 15N{17O} REAPDOR solid-state NMR spectroscopy2012In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 51, no 41, p. 10289-10292Article in journal (Refereed)
    Abstract [en]

    An exclusive label: 15N{17O} REAPDOR NMR was used to validate intermolecular C17O⋅⋅⋅H15N hydrogen bonding in Ac-Aβ(16–22)-NH2 (see scheme) and Aβ(11–25) amyloid fibrils, which are associated with Alzheimer’s disease, by selectively labeling them with 17O and 15N. This method was effective for confirming the structure of these fibrils, and could be useful for a number of other biological samples.

  • 19.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Iuga, Dinu
    Department of Physics, Warwick University, Coventry.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kelly, Robert T.
    Department of Physics, Warwick University, Coventry.
    Becker-Baldus, Johanna
    Department of Physics, Warwick University, Coventry.
    Brown, Steven P.
    Department of Physics, Warwick University, Coventry.
    Dupree, Ray
    Department of Physics, Warwick University, Coventry.
    Hydrogen bonding in Alzheimer’s amyloid-β fibrils probed by 15N{17O} REAPDOR solid-state NMR spectroscopy2012In: Angewandte Chemie, ISSN 0044-8249, Vol. 124, no 41, p. 10435-10438Article in journal (Refereed)
    Abstract [en]

    Nach selektiver Markierung mit 17O und 15N wurden mithilfe von 15N{17O}-REAPDOR-NMR-Spektroskopie intermolekulare C17O⋅⋅⋅H15N-Wasserstoffbrücken in Ac-Aβ(16–22)-NH2- (siehe Schema) und Aβ(11–25)-Amyloidfibrillen untersucht, die mit der Alzheimer-Krankheit in Verbindung gebracht werden. Die Methode, die eine Bestätigung für die Struktur dieser Fibrillen lieferte, könnte auch im Zusammenhang mit anderen biologischen Proben nützlich sein.

  • 20.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ikumapayi, Fatai
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gunneriusson, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Johansson, Björn
    New Boliden AB.
    Berggren, Andreas
    New Boliden AB.
    Larsson, Anna-Carin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Bhuiyan, Iftekhar Uddin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsmo, Seija
    LKAB.
    Interactions in multi-component mineral systems2011Conference paper (Other academic)
  • 21.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ikumapayi, Fatai
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Johansson, Björn
    New Boliden AB.
    Berggren, Andreas
    New Boliden AB.
    Larsson, Anna-Carin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Holmgren, Allan
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mouzon, Johanne
    Bhuiyan, Iftekhar Uddin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsmo, Seija
    LKAB.
    Interactions in multi-component mineral systems2010Conference paper (Other academic)
  • 22.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Leapman, Richard D.
    Division of Physical Science, Office of Research Services, National Institutes of Health, Bethesda.
    Balbach, John J.
    Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda.
    Tycko, Robert
    Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda.
    Supramolecular structural constraints on Alzheimer's β-amyloid fibrils from electron microscopy and solid-state nuclear magnetic resonance2002In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 41, no 51, p. 15436-15450Article in journal (Refereed)
    Abstract [en]

    We describe electron microscopy (EM), scanning transmission electron microscopy (STEM), and solid-state nuclear magnetic resonance (NMR) measurements on amyloid fibrils formed by the 42-residue β-amyloid peptide associated with Alzheimer's disease (Aβ1-42) and by residues 10-35 of the full-length peptide (Aβ10-35). These measurements place constraints on the supramolecular structure of the amyloid fibrils, especially the type of β-sheets present in the characteristic amyloid cross-β structural motif and the assembly of these β-sheets into a fibril. EM images of negatively stained Aβ10-35 fibrils and measurements of fibril mass per length (MPL) by STEM show a strong dependence of fibril morphology and MPL on pH. Aβ10-35 fibrils formed at pH 3.7 are single "protofilaments" with MPL equal to twice the value expected for a single cross-β layer. Aβ10-35 fibrils formed at pH 7.4 are apparently pairs of protofilaments or higher order bundles. EM and STEM data for Aβ1-42 fibrils indicate that protofilaments with MPL equal to twice the value expected for a single cross-β layer are also formed by Aβ1-42 and that these protofilaments exist singly and in pairs at pH 7.4. Solid-state NMR measurements of intermolecular distances in Aβ10-35 fibrils, using multiple-quantum 13C NMR, 13C-13C dipolar recoupling, and 15N-13C dipolar recoupling techniques, support the in-register parallel β-sheet organization previously established by Lynn, Meredith, Botto, and co-workers [Benzinger et al. (1998) Proc. Natl. Acad. Sci. U.S.A. 95, 13407-13412; Benzinger et al. (2000) Biochemistry 39, 3491-3499] and show that this β-sheet organization is present at pH 3.7 as well as pH 7.4 despite the differences in fibril morphology and MPL. Solid-state NMR measurements of intermolecular distances in Aβ1-42 fibrils, which represent the first NMR data on Aβ1-42 fibrils, also indicate an in-register parallel β-sheet organization. These results, along with previously reported data on Aβ1-40 fibrils, suggest that the supramolecular structures of Aβ10-35, Aβ1-40, and Aβ1-42 fibrils are quite similar. A schematic structural model of these fibrils, consistent with known experimental EM, STEM, and solid-state NMR data, is presented

