Laboratory of biomolecular NMR-spectroscopy

Department of structural biology

Head: Alexander Arseniev, D. Sc., professor
+7 (495) 330-59-29 · aars@nmr.ru

www.nmr.ru

NMR spectroscopy, membrane and membrane-active peptides and proteins, ion channels, G-protein conjugate receptors, helix-coil interaction medium, membrane-modeling medium

Laboratory investigates the structure of proteins and peptides. For this purpose Laboratory uses one of the most powerful modern techniques – nuclear magnetic resonance spectroscopy (NMR).

The research of the Laboratory is focused on the membrane proteins such as receptor tyrosine kinases, ion channels, toll-like receptors, the beta-amyloid precursor protein, GPCR-s and others. The properties of natural luciferins, the blockers of pain receptors, the viral proteins required for the infection s, as well as the mechanisms of ligand-receptor interactions are also under investigation.

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Most of the research is directly related to practical issues such as the search for anti-cancer targets, the causes of Alzheimer's disease, the creation of effective painkillers, specific diagnostic systems and others.

At the disposal of the Laboratory are the most advanced devices of the Bruker company: 600, 700 and 800 MHz machines, equipped with the supersensitive cryogenic probes, and a solid-state MAS probe. In addition, the Laboratory has necessary equipment and techniques for bacterial in-cell and cell-free synthesis ofrecombinant proteins and their physicochemical characterization. Methods for the production of isotropicaly and selectively isotope-labeled proteins were developed on their basis.

All aforesaid allows us to successfully solve the most difficult tasks within and beyond the capabilities of modern structural biology.

Laboratory equipment is a part of the IBCh Shared Research Center, so it is possible to analyze the samples of high complexity by NMR spectroscopy on a commercial basis.

The Laboratory has a rich history. In 1965 it was founded by Vladimir F. Bystrov, the associate member of the USSR Academy of Sciences. He was one of the first in the world who began to engage in structural studies of proteins and peptides in solution by NMR spectroscopy and created the largest in the Soviet Union scientific school. In 1990 the laboratory was headed by his apprentice, Professor Alexander Arseniev.

The Laboratory continues to develop the Bystrov’s initiatives till now and is considered as the one of the leading schools in the world of NMR. Each year it produces new highly qualified professionals and PhDs who can solve the most complex problems using NMR-spectroscopy.

Nowadays Laboratory has many friends and partners. Among them are the laboratory of Nobel laureate Kurt Wüthrich, one of the strongest NMR-laboratory in the world of Professor Gerhard Wagner, "Novartis", the second-largest pharmaceutical company in the world and others.

Today, our lab is a very friendly team which has set itself the most ambitious goals and is ready for any interesting collaboration!

 

NamePositionE-mail
Eduard V. Bocharov, ph. d.s. r. f.
Olga V. Bocharova, ph. d.s. r. f.
Pavel E. BraginPhD stud.
Vladimir V. Chupin, d. sc., professorl. r. f.
Maxim A. Dubinnyi, ph. d.r. f.
Marina V. Goncharuk, ph. d.r. f.
Sergey A. Goncharuk, ph. d.r. f.
Dmitry M. Lesovoy, ph. d.r. f.
Konstantin S. Mineev, ph. d.r. f.
Mikhail Y. Myshkinres. eng.
Kirill D. Nadezhdin, ph. d.r. f.
Svetlana B. Nol'dej. r. f.
Alexander S. Paramonov, ph. d.r. f.
Zakhar O. Shenkarev, ph. d.s. r. f.
Anatolii S. UrbanPhD stud.

Selected publications

  1. Melnikova D.N., Mineev K.S., Finkina E.I., Arseniev A.S., Ovchinnikova T.V. (2016). A novel lipid transfer protein from the dill Anethum graveolens L.: isolation, structure, heterologous expression, and functional characteristics. J. Pept. Sci. 22 (1), 59–66 [+]

    A novel lipid transfer protein, designated as Ag-LTP, was isolated from aerial parts of the dill Anethum graveolens L. Structural, antimicrobial, and lipid binding properties of the protein were studied. Complete amino acid sequence of Ag-LTP was determined. The protein has molecular mass of 9524.4 Da, consists of 93 amino acid residues including eight cysteines forming four disulfide bonds. The recombinant Ag-LTP was overexpressed in Escherichia coli and purified. NMR investigation shows that the Ag-LTP spatial structure contains four α-helices, forming the internal hydrophobic cavity, and a long C-terminal tail. The measured volume of the Ag-LTP hydrophobic cavity is equal to ~800 A(3) , which is much larger than those of other plant LTP1s. Ag-LTP has weak antifungal activity and unpronounced lipid binding specificity but effectively binds plant hormone jasmonic acid. Our results afford further molecular insight into biological functions of LTP in plants. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd.

    ID:1370
  2. Lyukmanova E.N., Shenkarev Z.O., Shulepko M.A., Paramonov A.S., Chugunov A.O., Janickova H., Dolejsi E., Dolezal V., Utkin Y.N., Tsetlin V.I., Arseniev A.S., Efremov R.G., Dolgikh D.A., Kirpichnikov M.P. (2015). Structural Insight into Specificity of Interactions between Nonconventional Three-finger Weak Toxin from Naja kaouthia (WTX) and Muscarinic Acetylcholine Receptors. J. Biol. Chem. 290 (39), 23616–30 [+]

    Weak toxin from Naja kaouthia (WTX) belongs to the group of nonconventional "three-finger" snake neurotoxins. It irreversibly inhibits nicotinic acetylcholine receptors and allosterically interacts with muscarinic acetylcholine receptors (mAChRs). Using site-directed mutagenesis, NMR spectroscopy, and computer modeling, we investigated the recombinant mutant WTX analogue (rWTX) which, compared with the native toxin, has an additional N-terminal methionine residue. In comparison with the wild-type toxin, rWTX demonstrated an altered pharmacological profile, decreased binding of orthosteric antagonist N-methylscopolamine to human M1- and M2-mAChRs, and increased antagonist binding to M3-mAChR. Positively charged arginine residues located in the flexible loop II were found to be crucial for rWTX interactions with all types of mAChR. Computer modeling suggested that the rWTX loop II protrudes to the M1-mAChR allosteric ligand-binding site blocking the entrance to the orthosteric site. In contrast, toxin interacts with M3-mAChR by loop II without penetration into the allosteric site. Data obtained provide new structural insight into the target-specific allosteric regulation of mAChRs by "three-finger" snake neurotoxins.

