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  • 1.
    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.

  • 2.
    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)
  • 3.
    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.

  • 4.
    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.

  • 5.
    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.

  • 6.
    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)
  • 7.
    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)
  • 8.
    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.

  • 9.
    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

  • 10. 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.

  • 11.
    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)
  • 12.
    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.

  • 13.
    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.

  • 14.
    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.

  • 15.
    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)
  • 16.
    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)
  • 17.
    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

  • 18.
    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

  • 19. 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)
  • 20.
    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.

  • 21. 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.

  • 22. 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.

  • 23.
    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.

  • 24.
    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.))
  • 25. 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.

  • 26. 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.

  • 27.
    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.

  • 28.
    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.

  • 29.
    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)
  • 30.
    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.

  • 31.
    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

  • 32.
    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

  • 33.
    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.

  • 34.
    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)
  • 35.
    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)
  • 36.
    Blochin, Dimri S.
    et al.
    Institute of Physics, Kazan (Volga Region) Federal University.
    Aganova, Oksana V.
    Institute of Physics, Kazan (Volga Region) Federal University.
    Yulmetov, Aidar R.
    Institute of Physics, Kazan (Volga Region) Federal University.
    Filippov, Andrei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gizatulin, Bulat L.
    Institute of Physics, Kazan (Volga Region) Federal University.
    Afonin, Sergii
    Karlsruhe Institute of Technology.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Klochkov, Vladimir V.
    Institute of Physics, Kazan (Volga Region) Federal University.
    Spatial structure of heptapeptide Glu-Ile-Leu-Asn-His-Met-Lys, a fragment of the HIV enhancer prostatic acid phosphatase, in aqueous and SDS micelle solutions2013In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 1033, p. 59-66Article in journal (Refereed)
    Abstract [en]

    Prostatic acid phosphatase (PAP) is a protein abundantly present in human seminal fluid. PAP plays important role in fertilization. Its 39-amino-acid fragment, PAP(248-286), is effective in enhancing infectivity of HIV virus. In this work, we determined the spatial structure in aqueous solution of a heptapeptide within the PAP fragment, containing amino acid residues 266-272 (Glu-Ile-Leu-Asn-His-Met-Lys). We also report the structure of the complex formed by this heptapeptide with sodium dodecyl sulfate micelles, a model of a biological membrane, as determined by 1H NMR spectroscopy and 2D NMR (TOCSY, HSQC-HECADE, NOESY) spectroscopy. Complex formation was confirmed by chemical shift alterations in the 1H NMR spectra of the heptapeptide, as well as by the signs and values of NOE effects. We also present a comparison of the spatial structure of Glu-Ile-Leu-Asn-His-Met-Lys in water and in complex with sodium dodecyl sulfate

  • 37.
    Blokhin, Dimitry S.
    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.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Afonin, Sergei
    Karlsruhe Institute of Technology.
    Klochkov, Vladimir V.
    Institute of Physics, Kazan (Volga Region) Federal University.
    Spatial Structures of PAP(262–270) and PAP(274–284), Two Selected Fragments of PAP(248–286), an Enhancer of HIV Infectivity2015In: Applied Magnetic Resonance, ISSN 0937-9347, E-ISSN 1613-7507, Vol. 46, no 7, p. 757-769Article in journal (Refereed)
    Abstract [en]

    Prostatic acid phosphatase (PAP) assembles into amyloid fibrils that facilitate infection by HIV. Its peptide fragments PAP(248–286) and PAP(85–120) also enhance attachment of the virus by viral adhesion to the host cell prior to receptor-specific binding via reducing the electrostatic repulsion between the membranes of the virus and the target cell. The secondary structure of monomeric PAP(248–286) in a biomembrane-mimicking environment can be separated into an N-terminal unordered region, an α-helical central domain, and an α/310-helical C-terminal section (Nanga et al., J. Am. Chem. Soc., 131:17972–17979, 2009). In this work, we used two-dimensional nuclear magnetic resonance (2D NMR) spectroscopy techniques to study spatial structures of isolated central [PAP(262–270)] and C-terminal [PAP(274–284)] fragments of PAP(248–286) in SDS micelle solutions. NMR studies revealed the formation of complexes of both peptides with SDS micelles, with attraction to the micelle membranes occurring mainly through nonpolar and uncharged residues of the peptides. We demonstrate that, when interacting with SDS micelles, PAP(262–270) and PAP(274–284) form α-helical and 310-helical secondary structures, respectively, similar to that found previously for the 39-residue PAP(248–286).