  • 23.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Lee, Young K.
    Stockholm University.
    Levitt, Malcolm H.
    Stockholm University.
    13C and15N-chemical shift anisotropy of ampicillin and penicillin-V studied by 2D-PASS and CP/MAS NMR1998In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 135, no 1, p. 144-155Article in journal (Refereed)
    Abstract [en]

    The principal values of the chemical shift tensors of all13C and15N sites in two antibiotics, ampicillin and penicillin-V, were determined by 2-dimensionalphaseadjustedspinningsideband (2D-PASS) and conventional CP/MAS experiments. The13C and15N chemical shift anisotropies (CSA), and their confidence limits, were evaluated using a Mathematica program. The CSA values suggest a revised assignment of the 2-methyl13C sites in the case of ampicillin. We speculate on a relationship between the chemical shift principal values of many of the13C and15N sites and the β-lactam ring conformation

  • 24. Antzutkin, Oleg
    et al.
    Levitt, Malcolm H.
    Stockholm University.
    Centerband phase shift in the TOSS spectra of a magic-angle-spinning single crystal1996In: Journal of Magnetic Resonance - Series A, ISSN 1064-1858, E-ISSN 1096-0864, Vol. 118, no 2, p. 295-298Article in journal (Refereed)
  • 25.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Levitt, Malcolm H.
    Stockholm University.
    Coherence transfer signals in the rotational resonance NMR of a spinning single crystal2000In: Journal of magnetic resonance, ISSN 1090-7807, E-ISSN 1096-0856, Vol. 147, no 1, p. 147-151Article in journal (Refereed)
    Abstract [en]

    A recent analysis of rotational resonance lineshapes (M. Helmle et al., J. Magn. Reson. 140, 379-403, 1999) predicted the existence of coherence transfer signals, which are generated by mechanically induced coherence transfer during the detection process. These signals correspond to the generation of observable coherences at spin sites that have no magnetization at the beginning of the observation interval but which acquire coherence while the detection is underway. The coherence transfer signals disappear for powder samples in conventional magic-angle-spinning solid-state NMR experiments. In this Communication, we report the successful detection of coherence transfer signals in rotor-synchronized experiments performed on a single crystal of [1,2-13C2]glycine.

  • 26. Antzutkin, Oleg
    et al.
    Lindgren, M.
    Linköping University.
    Koptyug, A. V.
    Lund, A.
    Optically dectected ESR (OD-ESR) of iron-radical pairs in colored solutions: observation of transient trans-Azobenzene radical cation1993In: Applied Magnetic Resonance, ISSN 0937-9347, E-ISSN 1613-7507, Vol. 5, no 1, p. 77-86Article in journal (Refereed)
    Abstract [en]

    Trans-azobenzene dissolved in different liquid hydrocarbons absorbs fluorescence arising from all acceptors previously used in Fluorescence Detected Magnetic Resonance (FDMR) and Optically Detected ESR (OD ESR) spectroscopy making optical detection impossible. In this report a new acceptor, rubrene, having sufficient quantum yield of fluorescence in the red band 550-620 nm, has been proven successful. OD ESR spectra of the radical-ion pair trans-azobenzene+/rubrene- were detected in liquid squalane (2,6,10,15,19,23-hexamethyl-tetracosane) solution in the temperature range 294-243 K. The experimental isotropic hyperfine splittings of the radical cation of trans-azobenzene (a(N) = 1.4 mT) have been compared with those from MNDO/INDO calculations and with those of earlier work using freon matrix studies.

  • 27. Antzutkin, Oleg
    et al.
    Lindgren, M.
    Linköping University.
    Lund, A.
    Sjöqvist, L.
    Observation of Piperidine aggregation and of Hydrogen-proton transfer between Piperidine radical cations and Piperidine molecules in Freon matrice: an E.S.R. study at cryogenic temperaturs1992In: Journal of the Chemical Society. Chemical communications, ISSN 0022-4936, no 21, p. 1547-1550Article in journal (Refereed)
    Abstract [en]

    Piperidine forms small aggregates in most Freon matrices at cryogenic temperatures; upon X-irradiation, hydrogen-proton transfer between piperidine radical cations and piperidine molecules occurs.