    ID:1394
  3. Mineev K.S., Goncharuk S.A., Kuzmichev P.K., Vilar M., Arseniev A.S. (2015). NMR Dynamics of Transmembrane and Intracellular Domains of p75NTR in Lipid-Protein Nanodiscs. Biophys. J. 109 (4), 772–82 [+]

    P75NTR is a type I integral membrane protein that plays a key role in neurotrophin signaling. However, structural data for the receptor in various functional states are sparse and controversial. In this work, we studied the spatial structure and mobility of the transmembrane and intracellular parts of p75NTR, incorporated into lipid-protein nanodiscs of various sizes and compositions, by solution NMR spectroscopy. Our data reveal a high level of flexibility and disorder in the juxtamembrane chopper domain of p75NTR, which results in the motions of the receptor death domain being uncoupled from the motions of the transmembrane helix. Moreover, none of the intracellular domains of p75NTR demonstrated a propensity to interact with the membrane or to self-associate under the experimental conditions. The obtained data are discussed in the context of the receptor activation mechanism.

    ID:1312
  4. Berkut A.A., Peigneur S., Myshkin M.Y., Paramonov A.S., Lyukmanova E.N., Arseniev A.S., Grishin E.V., Tytgat J., Shenkarev Z.O., Vassilevski A.A. (2015). Structure of Membrane-active Toxin from Crab Spider Heriaeus melloteei Suggests Parallel Evolution of Sodium Channel Gating Modifiers in Araneomorphae and Mygalomorphae. J. Biol. Chem. 290 (1), 492–504 [+]

    We present a structural and functional study of a sodium channel activation inhibitor from crab spider venom. Hm-3 is an insecticidal peptide toxin consisting of 35 amino acid residues from the spider Heriaeus melloteei (Thomisidae). We produced Hm-3 recombinantly in Escherichia coli and determined its structure by NMR spectroscopy. Typical for spider toxins, Hm-3 was found to adopt the so-called "inhibitor cystine knot" or "knottin" fold stabilized by three disulfide bonds. Its molecule is amphiphilic with a hydrophobic ridge on the surface enriched in aromatic residues and surrounded by positive charges. Correspondingly, Hm-3 binds to both neutral and negatively charged lipid vesicles. Electrophysiological studies showed that at a concentration of 1 μm Hm-3 effectively inhibited a number of mammalian and insect sodium channels. Importantly, Hm-3 shifted the dependence of channel activation to more positive voltages. Moreover, the inhibition was voltage-dependent, and strong depolarizing prepulses attenuated Hm-3 activity. The toxin is therefore concluded to represent the first sodium channel gating modifier from an araneomorph spider and features a "membrane access" mechanism of action. Its amino acid sequence and position of the hydrophobic cluster are notably different from other known gating modifiers from spider venom, all of which are described from mygalomorph species. We hypothesize parallel evolution of inhibitor cystine knot toxins from Araneomorphae and Mygalomorphae suborders.

    ID:1138
  5. Dubovskii V., Vorontsova V., Utkin N., Arseniev S., Efremov G., Feofanov V. (2014). Cobra cytotoxins: determinants of antibacterial activity. Mendeleev Communications 25 (1), 70–71 [+]

    The investigation of antibacterial activity of three-finger cobra cytotoxins towards Gram-negative and Gram-positive bacteria showed no activity against the former species, whereas M. luteus was found most susceptible to cytotoxins. A correlation was revealed between this activity and hydrophobicity of the toxins (HTL scores), total charge and its distribution over the toxin molecule: the absence of Glu-16 residue and the presence of positively charged residues (Lys30/His31) in the tip of the loop 2.

    ID:1398
  6. Malakhov M.V., Dubinnyi M.A., Vlasova N.V., Zgoda V.G., Efremov R.G., Boldyrev I.A. (2014). End-group differentiating ozonolysis of furocoumarins. RSC Advances 4 (106), 61277–61280 [+]

    Ozonolysis of furocoumarins followed by reductive work-up yields not only common symmetrical dialdehydes, but also o-formylumbelliferones with moderate-to-high yields. Simultaneous formation of both products accounts for the transformation of carbonyl oxides – products of primary ozonide ring opening.

    ID:1097
  7. Mineev K.S., Goncharuk S.A., Arseniev A.S. (2014). Toll-like receptor 3 transmembrane domain is able to perform various homotypic interactions: An NMR structural study. FEBS Lett. , [+]

    Toll-like receptors (TLRs) take part in both the innate and adaptive immune systems. The role of the transmembrane domain in TLR signaling is still elusive, while its importance for the TLR activation was clearly demonstrated. In the present study the ability of the TLR3 transmembrane domain to form dimers and trimers in detergent micelles was shown by solution NMR spectroscopy. Spatial structures and free energy magnitudes were determined for the TLR3 transmembrane domain in dimeric and trimeric states, and two possible surfaces that may be used for the helix-helix interaction by the full-length TLR3 were revealed.