  • 38.
    Blokhin, Dimitry S.
    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.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Karataeva, Farida Kh.
    Alexander Butlerov Institute of Chemistry, Kazan Federal University.
    Klochkov, Vladimir V.
    Institute of Physics, Kazan (Volga Region) Federal University.
    Spatial structure of oligopeptide PAP(248-261), the N-terminal fragment of the HIV enhancer prostatic acid phosphatase peptide PAP(248-286), in aqueous and SDS micelle solutions2014In: Journal of Molecular Structure, ISSN 0022-2860, E-ISSN 1872-8014, Vol. 1070, p. 38-42Article in journal (Refereed)
    Abstract [en]

    Prostatic acid phosphatase (PAP) is an enzyme that facilitates infection of cells by HIV. Its peptide fragment PAP(248-286) forms amyloid fibrils known as SEVI, which enhance attachment of the virus by viral adhesion to the host cell prior to receptor-specific binding via reducing the electrostatic repulsion between the membranes of the virus and the target cell. The secondary structure of PAP(248-286) in aqueous and SDS solutions can be divided into an N-terminal disordered region, an -helical central part and an /310-helical C-terminal region (R.P.R. Nanga et al., JACS, 2009, 131, 17972). In this work, we used NMR spectroscopy to study the spatial structure of the isolated N-terminal fragment of PAP(248-286), PAP(248-261) (GIHKQKEKSRLQGG), in aqueous and SDS micelle solutions. Formation of a PAP(248-261)-SDS complex was confirmed by chemical shift alterations in the 1H NMR spectra of the peptide, as well as by the signs and values of Nuclear Overhauser Effect (NOE). In addition, the PAP(248-261) peptide does not form any specified secondary structure in either aqueous or SDS solutions.

  • 39.
    Blokhin, D.S.
    et al.
    Institute of Physics, Kazan (Volga Region) Federal University.
    Efimov, S.V.
    Institute of Physics, Kazan (Volga Region) Federal University.
    Klochkov, A.V.
    Institute of Physics, Kazan (Volga Region) Federal University.
    Yulmetov, A.R.
    Institute of Physics, Kazan (Volga Region) Federal University.
    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.
    Aganov, A.G.
    Institute of Physics, Kazan (Volga Region) Federal University.
    Klochkov, V.V:
    Institute of Physics, Kazan (Volga Region) Federal University.
    Spatial structure of the decapeptide Val-Ile-Lys-Lys-Ser-Thr-Ala-Leu-Leu-Gly in water and in a complex with sodium dodecyl sulfate micelles2011In: Applied Magnetic Resonance, ISSN 0937-9347, E-ISSN 1613-7507, Vol. 41, no 2-4, p. 267-282Article in journal (Refereed)
    Abstract [en]

    We have studied the spatial structure of the decapeptide Val-Ile-Lys-Lys-Ser-Thr-Ala-Leu-Leu-Gly in aqueous solution and in a complex with sodium dodecyl sulfate (SDS) micelles by 1H nuclear magnetic resonance (NMR) spectroscopy and two-dimensional (2-D) NMR spectroscopy (total correlation spectroscopy and nuclear Overhauser effect spectroscopy (NOESY)). The approach used to determine the decapeptide spatial structure was based on analysis of the 1H–13C residual dipolar couplings in the molecules partially aligned in lyotropic liquid crystalline media. Analysis of the interproton distances obtained from the 2-D NOESY NMR spectrum was used to reveal the spatial structure of the decapeptide in a complex with SDS micelles. Complex formation was confirmed by analysis of 1H chemical shifts in the NMR spectrum of the decapeptide and analysis of the signs and values of NOEs in a solution with SDS micelles.

  • 40.
    Bradley, Jonathan P.
    et al.
    Department of Physics, Warwick University, Coventry.
    Velaga, Sitaram
    Luleå University of Technology, Department of Health Sciences, Medical Science.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Brown, Steven P.
    Department of Physics, Warwick University, Coventry.
    Probing intermolecular crystal packing in gamma-indomethacin by high-resolution 1H solid-state NMR spectroscopy2011In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 11, no 8, p. 3463-3471Article in journal (Refereed)
    Abstract [en]