  • 28.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Norlin, N.
    Hellberg, M.
    Eriksson, P.
    Almqvist, Nils
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Leapman, R.D.
    Tycko, R.
    Petkova, A.T.
    Toth, I.
    Howes, A.P.
    Dupree, R.
    Binding of Aluminium(III)-Citrate Complexes, [Al3(H-1Cit)3(OH)]-4 and [Al3(H-1Cit)3(OH)4]-7, to Alzheimer's A-beta(1-40) Peptides: In situ Atomic Force, Electron Microscopy and Solid State 13C and 27Al NMR Studies2005In: Sixth Keele Meeting on Aluminium: Aluminium Lithosphere to Biosphere (and Back), Centro de Estudos do Ambiente e Mar, Universidade de Aveiro , 2005, p. 16-Conference paper (Other academic)
    Abstract [en]

    It is believed that Alzheimer's disease (AD) amyloid-β-peptide (Aβ) deposits contribute directly to the disease's progressive neurodegeneration. Aggregation cascade for Aβ peptides, its relevance to neurotoxicity in the course of AD, various factors modulating Aβ aggregation kinetics and experimental methods useful for these studies were recently discussed [1]. Al(III), Zn(II), Cu(II) and Fe(III) ions are often colocalized at the center of the core of Alzheimer's amyloid plaques [2] and are suggested to promote aggregation of physiological concentrations of Aβ [3]. It has also been suggested that Al can block calcium permeable putative Aβ-peptide channels in bilayer membranes [4]. Therefore studies of complexation of metal ions with Aβ-oligomers and fibrils are important in the search for the causes of and potential treatments for AD.We studied effects of highly soluble and biologically relevant aluminium(III)-citrate compounds, [Al3(H-1Cit)3(OH)]-4 and [Al3(H-1Cit)3(OH)4]-7, on the fibrillogenesis of Aβ(1-40). All resonances in 156.37 MHz 27Al and 90.52 MHz 13C MAS NMR spectra of powder Al(III)-citrate complexes were assigned. 27Al MAS NMR of dialysed samples of Aβ(1-40) co-incubated with the Al(III)-citrate complexes at different concentrations in TRIS buffer solutions, pH 7.4, shows that Al(III)-citrates bind to Aβ(1-40) as [Al3(H-1Cit)3(OH)]-4 and either accelerate ([Al3(H-1Cit)3(OH)]-4 complex) or retard ([Al3(H-1Cit)3(OH)4]-7 compound) aggregation of Aβ(1-40) as revealed by AFM. [1] ON Antzutkin, Magn. Reson. Chem. 42 (2004) 231; [2] MA Lovell et al., J. Neurol. Sci. 158 (1998) 47; Ch Exley et al., Al and Alzheimer's disease, Ch Exley (Ed)1998) 47; Ch Exley , Ch Exley (Ed) Elsevier Science, 2001, 421; [3] PW Mantyh et al., J. Neurochem. 61 (1993) 1171; [4] N Arispe et al, PNAS 90 (1993) 567.

  • 29.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Glavatskikh, Sergei
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Högprestandasmörjmedel och tillsatser till smörjmedel för järnhaltiga och icke järnhaltiga materialPatent (Other (popular science, discussion, etc.))
  • 30. Antzutkin, Oleg
    et al.
    Shekar, S.C.
    Stockholm University.
    Levitt, M.H.
    Stockholm University.
    2-dimensional side-band separation in magic-angle-spinning NMR1995In: Journal of Magnetic Resonance - Series A, ISSN 1064-1858, E-ISSN 1096-0864, Vol. 115, no 1, p. 7-19Article in journal (Refereed)
    Abstract [en]

    A new method for separating isotropic and anisotropic chemical-shift interactions in magic-angle-spinning NMR is presented. The new method is based upon manipulation of the phases of spinning sidebands using sequences of five π pulses. A two-dimensional pulse scheme separates the spinning sidebands by order. The amplitudes of the spinning sidebands may be analyzed to obtain the principal values of the chemical-shift anisotropy. For sites with many sidebands, it is possible to improve the signal-to-noise ratio considerably by skew projection of the two-dimensional spectrum. Experimental demonstrations are presented.