    ID:1107
  8. Manni S., Mineev K.S., Usmanova D., Lyukmanova E.N., Shulepko M.A., Kirpichnikov M.P., Winter J., Matkovic M., Deupi X., Arseniev A.S., BallmerHofer K. (2014). Structural and functional characterization of alternative transmembrane domain conformations in VEGF receptor 2 activation. Structure 22 (8), 1077–89 [+]

    Transmembrane signaling by receptor tyrosine kinases (RTKs) entails ligand-mediated dimerization and structural rearrangement of the extracellular domains. RTK activation also depends on the specific orientation of the transmembrane domain (TMD) helices, as suggested by pathogenic, constitutively active RTK mutants. Such mutant TMDs carry polar amino acids promoting stable transmembrane helix dimerization, which is essential for kinase activation. We investigated the effect of polar amino acids introduced into the TMD of vascular endothelial growth factor receptor 2, regulating blood vessel homeostasis. Two mutants showed constitutive kinase activity, suggesting that precise TMD orientation is mandatory for kinase activation. Nuclear magnetic resonance spectroscopy revealed that TMD helices in activated constructs were rotated by 180° relative to the interface of the wild-type conformation, confirming that ligand-mediated receptor activation indeed results from transmembrane helix rearrangement. A molecular dynamics simulation confirmed the transmembrane helix arrangement of wild-type and mutant TMDs revealed by nuclear magnetic resonance spectroscopy.

    ID:1104
  9. Sharonov G.V., Bocharov E.V., Kolosov P.M., Astapova M.V., Arseniev A.S., Feofanov A.V. (2014). Point mutations in dimerization motifs of the transmembrane domain stabilize active or inactive state of the EphA2 receptor tyrosine kinase. J. Biol. Chem. 289 (21), 14955–64 [+]

    The EphA2 receptor tyrosine kinase plays a central role in the regulation of cell adhesion and guidance in many human tissues. The activation of EphA2 occurs after proper dimerization/oligomerization in the plasma membrane, which occurs with the participation of extracellular and cytoplasmic domains. Our study revealed that the isolated transmembrane domain (TMD) of EphA2 embedded into the lipid bicelle dimerized via the heptad repeat motif L(535)X3G(539)X2A(542)X3V(546)X2L(549) rather than through the alternative glycine zipper motif A(536)X3G(540)X3G(544) (typical for TMD dimerization in many proteins). To evaluate the significance of TMD interactions for full-length EphA2, we substituted key residues in the heptad repeat motif (HR variant: G539I, A542I, G553I) or in the glycine zipper motif (GZ variant: G540I, G544I) and expressed YFP-tagged EphA2 (WT, HR, and GZ variants) in HEK293T cells. Confocal microscopy revealed a similar distribution of all EphA2-YFP variants in cells. The expression of EphA2-YFP variants and their kinase activity (phosphorylation of Tyr(588) and/or Tyr(594)) and ephrin-A3 binding were analyzed with flow cytometry on a single cell basis. Activation of any EphA2 variant is found to occur even without ephrin stimulation when the EphA2 content in cells is sufficiently high. Ephrin-A3 binding is not affected in mutant variants. Mutations in the TMD have a significant effect on EphA2 activity. Both ligand-dependent and ligand-independent activities are enhanced for the HR variant and reduced for the GZ variant compared with the WT. These findings allow us to suggest TMD dimerization switching between the heptad repeat and glycine zipper motifs, corresponding to inactive and active receptor states, respectively, as a mechanism underlying EphA2 signal transduction.

    ID:1139
  10. Petushkov V.N., Dubinnyi M.A., Tsarkova A.S., Rodionova N.S., Baranov M.S., Kublitski V.S., Shimomura O., Yampolsky I.V. (2014). A Novel Type of Luciferin from the Siberian Luminous Earthworm Fridericia heliota: Structure Elucidation by Spectral Studies and Total Synthesis. Angew. Chem. Int. Ed. Engl. 53 (22), 5566–5568 [+]

    Press-release on this article: "Novel luciferin from Siberian bioluminescent worm".

    ID:1016
  11. Petushkov V.N., Dubinnyi M.A., Rodionova N.S., Nadezhdin K.D., Marques S.M., EstevesdaSilva J.C.G., Shimomura O., Yampolsky I.V. (2014). AsLn2, a luciferin-related modified tripeptide from the bioluminescent earthworm Fridericia heliota. Tetrahedron Lett. 55 (2), 463–465 ID:1039
  12. Petushkov V.N., Tsarkova A.S., Dubinnyi M.A., Rodionova N.S., Marques S.M., EstevesdaSilva J.C.G., Shimomura O., Yampolsky I.V. (2014). CompX, a luciferin-related tyrosine derivative from the bioluminescent earthworm Fridericia heliota. Tetrahedron Lett. 55 (2), 460–462 ID:1040
  13. Mineev K.S., Lesovoy D.M., Usmanova D.R., Goncharuk S.A., Shulepko M.A., Lyukmanova E.N., Kirpichnikov M.P., Bocharov E.V., Arseniev A.S. (2013). NMR-based approach to measure the free energy of transmembrane helix-helix interactions. Biochim. Biophys. Acta 1838 (1PB), 164–172 [+]

    Knowledge of the energetic parameters of transmembrane helix-helix interactions is necessary for the establishment of a structure-energy relationship for α-helical membrane domains. A number of techniques have been developed to measure the free energies of dimerization and oligomerization of transmembrane α-helices, and all of these have their advantages and drawbacks. In this study we propose a methodology to determine the magnitudes of the free energy of interactions between transmembrane helices in detergent micelles. The suggested approach employs solution nuclear magnetic resonance (NMR) spectroscopy to determine the population of the oligomeric states of the transmembrane domains and introduces a new formalism to describe the oligomerization equilibrium, which is based on the assumption that both the dimerization of the transmembrane domains and the dissociation of the dimer can occur only upon the collision of detergent micelles. The technique has three major advantages compared with other existing approaches: it may be used to analyze both weak and relatively strong dimerization/oligomerization processes, it works well for the analysis of complex equilibria, e.g. when monomer, dimer and high-order oligomer populations are simultaneously present in the solution, and it can simultaneously yield both structural and energetic characteristics of the helix-helix interaction under study. The proposed methodology was applied to investigate the oligomerization process of transmembrane domains of fibroblast growth factor receptor 3 (FGFR3) and vascular endothelium growth factor receptor 2 (VEGFR2), and allowed the measurement of the free energy of dimerization of both of these objects. In addition the proposed method was able to describe the multi-state oligomerization process of the VEGFR2 transmembrane domain.