    An NMR crystallography approach that combines experimental solid-state magic-angle-spinning (MAS) NMR with calculation is applied to the gamma polymorph of the pharmaceutical molecule, indomethacin. First-principles calculations (GIPAW) for the full crystal structure and an isolated molecule show changes in the (1)H chemical shift for specific aliphatic and aromatic protons of over -1 ppm that are due to intermolecular CH-pi interactions. For the OH proton, (1)H double-quantum (DQ) CRAMPS (combined rotation and multiple-pulse spectroscopy) spectra reveal intermolecular H-H proximities to the OH proton of the carboxylic acid dimer as well as to specific aromatic CH protons. The enhanced resolution in (1)H DQ-(13)C spectra, recorded at 850 MHz, enables separate (1)H DQ build-up curves (as a function of the DQ recoupling time) to be extracted for the aromatic CH protons. Supported by eight-spin density-matrix simulations, it is shown how the relative maximum intensities and rates of build-up provide quantitative insight into intramolecular and intermolecular H-H proximities that characterize the crystal packing

  • 41.
    Bredyuk, O. A.
    et al.
    Russian Adademy of Sciences.
    Gerasimenko, A. V.
    Russian Adademy of Sciences.
    Lutsenko, I. A.
    Russian Adademy of Sciences.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsling, Willis
    Structural organization of cadmium(II) and copper(II) dithiocarbamate complexes with dialkyl-substituted and cyclic ligands: Synthesis, single-crystal X-ray diffraction, EPR, and CP/MAS13C, 15N, and 113Cd NMR2005In: Russian Journal of Inorganic Chemistry, ISSN 0036-0236, E-ISSN 1531-8613, Vol. 50, no 11, p. 1710-1726Article in journal (Refereed)
    Abstract [en]

    A comparative study of polynuclear thallium complexes with dialkyldithiocarbamates [Tl2{S2CNR2} 2]n (R = CH3, i-C3H7, C4H9, and i-C4H9; R2 = (CH2)6) was performed by solid-state 13C and 15N CP/MAS NMR spectroscopy. The dithiocarbamate groups were found to be structurally equivalent in the complexes studied. An increase in the positive inductive effect of alkyl substituents at the N atom increased 15N chemical shifts as a result of a combination of positive inductive effect of the alkyl substituents and the mesomeric effect of =NC(S)S-groups. The first representative of thallium(I) complexes with a cyclic dithiocarbamate ligand [Tl2{S2CN(CH2) 6}2]n was obtained. Its molecular structure was determined from X-ray diffraction data. The β-form of the isotope-substituted complex [63/65CuTl2{S 2CN(CH2)6}4] was obtained and examined by EPR spectroscopy. The EPR spectra were modeled at the second order of the perturbation theory. The spin density at the thallium atoms was calculated and its distribution over the AOs of thallium was determined.

  • 42.
    Bredyuk, O.A.
    et al.
    Institute of Geology and Nature Management, Far East Branch, Russian Academy of Sciences.
    Loseva, Olga V.
    Institute of Geology and Nature Management, Far East Branch, Russian Academy of Sciences.
    Ivanov, Alexander V.
    Institute of Geology and Nature Management, Far Eastern Branch of the Russian Academy of Sciences .
    Gowda, Vasantha
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. University of Oulu.
    Antzutkin, Oleg N.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Warwick University, Coventry.
    Three-Dimensional Polymeric Thallium(I) Morpholinedithiocarbamate [Tl2{S2CN(CH2)4O}2]n and Its Capability of Binding Gold(III) from Solutions: Chemisorption Synthesis of a Heteronuclear Gold(III)–Thallium(III) Complex of the Ionic Type, ([Au{S2CN(CH2)4O}2][TlCl4])n, the Role of Secondary Interactions Tl…O, Tl…S, and Au…S in the Supramolecular Self-Organization, 13C MAS NMR, and Thermal Behavior2017In: Russian journal of coordination chemistry, ISSN 1070-3284, E-ISSN 1608-3318, Vol. 43, no 10, p. 638-651Article in journal (Refereed)
    Abstract [en]