  • 31. Antzutkin, Oleg
    et al.
    Song, Zhiyang
    Stockholm University.
    Feng, Xiaolong
    Stockholm University.
    Levitt, Malcolm H.
    Stockholm University.
    Suppression of sidebands in magic-angle-spinning nuclear magnetic resonance: general principles and analytical solutions1994In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 100, no 1, p. 130-140Article in journal (Refereed)
    Abstract [en]

    Several theoretical and experimental aspects of sideband suppression in the nuclear magnetic resonance (NMR) spectra of rotating solids are considered. The principles of sideband suppression are explored using general symmetry arguments and previous treatments are examined critically. Analytical solutions are given for sideband suppression pulse sequences employing four, five, six, and nine pulses. The analytical solutions for four pulses are complete. Experimental demonstrations are given. The Journal of Chemical Physics is copyrighted by The American Institute of Physics.

  • 32.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Tycko, Robert
    National Institutes of Health.
    High-order multiple quantum excitation in 13C nuclear magnetic resonance spectroscopy of organic solids1999In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 110, no 6, p. 2749-2752Article in journal (Refereed)
    Abstract [en]

    Excitation and detection of high-order multiple quantum (MQ) coherences among 13C nuclear spins in singly-13C-labeled organic solids is demonstrated experimentally. MQ signals involving at least ten quanta of spin angular momentum are observed in nuclear magnetic resonance (NMR) measurements on polycrystalline L-methionine-methyl-13C and L-alanine-1-13C, using a time-reversible multiple pulse excitation sequence modified specifically for experiments on systems with weak homonuclear dipole-dipole couplings and strong inhomogeneous interactions such as anisotropic chemical shifts. The feasibility of high-order MQ excitation and detection in 13C-labeled organic solids promises to expand significantly the range of applications of MQ NMR as a structural tool, to include such systems as 13C-labeled synthetic polymers and biopolymers.

  • 33.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ullah Shah, Faiz
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Glavatskikh, Sergei
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Ionic-liquid-based lubricants and lubrication additives comprising ionsPatent (Other (popular science, discussion, etc.))
    Abstract [en]

    Anti-wear and friction-reducing lubricants and additives to lubricants for both ferrous and non-ferrous materials with/without DLC (diamiond-like-coatings) or graphene-based coatings, which are halogen free boron based ionic liqs. comprising a combination of an anion chosen from a mandelato borate anion, a salicylato borate anion, an oxalato borate anion, a malonato borate anion, a succinato borate anion, a glutarato borate anion and an adipato borate anion, with at least one cation selected from a tetraalkylphosphonium cation, a choline cation, an imidazolium cation and a pyrrolidinium cation, wherein said at least one cation has at least one alkyl group substituent with the general formula CnH2n+1 , wherein 1≤n≤80. Advantages of the invention include that it provides halogen free ionic liqs. for lubrication and that sensitivity for hydrolysis is reduced.

  • 34.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Velaga, Sitaram
    Luleå University of Technology, Department of Health Sciences, Medical Science.
    Wong, Alan
    Physics Department, University of Warwick, Coventry, UK CV4 7AL.
    Dupree, Ray
    Physics Department, University of Warwick, Coventry, UK CV4 7AL.
    Solid-state 17O, 13C and 15N NMR: from tackling structure of Alzheimer's Aβ fibrils to studies on anti-inflammatory drugs, Indomethacin-saccharin cocrystal2007Conference paper (Other academic)
  • 35.
    Appelblad, Petra
    et al.
    Luleå tekniska universitet.
    Baxter, Douglas
    Model for calculating dead time and mass discrimination correction factors from inductively coupled plasma mass spectrometry calibration curves2000In: Journal of Analytical Atomic Spectrometry, ISSN 0267-9477, E-ISSN 1364-5544, Vol. 15, no 5, p. 557-560Article in journal (Refereed)
    Abstract [en]

    A model allowing simultaneous determination of the detector dead time and the mass discrimination factor in inductively coupled plasma mass spectrometry (ICP-MS), as well as the corresponding uncertainties, is presented and compared for three representative isotope systems, namely magnesium, indium and thallium. The advantages of using the model presented are firstly that both the detector dead time and the mass discrimination factor can be obtained simultaneously and secondly that the sampling time can be spent entirely on the isotopes of interest.

  • 36.
    Appelblad, Petra K.
    Luleå tekniska universitet.
    Inductively coupled plasma mass spectrometry: fundamental studies2000Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Inductively coupled plasma mass spectrometry (ICP-MS) is in focus in this thesis. Fundamental studies of ICP double focusing magnetic sector MS are presented, and some possible applications are discussed. One of the recent innovations for increasing the sensitivity of ICP-MS is to use a Pt-shield inserted between the coil and the torch, which can be grounded. It is known that use of a shielded torch results in gain in sensitivity as well attenuation of the secondary discharge, but other physical parameters change as well. Thereby a thorough study of a torch with a Pt guard electrode has been performed in order to address these questions. Matrix effects from seawater samples are described. Isotope ratio measurements can be performed using ICP-MS. The raw data collected needs to be mathematically corrected for mass discrimination factors as well as detector dead time. A model is presented herein with which both these factors can be determined from calibration curves.