    ID:967
  14. Gushchin I., Chervakov P., Kuzmichev P., Popov A.N., Round E., Borshchevskiy V., Ishchenko A., Petrovskaya L., Chupin V., Dolgikh D.A., Arseniev A.S., Kirpichnikov M., Gordeliy V. (2013). Structural insights into the proton pumping by unusual proteorhodopsin from nonmarine bacteria. Proc. Natl. Acad. Sci. U.S.A. 110 (31), 12631–6 [+]

    Light-driven proton pumps are present in many organisms. Here, we present a high-resolution structure of a proteorhodopsin from a permafrost bacterium, Exiguobacterium sibiricum rhodopsin (ESR). Contrary to the proton pumps of known structure, ESR possesses three unique features. First, ESR's proton donor is a lysine side chain that is situated very close to the bulk solvent. Second, the α-helical structure in the middle of the helix F is replaced by 3(10)- and π-helix-like elements that are stabilized by the Trp-154 and Asn-224 side chains. This feature is characteristic for the proteorhodopsin family of proteins. Third, the proton release region is connected to the bulk solvent by a chain of water molecules already in the ground state. Despite these peculiarities, the positions of water molecule and amino acid side chains in the immediate Schiff base vicinity are very well conserved. These features make ESR a very unusual proton pump. The presented structure sheds light on the large family of proteorhodopsins, for which structural information was not available previously.

    ID:1260
  15. Volynsky P.E., Polyansky A.A., Fakhrutdinova G.N., Bocharov E.V., Efremov R.G. (2013). Role of Dimerization Efficiency of Transmembrane Domains in Activation of Fibroblast Growth Factor Receptor 3. J. Am. Chem. Soc. , [+]

    Mutations in transmembrane (TM) domains of receptor tyrosine kinases are shown to cause a number of inherited diseases and cancer development. Here, we use a combined molecular modeling approach to understand molecular mechanism of effect of G380R and A391E mutations on dimerization of TM domains of human fibroblast growth factor receptor 3 (FGFR3). According to results of Monte Carlo conformational search in the implicit membrane and further molecular dynamics simulations, TM dimer of this receptor is able to form a number of various conformations, which differ significantly by the free energy of association in a full-atom model bilayer. The aforementioned mutations affect dimerization efficiency of TM segments and lead to repopulation of conformational ensemble for the dimer. Particularly, both mutations do not change the dimerization free energy of the predominant (putative "non-active") symmetric conformation of TM dimer, while affect dimerization efficiency of its asymmetric ("intermediate") and alternative symmetric (putative "active") models. Results of our simulations provide novel atomistic prospective of the role of G380 and A391E mutations in dimerization of TM domains of FGFR3 and their consecutive contributions to the activation pathway of the receptor.

    ID:972
  16. Shenkarev Z.O., Paramonov A.S., Lyukmanova E.N., Gizatullina A.K., Zhuravleva A.V., Tagaev A.A., Yakimenko Z.A., Telezhinskaya I.N., Kirpichnikov M.P., Ovchinnikova T.V., Arseniev A.S. (2013). Peptaibol antiamoebin I: spatial structure, backbone dynamics, interaction with bicelles and lipid-protein nanodiscs, and pore formation in context of barrel-stave model. Chem. Biodivers. 10 (5), 838–63 [+]

    Antiamoebin I (Aam-I) is a membrane-active peptaibol antibiotic isolated from fungal species belonging to the genera Cephalosporium, Emericellopsis, Gliocladium, and Stilbella. In comparison with other 16-amino acid-residue peptaibols, e.g., zervamicin IIB (Zrv-IIB), Aam-I possesses relatively weak biological and channel-forming activities. In MeOH solution, Aam-I demonstrates fast cooperative transitions between right-handed and left-handed helical conformation of the N-terminal (1-8) region. We studied Aam-I spatial structure and backbone dynamics in the membrane-mimicking environment (DMPC/DHPC bicelles)(1) ) by heteronuclear (1) H,(13) C,(15) N-NMR spectroscopy. Interaction with the bicelles stabilizes the Aam-I right-handed helical conformation retaining significant intramolecular mobility on the ms-μs time scale. Extensive ms-μs dynamics were also detected in the DPC and DHPC micelles and DOPG nanodiscs. In contrast, Zrv-IIB in the DPC micelles demonstrates appreciably lesser mobility on the μs-ms time scale. Titration with Mn(2+) and 16-doxylstearate paramagnetic probes revealed Aam-I binding to the bicelle surface with the N-terminus slightly immersed into hydrocarbon region. Fluctuations of the Aam-I helix between surface-bound and transmembrane (TM) state were observed in the nanodisc membranes formed from the short-chain (diC12 : 0) DLPC/DLPG lipids. All the obtained experimental data are in agreement with the barrel-stave model of TM pore formation, similarly to the mechanism proposed for Zrv-IIB and other peptaibols. The observed extensive intramolecular dynamics explains the relatively low activity of Aam-I.