    Crystalline polymeric thallium(I) morpholinedithiocarbamate [Tl2{S2CN(CH2)4O}2]n (I) and the heteronuclear ion–polymeric gold(III)–thalium(III) complex ([Au{S2CN(CH2)4O}2][TlCl4])n (II) are preparatively isolated and characterized by X-ray diffraction analysis and 13C MAS NMR spectroscopy. According to the X-ray diffraction data, the main structural units of compounds I and II (CIF files CCDC 1548079 and 1548080) are presented by the binuclear centrosymmetric molecule [Tl2{S2CN(CH2)4O}2], noncentrosymmetric complex cation [Au{S2CN(CH2)4O{2]+, and isomeric complex anions [TlCl4]. The formation of the three-dimensional polymeric structure (coordination number of Tl is 7), which is not characteristic of thallium(I) dithiocarbamates, is a consequence of the participation of the secondary Tl…O and Tl…S bonds of two types in the supramolecular self-organization of compound I. Nonequivalent secondary interactions of the first type join the binuclear molecules [Tl2{S2CN(CH2)4O}2] into polymer layers, which, in turn, form the three-dimensional polymeric framework due to the secondary bonds Tl…S. The revealed ability of freshly precipitated compound I to the chemisorption of gold(III) from solutions (2 M HCl) makes it possible to obtain heteronuclear supramolecular complex II as an individual form of binding. In the structure of the latter, the pairs of stronger secondary Au…S bonds join the gold(III) cations into dimers [Au2{S2CN(CH2)4O}4]2+ of the angular structure, the structural ordering of which is achieved in the cationcationic polymeric chain ([Au2{S2CN(CH2)4O}4]2+)n of the helical type involving the pairs of less strong Au…S bonds between the adjacent binuclear units. The distorted tetrahedral anions [TlCl4] are localized between the polymeric chains. The study of the thermal behavior of compounds I and II by simultaneous thermal analysis makes it possible to establish the character of thermal transformations of the substances and to identify Tl2S (I), TlCl, and elemental gold (II) as thermolysis products

  • 43.
    Dudenko, D.V.
    et al.
    Cardiff University.
    Williams, P.A.
    Cardiff University.
    Hughes, C.E.
    Cardiff University.
    Antzutkin, Oleg
    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.
    Brown, S.P.
    University of Warwick.
    Harris, K.D.M.
    Cardiff University.
    Exploiting the synergy of powder x-ray diffraction and solid-state NMR spectroscopy in structure determination of organic molecular solids2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 23, p. 12258-12265Article in journal (Refereed)
    Abstract [en]

    We report a strategy for structure determination of organic materials in which complete solid-state nuclear magnetic resonance (NMR) spectral data is utilized within the context of structure determination from powder X-ray diffraction (XRD) data. Following determination of the crystal structure from powder XRD data, first-principles density functional theory-based techniques within the GIPAW approach are exploited to calculate the solid-state NMR data for the structure, followed by careful scrutiny of the agreement with experimental solid-state NMR data. The successful application of this approach is demonstrated by structure determination of the 1:1 cocrystal of indomethacin and nicotinamide. The 1H and 13C chemical shifts calculated for the crystal structure determined from the powder XRD data are in excellent agreement with those measured experimentally, notably including the two-dimensional correlation of 1H and 13C chemical shifts for directly bonded 13C-1H moieties. The key feature of this combined approach is that the quality of the structure determined is assessed both against experimental powder XRD data and against experimental solid-state NMR data, thus providing a very robust validation of the veracity of the structure

  • 44.
    Emmerik, Tristan J. Van
    et al.
    La Trobe University.
    Sandström, Dan
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Angove, Michael J.
    La Trobe University.
    Johnson, Bruce B.
    La Trobe University.
    31P solid-state nuclear magnetic resonance study of the sorption of phosphate onto gibbsite and kaolinite2007In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, no 6, p. 3205-3213Article in journal (Refereed)
    Abstract [en]

    Sorption of phosphate onto gibbsite (Υ-Al(OH)3) and kaolinite has been studied by both macroscopic and 31P solid-state NMR measurements. Together these measurements indicate that phosphate is sorbed by a combination of surface complexation and surface precipitation with the relative amounts of these phases depending on pH and phosphate concentration. At low pH and high phosphate concentrations sorption is dominated by the presence of both amorphous and crystalline precipitate phases. The similarity between the single-pulse and CP/MAS NMR spectra suggests that the precipitate phases form a thin layer on the surface of the particles in close contact with protons from surface hydroxyl groups or coordinated water molecules. While the crystalline phase is only evident on samples below pH 7, amorphous AlPO4 was found at all pH and phosphate concentrations studied. As pH was increased the fraction of phosphate sorbed as an inner-sphere complex increased, becoming the dominant surface species by pH 8. Comparison of sorption and NMR results suggests that the inner-sphere complexes form by monodentate coordinat