  • 37.
    Appelblad, Petra K.
    et al.
    Luleå tekniska universitet.
    Baxter, Douglas
    Thunberg, JO
    Determination of metal-humic complexes, free metal ions and total concentrations in natural waters1999In: Journal of Environmental Monitoring, ISSN 1464-0325, E-ISSN 1464-0333, Vol. 1, no 3, p. 211-7Article in journal (Refereed)
    Abstract [en]

    A comparison of two systems for the quantitation of metal-humic complexes and free metal ions, consisting of the separation by coupled ion exchange columns followed by detection by inductively coupled plasma mass spectrometry or cold vapour atomic fluorescence spectrometry, is presented. The systems evaluated comprised the serially coupled anion and cation exchangers, Sephadex A-25/Chelex 100 and Dowex 1X8/Chelamine Metalfix. Separation and preconcentration of the species studied were accomplished with both systems, elution being carried out using 2 M HNO3. Total concentrations, metal-humic complex fractions and free metal ion fractions of Al, Ba, Cd, Co, Cu, Fe, Hg, Mn, Pb, Sr, U and Zn in nine natural waters were determined. Statistical evaluation of the data from the two cation exchange materials, including results for additional elements, showed better precision (for Al, Ba, Cr, Cu and Mo) and higher recoveries (Al, Ba, Cd, Fe, Sr and Zn) for Chelex 100 than Chelamine Metalfix for free metal ions. On the other hand, Chelamine Metalfix recovered a significantly greater amount of Ni. The amounts of metal-humic complexes were compared with modelled distributions of these species, and one advantage of the preferred Sephadex A-25/Chelex 100 system is that the elements studied are all correctly classified with respect to their binding strengths to humic substances, which is not the case with the Dowex 1X8/Chelamine Metalfix pair. With the preferred system, metal-humic complexes can be reliably determined, as indicated by the results of equilibrium speciation modelling. However, comparison with the total concentrations showed statistically significant, non-quantitative recoveries of Al, Cu, Hg, Mn, U and Zn from some samples. Thus a combination of speciation and total concentration measurements is required to obtain a complete representation of the distribution of trace elements in natural waters.

  • 38. Appelblad, P.K.
    et al.
    Rodushkin, Ilia
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Baxter, Douglas
    Sources of uncertainty in isotope ratio measurements by inductively coupled plasma mass spectrometry2001In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 73, no 13, p. 2911-2919Article in journal (Refereed)
    Abstract [en]

    A model is presented describing the effects of dead time and mass bias correction factor uncertainties, flicker noise, and counting statistics on isotope ratio measurement precision using inductively coupled plasma mass spectrometry (ICPMS) with a single collector. Noise spectral analysis is exploited to enable estimation of the flicker noise parameters. For the instrument used, the flicker noise component exhibited a fairly weak frequency (f) dependence ( f -0.33±0.12), but was directly proportional to the total number of counts, Q. As white noise, determined by counting statistics, is given by Q0.5, the isotope ratio measurement uncertainties will actually cease to improve when Q exceeds a certain threshold. This would suggest that flicker noise could become the limiting factor for the precision with which isotope ratios can be determined by ICPMS. However, under most experimental conditions, uncertainties associated with mass discrimination and dead time correction factors are decisive. For ratios up to ~22 (115In/113In), optimum major isotope count rates are generally below 0.3 MHz, for which precision in the mass discrimination factor is limiting. The model derived could be used as a starting point for determining optimum conditions and understanding the limitations of single-collector ICPMS for precise isotope ratio measurements.

  • 39.
    Arkhipov, Victor P.
    et al.
    Kazan National Research Technological University.
    Bogdanova, Svetlana A.
    Kazan National Research Technological University.
    Idiyatullin, Zhamil Sh.
    Kazan National Research Technological University.
    Lunev, Ivan V.
    Institute of Physics, Kazan (Volga Region) Federal University.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Dynamic and structural properties of oxyethylated isononylphenols2016In: Mendeleev communications (Print), ISSN 0959-9436, E-ISSN 1364-551X, Vol. 26, no 4, p. 355-357Article in journal (Refereed)
    Abstract [en]

    Diffusion coefficients, dielectric relaxation times and refraction coefficients were measured, and activation energies of translational and rotational mobilities were determined for a series of oxyethylated phenols (neonols AF9-n) p-C9H19C6H4-O(CH2CH2O)nH, n = 4, 6, 8, 9, 10, 12, at different temperatures. The results demonstrated the existence of contraction and transition phenomena that changed the structure of neonol molecules at n ∼ 9 from a zigzag to a meander form.