    ID:978
  17. Shenkarev Z.O., Panteleev P.V., Balandin S.V., Gizatullina A.K., Altukhov D.A., Finkina E.I., Kokryakov V.N., Arseniev A.S., Ovchinnikova T.V. (2012). Recombinant expression and solution structure of antimicrobial peptide aurelin from jellyfish Aurelia aurita. Biochem. Biophys. Res. Commun. 429 (1-2), 63–9 [+]

    Aurelin is a 40-residue cationic antimicrobial peptide isolated from the mezoglea of a scyphoid jellyfish Aurelia aurita. Aurelin and its (15)N-labeled analogue were overexpressed in Escherichia coli and purified. Antimicrobial activity of the recombinant peptide was examined, and its spatial structure was studied by NMR spectroscopy. Aurelin represents a compact globule, enclosing one 3(10)-helix and two α-helical regions cross-linked by three disulfide bonds. The peptide binds to anionic lipid (POPC/DOPG, 3:1) vesicles even at physiological salt concentration, it does not interact with zwitterionic (POPC) vesicles and interacts with the DPC micelle surface with moderate affinity via two α-helical regions. Although aurelin shows structural homology to the BgK and ShK toxins of sea anemones, its surface does not possess the "functional dyad" required for the high-affinity interaction with the K(+)-channels. The obtained data permit to correlate the modest antibacterial properties and membrane activity of aurelin.

    ID:977
  18. Konshina A.G., Dubovskii P.V., Efremov R.G. (2012). Structure and dynamics of cardiotoxins. Curr. Protein Pept. Sci. 13 (6), 570–84 [+]

    Cytotoxins (or cardiotoxins; CTs) are toxins from cobra venom characterized by the three-finger (TF) fold. CTs are on average 60-residue-long peptides, possessing as many as 4 disulfide bonds. The elements of antiparallel β-structure take origin from the hydrophobic core formed by the disulfides. The β-strands adopt the shape of the three loops, giving the name of the fold. While neurotoxins (NTs) - also TF proteins from snake venom - exert their effect through specific interactions with protein receptors, no specific protein target has been found for CTs. Unlike NTs, CTs are amphiphilic and cytotoxic against a variety of cells, including cancer ones. Thus, the hypothesis that the activity of CTs is caused by their interactions with lipid membranes is currently central. To understand molecular basis behind variations in toxicities of CTs highly homologous in their sequences, detailed knowledge of their structure and dynamics is required. The present review summarizes experimental and computational data on the spatial organization of CTs and their dynamics in various environments (aqueous solution, membranous milieus).

    ID:772
  19. Semenova A.A., Chugunov A.O., Dubovskii P.V., Chupin V.V., Volynsky P.E., Boldyrev I.A. (2011). The role of chain rigidity in lipid self-association: Comparative study of dihexanoyl- and disorbyl-phosphatidylcholines. Chem. Phys. Lipids 165, 382–386 [+]

    In the course of structure-function investigations of lipids a phosphatidylcholine molecule with short and rigid tails, di-2,4-hexadienoylphosphatidylcholine (DiSorbPC), was synthesized and studied in comparison with its saturated analog, dihexanoylphosphatidylcholine (DHPC). Conjugated double bonds in the acyl chains in DiSorbPC reduce considerably the number of possible conformers of the lipid within an aggregate. This leads to impaired packing of unsaturated acyl chains and thus, to a surprisingly high (115Å(2)) area per molecule for DiSorbPC at the air-water interface and failure to form micelles of regular size and shape. Details on DiSorbPC aggregation and packing provided by a set of experimental techniques combined with molecular dynamics simulations are presented.

    ID:669
  20. Shenkarev Z.O., Balandin S.V., Trunov K.I., Paramonov A.S., Sukhanov S.V., Barsukov L.I., Arseniev A.S., Ovchinnikova T.V. (2011). Molecular mechanism of action of β-hairpin antimicrobial peptide arenicin: oligomeric structure in dodecylphosphocholine micelles and pore formation in planar lipid bilayers. Biochemistry 50 (28), 6255–65 [+]

    The membrane-active, cationic, β-hairpin peptide, arenicin, isolated from marine polychaeta Arenicola marina exhibits a broad spectrum of antimicrobial activity. The peptide in aqueous solution adopts the significantly twisted β-hairpin conformation without pronounced amphipathicity. To assess the mechanism of arenicin action, the spatial structure and backbone dynamics of the peptide in membrane-mimicking media and its pore-forming activity in planar lipid bilayers were studied. The spatial structure of the asymmetric arenicin dimer stabilized by parallel association of N-terminal strands of two β-hairpins was determined using triple-resonance nuclear magnetic resonance (NMR) spectroscopy in dodecylphosphocholine (DPC) micelles. Interaction of arenicin with micelles and its oligomerization significantly decreased the right-handed twist of the β-hairpin, increased its amphipathicity, and led to stabilization of the peptide backbone on a picosecond to nanosecond time scale. Relaxation enhancement induced by water-soluble (Mn(2+)) and lipid-soluble (16-doxylstearate) paramagnetic probes pointed to the dimer transmembrane arrangement. Qualitative NMR and circular dichroism study of arenicin-2 in mixed DPC/1,2-dioleoyl-sn-glycero-3-phosphoglycerol bicelles, sodium dodecyl sulfate micelles, and lipid vesicles confirmed that a similar dimeric assembly of the peptide was retained in membrane-mimicking systems containing negatively charged lipids and detergents. Arenicin-induced conductance was dependent on the lipid composition of the membrane. Arenicin low-conductivity pores were detected in the phosphatidylethanolamine-containing lipid mixture, whereas the high-conductivity pores were observed in an exclusively anionic lipid system. The measured conductivity levels agreed with the model in which arenicin antimicrobial activity was mediated by the formation of toroidal pores assembled of two, three, or four β-structural peptide dimers and lipid molecules. The structural transitions involved in arenicin membrane-disruptive action are discussed.