  • 45.
    Farzaneh, Amirfarrokh
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Zhou, Ming
    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.
    Bacsik, Zoltan
    Department of Materials and Environmental Chemistry, Stockholm University.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Adsorption of Butanol and Water Vapors in Silicalite‑1 Films with a Low Defect Density2016In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, p. 11789-11798Article in journal (Refereed)
    Abstract [en]

    Pure silica zeolites are potentially hydrophobic and have therefore been considered to be interesting candidates for separating alcohols, e.g., 1-butanol, from water. Zeolites are traditionally synthesized at high pH, leading to the formation of intracrystalline defects in the form of silanol defects in the framework. These silanol groups introduce polar adsorption sites into the framework, potentially reducing the adsorption selectivity toward alcohols in alcohol/water mixtures. In contrast, zeolites prepared at neutral pH using the fluoride route contain significantly fewer defects. Such crystals should show a much higher butanol/water selectivity than crystals prepared in traditional hydroxide (OH−) media. Moreover, silanol groups are present at the external surface of the zeolite crystals; therefore, minimizing the external surface of the studied adsorbent is important. In this work, we determine adsorption isotherms of 1-butanol and water in silicalite-1 films prepared in a fluoride (F−) medium using in situ attenuated total reflectance−Fourier transform infrared (ATR−FTIR) spectroscopy. This film was composed of well intergrown, plate-shaped b-oriented crystals, resulting in a low external area. Single-component adsorption isotherms of 1-butanol and water were determined in the temperature range of 35− 80 °C. The 1-butanol isotherms were typical for an adsorbate showing a high affinity for a microporous material and a large increase in the amount adsorbed at low partial pressures of 1-butanol. The Langmuir−Freundlich model was successfully fitted to the 1-butanol isotherms, and the heat of adsorption was determined. Water showed a very low affinity for the adsorbent, and the amounts adsorbed were very similar to previous reports for large silicalite-1 crystals prepared in a fluoride medium. The sample also adsorbed much less water than did a reference silicalite-1(OH−) film containing a high density of internal defects.The results show that silicalite-1 films prepared in a F− medium with a low density of defects and external area are very promising for the selective recovery of 1-butanol from aqueous solutions.

  • 46.
    Felippov, A.
    et al.
    Umeå university.
    Sulejmanova, A.
    Kazan State University, Tatarstan.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Grobner, G.
    Umeå university.
    Diffusion and aggregation of Alzheimer's Aβ1-40 peptide in aqueous trifluoroethanol solutions as studied by pulsed field gradient NMR2005In: Applied Magnetic Resonance, ISSN 0937-9347, E-ISSN 1613-7507, Vol. 29, no 3, p. 439-449Article in journal (Refereed)
    Abstract [en]

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

  • 47.
    Feng, X.
    et al.
    Stockholms Universitet.
    Edén, M.
    Stockholms Universitet.
    Brinkmann, A.
    Stockholms Universitet.
    Luthman, H.
    Eriksson, L.
    Gräslund, A.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Levitt, M.H.
    Direct determination of a peptide torsional angle Ψ by double-quantum solid-state NMR1997In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 119, p. 12006-12007Article in journal (Other academic)
  • 48.
    Filippov, A. V.
    et al.
    Kazan State University, Tatarstan.
    Suleimanova, A. V.
    Kazan State University, Tatarstan.
    Grobner, G.
    Umea University, Department of Chemistry.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Effect of freezing on amyloid peptide aggregation and self-diffusion in an aqueous solution2008In: Colloid Journal of the Russian Academy of Science, ISSN 1061-933X, E-ISSN 1608-3067, Vol. 70, no 4, p. 501-506Article in journal (Refereed)
    Abstract [en]

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

  • 49.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Influence of Alzheimer´s beta-amyloid peptide on the lateral diffusion of lipids in raft-forming bilayers2013In: Mendeleev communications (Print), ISSN 0959-9436, E-ISSN 1364-551X, Vol. 23, no 6, p. 316-318Article in journal (Refereed)
    Abstract [en]

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

  • 50.
    Filippov, Andrei
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Institute of Physics, Kazan Federal University, Kazan, Russia .
    Antzutkin, Oleg N.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Department of Physics, Warwick University, Coventry, United Kingdom .
    Magnetic field effects dynamics of ethylammonium nitrate ionic liquid confined between glass plates2018In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 9, p. 6316-6320Article in journal (Refereed)
    Abstract [en]

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

12345 1 - 50 of 215
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