  • 40.
    Arkhipov, Victor P.
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Department of Physics, Kazan National Research Technological 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.
    The cloud point of aqueous solutions of ethoxylated monoalkylphenols in the individual state and in the presence of electrolytes2018In: Journal of Dispersion Science and Technology, ISSN 0193-2691, E-ISSN 1532-2351, Vol. 39, no 10, p. 1442-1446Article in journal (Refereed)
    Abstract [en]

    The cloud points tcp of aqueous solutions of ethoxylated monoalkylphenols, AF9-n (n = 8,9,10,12), were measured in the concentration (C) range of 0.25-40 wt.%. tcp increased as C decreased at C < 1 wt.%. At 1 < С < 10 wt.%, tcp changed insignificantly; Δtcp/tcp did not exceed 5%. Solutions transformed into the gel state at С > 10-20 wt.% and tcp sharply increased. The dependence of tcp on the length of the oxyethylene chains of ethoxylated nonylphenols at C = 1 wt.% can be described by the equation tcp = b·ln(n-n0), where n0 = 6. The cloud points of aqueous solutions (C = 1 wt.%) of the ethoxylated nonylphenols were measured at different concentrations of NaI, NaCl, NaF, Na2CO3, and Na2SO4 salts. For all of these solutions, tcp decreased in the presence of NaCl, NaF, Na2CO3, Na2SO4 and increased in the presence of NaI. To describe the dependence of tcp on the salt concentration, the equation was suggested, where and tcp are the cloud points of a neat aqueous solution of ethoxylated nonylphenols and of the solution in the presence of electrolytes, respectively.

  • 41.
    Arkhipov, Victor P.
    et al.
    Kazan National Research Technological University.
    Idiyatullin, Zamil Sh.
    Kazan National Research Technological University.
    Gnezdilov, Oleg I.
    Institute of Physics, Kazan (Volga Region) Federal University.
    Petrova, Ekaterina V.
    Kazan National Research Technological University.
    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.
    Molecular self-diffusion and micellar structure in the aqueous solutions of AF9-10 ethoxylated isononylphenol near a cloud point2014In: Mendeleev communications (Print), ISSN 0959-9436, E-ISSN 1364-551X, Vol. 24, no 5, p. 266-268Article in journal (Refereed)
    Abstract [en]

    Sizes of micelles and compositions of aggregates in the aqueous solutions of the nonionic surfactant oxyethylated monoalkyl phenol (neonol AF9-10) were determined by NMR spectroscopy, NMR diffusometry and dynamic light scattering in a wide range of tem- peratures near the cloud point. The cloud point extraction of phenol from aqueous solutions by the surfactant AF9-10 was performed.

  • 42.
    Arkhipov, Victor P.
    et al.
    Kazan National Research Technological University.
    Idiyatullin, Zhamil Sh
    Kazan National Research Technological University.
    Potapova, Elisaveta
    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.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Micelles and aggregates of oxyethylated isononylphenols and their extraction properties near cloud point2014In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 118, no 20, p. 5480-5487Article in journal (Refereed)
    Abstract [en]

    We used nuclear magnetic resonance (NMR) spectroscopy and dynamic light scattering (DLS) techniques to study the structural and dynamic properties of micellar solutions of nonionic surfactants of a homologous series of oxyethylated isononylphenols - C9H19C6H 4O(C2H4O)nH, where n = 6, 8, 9, 10, or 12 - in a wide range of temperatures, including cloud points. The radii of the micelles and aggregates, as well as their compositions at different concentrations of surfactant, were determined. Using aqueous phenol solutions as a model, we studied the process of cloud point extraction with oxyethylated isononylphenols

  • 43.
    Arkhipov, Victor
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Potapova, Elisaveta
    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.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Micelle structure and molecular self-diffusion in isononylphenol ethoxylate–water systems2013In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 51, no 7, p. 424-430Article in journal (Refereed)
    Abstract [en]

    The structure and dynamic properties of micellar solutions of nonionic surfactants of a series of isononylphenol ethoxylates, C9H19C6H4O(C2H4O)nH (where n = 6,8,9,10, and 12), were studied by NMR diffusometry, dynamic light scattering, and viscosimetry. The sizes of the micelles were determined for different surfactants and at different surfactant concentrations. The numbers of water molecules bound by a micelle and by one oxyethylene group of the surfactant were estimated