    ID:535
  21. Shenkarev Z.O., Finkina E.I., Nurmukhamedova E.K., Balandin S.V., Mineev K.S., Nadezhdin K.D., Yakimenko Z.A., Tagaev A.A., Temirov Y.V., Arseniev A.S., Ovchinnikova T.V. (2010). Isolation, structure elucidation, and synergistic antibacterial activity of a novel two-component lantibiotic lichenicidin from Bacillus licheniformis VK21. Biochemistry 49 (30), 6462–72 [+]

    A novel synergetic lantibiotic pair, Lchalpha(3249.51 Da) and Lchbeta(3019.36 Da), termed lichenicidin VK21, was isolated from the producer strain Bacillus licheniformis VK21. Chemical and spatial structures of Lchalphaand Lchbeta were determined. Each peptide contains 31 amino acid residues linked by 4 intramolecular thioether bridges and the N-terminal 2-oxobutyryl group. Spatial structures of Lchalpha and Lchbetawere studied by NMR spectroscopy in methanol solution. Lchalpha peptide displays structural homology with mersacidin-like lantibiotics and involves relatively well-structured N- and C-terminal domains connected by a flexible loop stabilized by thioether bridge Ala11-S-Ala21. In contrast, the Lchbetapeptide represents prolonged hydrophobic alpha-helix flanked with more flexible N- and C-terminal domains. A lantibiotic cluster of the Bacillus licheniformis VK21 genome which comprises the structural genes, lchA1 and lchA2, encoding the lantibiotics precursors, as well as the gene of a modifying enzyme lchM1, was amplified and sequenced. The mature peptides, Lchalphaand Lchbetainteract synergistically to possess antibiotic activity against Gram-positive bacteria within a nanomolar concentration range, though the individual peptides were shown to be active at micromolar concentrations. Our results afford molecular insight into mechanism of lichenicidin VK21 action.

    ID:359
  22. Mineev K.S., Bocharov E.V., Pustovalova Y.E., Bocharova O.V., Chupin V.V., Arseniev A.S. (2010). Spatial Structure of the Transmembrane Domain Heterodimer of ErbB1 and ErbB2 Receptor Tyrosine Kinases. J. Mol. Biol. 400 (2), 231–243 [+]

    Growth factor receptor tyrosine kinases of the ErbB family play a significant role in vital cellular processes and various cancers. During signal transduction across plasma membrane, ErbB receptors are involved in lateral homodimerization and heterodimerization with proper assembly of their extracellular single-span transmembrane (TM) and cytoplasmic domains. The ErbB1/ErbB2 heterodimer appears to be the strongest and most potent inducer of cellular transformation and mitogenic signaling compared to other ErbB homodimers and heterodimers. Spatial structure of the heterodimeric complex formed by TM domains of ErbB1 and ErbB2 receptors embedded into lipid bicelles was obtained by solution NMR. The ErbB1 and ErbB2 TM domains associate in a right-handed alpha-helical bundle through their N-terminal double GG4-like motif T(648)G(649)X(2)G(652)A(653) and glycine zipper motif T(652)X(3)S(656)X(3)G(660), respectively. The described heterodimer conformation is believed to support the juxtamembrane and kinase domain configuration corresponding to the receptor active state. The capability for multiple polar interactions, along with hydrogen bonding between TM segments, correlates with the observed highest affinity of the ErbB1/ErbB2 heterodimer, implying an important contribution of the TM helix-helix interaction to signal transduction.

    ID:346
  23. Bocharov E.V., Mayzel M.L., Volynsky P.E., Mineev K.S., Tkach E.N., Ermolyuk Y.S., Schulga A.A., Efremov R.G., Arseniev A.S. (2010). Left-handed dimer of EphA2 transmembrane domain: Helix packing diversity among receptor tyrosine kinases. Biophys. J. 98 (5), 881–9 [+]

    The Eph receptor tyrosine kinases and their membrane-bound ephrin ligands control a diverse array of cell-cell interactions in the developing and adult organisms. During signal transduction across plasma membrane, Eph receptors, like other receptor tyrosine kinases, are involved in lateral dimerization and subsequent oligomerization presumably with proper assembly of their single-span transmembrane domains. Spatial structure of dimeric transmembrane domain of EphA2 receptor embedded into lipid bicelle was obtained by solution NMR, showing a left-handed parallel packing of the transmembrane helices (535-559)(2). The helices interact through the extended heptad repeat motif L(535)X(3)G(539)X(2)A(542)X(3)V(546)X(2)L(549) assisted by intermolecular stacking interactions of aromatic rings of (FF(557))(2), whereas the characteristic tandem GG4-like motif A(536)X(3)G(540)X(3)G(544) is not used, enabling another mode of helix-helix association. Importantly, a similar motif AX(3)GX(3)G as was found is responsible for right-handed dimerization of transmembrane domain of the EphA1 receptor. These findings serve as an instructive example of the diversity of transmembrane domain formation within the same family of protein kinases and seem to favor the assumption that the so-called rotation-coupled activation mechanism may take place during the Eph receptor signaling. A possible role of membrane lipid rafts in relation to Eph transmembrane domain oligomerization and Eph signal transduction was also discussed.

    ID:320
  24. Goncharuk S.A., Shulga A.A., Ermolyuk Y.S., Kuzmichev P.K., Sobol V.A., Bocharov E.V., Chupin V.V., Arseniev A.S., Kirpichnikov M.P. (2009). Bacterial synthesis, purification, and solubilization of membrane protein KCNE3, a regulator of voltage-gated potassium channels. Biochemistry Mosc. 74 (12), 1344–9 [+]

    An efficient method is described for production of membrane protein KCNE3 and its isotope labeled derivatives ((15)N-, (15)N-/13C-) in amounts sufficient for structural-functional investigations. The purified protein preparation within different detergent micelles was characterized using dynamic light scattering, CD spectroscopy, and NMR spectroscopy. It is shown that within DPC/LDAO micelles the protein is in monomeric form and acquires mainly alpha-helical conformation. The existence of cross-peaks for all glycines of the (15)N-HSQC NMR spectra as well as relatively small line widths (~20 Hz) confirm the high quality of the preparation and the possibility of obtaining structural-dynamic information on KCNE3 by high resolution heteronuclear NMR spectroscopy.

    ID:273
  25. Shenkarev Z.O., Lyukmanova E.N., Solozhenkin O.I., Gagnidze I.E., Nekrasova O.V., Chupin V.V., Tagaev A.A., Yakimenko Z.A., Ovchinnikova T.V., Kirpichnikov M.P., Arseniev A.S. (2009). Lipid-protein nanodiscs: possible application in high-resolution NMR investigations of membrane proteins and membrane-active peptides. Biochemistry Mosc. 74 (7), 756–65 [+]

    High-resolution NMR is shown to be applicable for investigation of membrane proteins and membrane-active peptides embedded into lipid-protein nanodiscs (LPNs). (15)N-Labeled K+-channel from Streptomyces lividans (KcsA) and the antibiotic antiamoebin I from Emericellopsis minima (Aam-I) were embedded in LPNs of different lipid composition. Formation of stable complexes undergoing isotropic motion in solution was confirmed by size-exclusion chromatography and (31)P-NMR spectroscopy. The 2D 1H-(15)N-correlation spectra were recorded for KcsA in the complex with LPN containing DMPC and for Aam-I in LPNs based on DOPG, DLPC, DMPC, and POPC. The spectra recorded were compared with those in detergent-containing micelles and small bicelles commonly used in high-resolution NMR spectroscopy of membrane proteins. The spectra recorded in LPN environments demonstrated similar signal dispersion but significantly increased (1)H(N) line width. The spectra of Aam-I embedded in LPNs containing phosphatidylcholine showed significant selective line broadening, thus suggesting exchange process(es) between several membrane-bound states of the peptide. (15)N relaxation rates were measured to obtain the effective rotational correlation time of the Aam-I molecule. The obtained value (approximately 40 nsec at 45 degrees C) is indicative of additional peptide motions within the Aam-I/LPN complex.

    ID:353
  26. Stavrakoudis A., Tsoulos I.G., Shenkarev Z.O., Ovchinnikova T.V. (2009). Molecular dynamics simulation of antimicrobial peptide arenicin-2: beta-hairpin stabilization by noncovalent interactions. Biopolymers 92 (3), 143–55 [+]

    Arenicin-2 is a 21 residue antimicrobial cyclic peptide, possessing one disulphide bond between residues Cys(3) and Cys(20). NMR and CD studies suggested that the structure of arenicin-2 in water represented a well formed, but highly twisted beta-hairpin. To investigate the spatial arrangement of the peptide side chains and to get a clear view of its possible amphipathic properties we performed molecular dynamics in explicit water. Four independent trajectories, 50 ns in length, were produced, starting from various initial conformations or by applying different simulation conditions. Arenicin-2 retained its beta-hairpin structure during simulations, although the residues close to strand ends were found to escape from the ideal hairpin conformation. The type I' beta-turn connecting the two strands fluctuated between type IV and II' beta-turn. Conversely, the right-handed twist of the beta-hairpin was well conserved with average twist value 203 degrees +/- 19 degrees per eight residues. Several nonbonded interactions, like hydrophobic interactions between aliphatic side chains, cation/pi-aromatic interactions, CH...pi aromatic bond and water bridges, contributed to the hairpin stabilization.

    ID:410
  27. Ovchinnikova T.V., Shenkarev Z.O., Balandin S.V., Nadezhdin K.D., Paramonov A.S., Kokryakov V.N., Arseniev A.S. (2008). Molecular insight into mechanism of antimicrobial action of the beta-hairpin peptide arenicin: specific oligomerization in detergent micelles. Biopolymers 89 (5), 455–64 [+]

    Arenicins are 21-residue cationic antimicrobial peptides isolated from marine polychaeta Arenicola marina. The peptides exhibit potent broad-spectrum antimicrobial activity. In water solution arenicin-2 adopts a beta-hairpin conformation, stabilized by one disulfide and nine hydrogen bonds. To determine the propensity for the peptide oligomerization in membrane mimetic systems, the recombinant arenicin-2 was overexpressed as a fused form in Escherichia coli. The arenicin-2 oligomerization and intermolecular packing in membrane mimicking environment were investigated using high-resolution NMR spectroscopy. The present studies show that arenicin-2 preserves a beta-hairpin structure and forms asymmetric dimers upon incorporation into the dodecylphosphocholine micelle. Two monomers of arenicin-2 are aligned parallel to each other by the N-terminal strands of the beta-hairpin (CN upward arrow upward arrowNC type of association). Polyacrylamide gel electrophoresis analysis indicated that in environment of anionic SDS micelles the arenicin-2 might undergo further oligomerization and form tetramers. Our results afford further molecular insight into possible mechanism of antimicrobial action of arenicins.

    ID:414
  28. Dubovskii P.V., Volynsky P.E., Polyansky A.A., Karpunin D.V., Chupin V.V., Efremov R.G., Arseniev A.S. (2008). Three-dimensional structure/hydrophobicity of latarcins specifies their mode of membrane activity. Biochemistry 47 (11), 3525–33 [+]

    Latarcins, linear peptides from the Lachesana tarabaevi spider venom, exhibit a broad-spectrum antimicrobial activity, likely acting on the bacterial cytoplasmic membrane. We study their spatial structures and interaction with model membranes by a combination of experimental and theoretical methods to reveal the structure-activity relationship. In this work, a 26 amino acid peptide, Ltc1, was investigated. Its spatial structure in detergent micelles was determined by (1)H nuclear magnetic resonance (NMR) and refined by Monte Carlo simulations in an implicit water-octanol slab. The Ltc1 molecule was found to form a straight uninterrupted amphiphilic helix comprising 8-23 residues. A dye-leakage fluorescent assay and (31)P NMR spectroscopy established that the peptide does not induce the release of fluorescent marker nor deteriorate the bilayer structure of the membranes. The voltage-clamp technique showed that Ltc1 induces the current fluctuations through planar membranes when the sign of the applied potential coincides with the one across the bacterial inner membrane. This implies that Ltc1 acts on the membranes via a specific mechanism, which is different from the carpet mode demonstrated by another latarcin, Ltc2a, featuring a helix-hinge-helix structure with a hydrophobicity gradient along the peptide chain. In contrast, the hydrophobic surface of the Ltc1 helix is narrow-shaped and extends with no gradient along the axis. We have also disclosed a number of peptides, structurally homologous to Ltc1 and exhibiting similar membrane activity. This indicates that the hydrophobic pattern of the Ltc1 helix and related antimicrobial peptides specifies their activity mechanism. The latter assumes the formation of variable-sized lesions, which depend upon the potential across the membrane.