  • 44.
    Balbach, John J.
    et al.
    National Institutes of Health.
    Ishii, Yoshitaka
    National Institutes of Health.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Leapman, Richard D.
    National Institutes of Health.
    Rizzo, Nancy W.
    National Institutes of Health.
    Dyda, Fred
    National Institutes of Health.
    Reed, Jennifer
    National Institutes of Health.
    Tycko, Robert
    University of California.
    Amyloid Fibril Formation by Aβ16-22, a Seven-Residue Fragment of the Alzheimer's β-Amyloid Peptide, and Structural Characterization by Solid State NMR2000In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 39, no 45, p. 13748-13759Article in journal (Refereed)
    Abstract [en]

    The seven-residue peptide N-acetyl-Lys-Leu-Val-Phe-Phe-Ala-Glu-NH2, called Aβ16-22 and representing residues 16-22 of the full-length β-amyloid peptide associated with Alzheimer's disease, is shown by electron microscopy to form highly ordered fibrils upon incubation of aqueous solutions. X-ray powder diffraction and optical birefringence measurements confirm that these are amyloid fibrils. The peptide conformation and supramolecular organization in Aβ16-22 fibrils are investigated by solid state 13C NMR measurements. Two-dimensional magic-angle spinning (2D MAS) exchange and constant-time double-quantum-filtered dipolar recoupling (CTDQFD) measurements indicate a β-strand conformation of the peptide backbone at the central phenylalanine. One-dimensional and two-dimensional spectra of selectively and uniformly labeled samples exhibit 13C NMR line widths of <2 ppm, demonstrating that the peptide, including amino acid side chains, has a well-ordered conformation in the fibrils. Two-dimensional 13C-13C chemical shift correlation spectroscopy permits a nearly complete assignment of backbone and side chain 13C NMR signals and indicates that the β-strand conformation extends across the entire hydrophobic segment from Leu17 through Ala21. 13C multiple-quantum (MQ) NMR and 13C/15N rotational echo double-resonance (REDOR) measurements indicate an antiparallel organization of β-sheets in the Aβ16-22 fibrils. These results suggest that the degree of structural order at the molecular level in amyloid fibrils can approach that in peptide or protein crystals, suggest how the supramolecular organization of β-sheets in amyloid fibrils can be dependent on the peptide sequence, and illustrate the utility of solid state NMR measurements as probes of the molecular structure of amyloid fibrils. Aβ16-22 is among the shortest fibril-forming fragments of full-length β-amyloid reported to date, and hence serves as a useful model system for physical studies of amyloid fibril formation.

  • 45.
    Balbach, John J.
    et al.
    National Institutes of Health.
    Petkova, Aneta T.
    National Institutes of Health.
    Oyler, Nathan A.
    National Institutes of Health.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gordon, David J.
    University of Chicago.
    Supramolecular structure in full-length Alzheimer's -amyloid fibrils: evidence for a parallel -sheet organization from solid-state nuclear magnetic resonance2002In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 83, no 2, p. 1205-1216Article in journal (Refereed)
  • 46. Baxter, Douglas
    et al.
    Rodushkin, Ilya
    ALS Scandinavia AB.
    Engström, Emma
    ALS Scandinavia AB.
    Isotope abundance ratio measurements by inductively coupled plasma-sector field mass spectrometry2012In: Journal of Analytical Atomic Spectrometry, ISSN 0267-9477, E-ISSN 1364-5544, Vol. 27, no 8, p. 1355-1381Article in journal (Refereed)
    Abstract [en]

    This tutorial reviews fundamental aspects of isotope abundance ratio measurement by inductively coupled plasma-sector field mass spectrometry (ICP-SFMS). After a synopsis of the scope of isotope abundance ratio measurement and a summary introduction to the factors affecting precision and accuracy, attention is turned to noise sources. Detailed theory behind Poisson or counting statistics and plasma flicker noise components is given, since much of the observed imprecision can be attributed to these sources. Using single collector instruments, ion beams from different isotopes are sampled in rapid sequence, and so ratioing of the signals will be subject to fluctuations derived from intensity variations, i.e., flicker noise. It is demonstrated that flicker noise can, under specified circumstances, become the limiting factor for the attainable precision. Furthermore, the practice of partitioning dwell times, ostensibly to optimize precision based on isotopic abundances and assumed Poisson statistics, is shown to be flawed and actually requires accounting for flicker noise. In addition to random uncertainty, various offset factors may contribute to systematic error in measured isotope abundance ratios. Two of these, namely mass scale shift and spectral interferences are ameliorated using ICP-SFMS. The former is eliminated when operating under conditions providing flat-topped peaks, such that the minor drift in mass calibration typical of the technique becomes inconsequential and the intensity remains the same. Isotope abundance ratio measurements are subject to three further important offset factors. First is abundance sensitivity, which quantifies the extent of peak tailing to neighboring masses and can present a considerable source of offset. Second is mass bias, resulting from the fact that all sector field devices exhibit increasing sensitivity with ion mass, and various empirical methods used to correct for this effect are compared and contrasted. Third is detector dead time, which affects mass spectrometers equipped with ion counting systems. Although a well-understood phenomenon, all current methods for determining the dead time on the basis of experimentally measured isotope abundance ratios are likely to yield biased estimates. Finally, the capabilities of ICP-SFMS for the determination of isotope abundance ratios are placed in perspective by making a brief comparison with other techniques.

  • 47.
    Beattie, D.A.
    et al.
    Ian Wark Research Institute, University of South Australia.
    Lidström-Larsson, Margareta
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    In situ total internal reflection Raman spectroscopy of surfactant adsorption at a mineral surface2006In: Vibrational Spectroscopy, ISSN 0924-2031, E-ISSN 1873-3697, Vol. 41, no 2, p. 198-204Article in journal (Refereed)
    Abstract [en]

    We present the first attempt to characterise surfactant adsorption from solution onto a particle film using total internal reflection Raman spectroscopy. Three surfactant collectors of interest to the mineral processing industry were studied in their adsorption onto sphalerite: heptyl xanthate, 2-mercaptobenzothiazole (MBT), and O,O-dibutyldithiophosphate (DTP). All three surfactants adsorbed to the surface of the sphalerite. Adsorption of heptyl xanthate was monitored as a function of time and increasing concentration. The spectrum of heptyl xanthate indicated the presence of a small amount of dixanthogen on the surface of the sphalerite. MBT adsorption studies were complicated due to the fluorescence of the adsorbed layer. However, peaks due to the adsorbed MBT were observed on top of the fluorescent background, allowing the identification of the adsorbed species to be confirmed as the oxidised dimer species. Spectra obtained from MBT and DTP co-adsorption studies did not display the strong adsorbate layer fluorescence, indicating that the fluorescence spectrum of the adsorbed MBT is most likely affected by ring-ring interactions.

  • 48.
    Becker-Baldus, Johanna
    et al.
    University of Warwick.
    Uldry, A-C
    Webber, A.L.
    Wong, Alan
    University of Warwick.
    Smith, Merk E.
    University of Warwick.
    Joyce, S.A.
    Yeats, J.R.
    Pickard, C.J.
    Dupree, Ray
    University of Warwick.
    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.
    Probing NH-O hydrogen bonding by solid-state NMR: using 15N-17O dipolar and J-couplings2009Conference paper (Refereed)
  • 49.
    Berezovsky, Vladimir
    et al.
    Department of Applied Mathematics and High-performance ComputingM.V.Lomonosov Northern (Arctic) Federal University, Arkhangelsk.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Computational study of the CO adsorption and diffusion in zeolites: validating the Reed–Ehrlich model2018In: Adsorption, ISSN 0929-5607, E-ISSN 1572-8757, Vol. 24, no 4, p. 403-413Article in journal (Refereed)
    Abstract [en]

    Molecular simulations have been employed to explore at the microscopic scale the adsorption of CO in zeolites (MFI, CHA and DDR). On the basis of classical force fields, grand canonical Monte Carlo simulations are performed to predict the adsorption properties (isotherms) of these types of zeolites up to high pressure. Subsequent careful analysis yields details the microscopic mechanism in play, along the whole adsorption process, together with a considering of the arrangements of CO in MFI at high pressure. This work also summarizes an approach which uses single component diffusion data in prediction of multicomponent diffusion.

  • 50.
    Bhaskar, Raju G.
    et al.
    Luleå tekniska universitet.
    Subrahmanyam, T.V
    Luleå tekniska universitet.
    Sun, Z.
    Luleå tekniska universitet.
    Forsling, Willis
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Shear-flocculation of quartz1991In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 32, no 3-4, p. 283-294Article in journal (Refereed)
    Abstract [en]

    The present work deals with the shear-flocculation of quartz in aqueous solutions of dodecylamine chloride. The variables studied include pH, concentration of the amine, size of the coarse particles, stirring speed and time. The zeta potentials were correlated with flocculation behaviour. It was observed that particle hydrophobicity and pH were most important since the dodecylamine chloride-solution reactions are pH-and concentration-dependent.

1234567 1 - 50 of 528
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