    ID:315
  29. Bocharov E.V., Mineev K.S., Volynsky P.E., Ermolyuk Y.S., Tkach E.N., Sobol A.G., Chupin V.V., Kirpichnikov M.P., Efremov R.G., Arseniev A.S. (2008). Spatial structure of the dimeric transmembrane domain of the growth factor receptor ErbB2 presumably corresponding to the receptor active state. J. Biol. Chem. 283 (11), 6950–6 [+]

    Proper lateral dimerization of the transmembrane domains of receptor tyrosine kinases is required for biochemical signal transduction across the plasma membrane. The spatial structure of the dimeric transmembrane domain of the growth factor receptor ErbB2 embedded into lipid bicelles was obtained by solution NMR, followed by molecular dynamics relaxation in an explicit lipid bilayer. ErbB2 transmembrane segments associate in a right-handed alpha-helical bundle through the N-terminal tandem GG4-like motif Thr652-X3-Ser656-X3-Gly660, providing an explanation for the pathogenic power of some oncogenic mutations.

    ID:314
  30. Lyukmanova E.N., Shenkarev Z.O., Paramonov A.S., Sobol A.G., Ovchinnikova T.V., Chupin V.V., Kirpichnikov M.P., Blommers M.J., Arseniev A.S. (2008). Lipid-protein nanoscale bilayers: a versatile medium for NMR investigations of membrane proteins and membrane-active peptides. J. Am. Chem. Soc. 130 (7), 2140–1 ID:356
  31. Ovchinnikova T.V., Shenkarev Z.O., Nadezhdin K.D., Balandin S.V., Zhmak M.N., Kudelina I.A., Finkina E.I., Kokryakov V.N., Arseniev A.S. (2007). Recombinant expression, synthesis, purification, and solution structure of arenicin. Biochem. Biophys. Res. Commun. 360 (1), 156–62 [+]

    Arenicins are 21-residue cationic antimicrobial peptides, isolated from marine polychaeta Arenicola marina. In order to determine a high-resolution three-dimensional structure of arenicin-2, the recombinant peptide was overexpressed as a fused form in Escherichia coli. Both arenicin isoforms were synthesized using the Fmoc-based solid-phase strategy. Recombinant and synthetic arenicins were purified, and their antimicrobial and spectroscopic properties were analyzed. NMR investigation shows that in water solution arenicin-2 displays a prolonged beta-hairpin, formed by two antiparallel beta-strands and stabilized by one disulfide and nine hydrogen bonds. A significant right-handed twist in the beta-sheet is deprived the peptide surface of amphipathicity. CD spectroscopic analysis indicates that arenicin-2 binds to the SDS and DPC micelles, and conformation of the peptide is significantly changed upon binding. Arenicin strongly binds to anionic lipid (POPE/POPG) vesicles in contrast with zwitterionic (POPC) ones. These results suggest that arenicins are membrane active peptides and point to possible mechanism of their selectivity toward bacterial cells.

    ID:419
  32. Shenkarev Z.O., Paramonov A.S., Nadezhdin K.D., Bocharov E.V., Kudelina I.A., Skladnev D.A., Tagaev A.A., Yakimenko Z.A., Ovchinnikova T.V., Arseniev A.S. (2007). Antiamoebin I in methanol solution: rapid exchange between right-handed and left-handed 3(10)-helical conformations. Chem. Biodivers. 4 (6), 1219–42 [+]

    Antiamoebin I (Aam-I) is a membrane-active peptaibol antibiotic isolated from fungal species belonging to the genera Cephalosporium, Emericellopsis, Gliocladium, and Stilbella. Antiamoebin I has the amino acid sequence: Ac-Phe(1)-Aib-Aib-Aib-Iva-Gly-Leu-Aib(8)-Aib-Hyp-Gln-Iva-Hyp-Aib-Pro-Phl(16). By using the uniformly (13)C,(15)N-labeled sample of Aam-I, the set of conformationally dependent J couplings and (3h)J(NC) couplings through H-bonds were measured. Analysis of these data along with the data on magnetic nonequivalence of the (13)C(beta) nuclei (Deltadelta((13)C(beta))) in Aib and Iva residues allowed us to draw the univocal conclusion that the N-terminal part (Phe(1)-Gly(6)) of Aam-I in MeOH solution is in fast exchange between the right-handed and left-handed 3(10)-helical conformations, with an approximately equal population of both states. An additional conformational exchange process was found at the Aib(8) residue. The (15)N-NMR-relaxation and CD-spectroscopy measurements confirmed these findings. Molecular modeling and Monte Carlo simulations revealed that both exchange processes are correlated and coupled with significant hinge-bending motions around the Aib(8) residue. Our results explain relatively low activity of Aam-I with respect to other 15-amino acid residue peptaibols (for example, zervamicin) in functional and biological tests. The high dynamic 'propensity' possibly prevents both initial binding of the antiamoebin to the membrane and subsequent formation of stable ionic channels according to the barrel-stave mechanism.

    ID:418
  33. Volynsky P.E., Bocharov E.V., Nolde D.E., Vereshaga Y.A., Mayzel M.L., Mineev K.S., Mineeva E.V., Pustovalova Yu.E., Gagnidze I.A., Efremov R.G., Arseniev A.S. (2006). Solution of the Spatial Structure of Dimeric Transmembrane Domains of Proteins by Heteronuclear NMR Spectroscopy and Molecular Modeling. Biophysics 51 (S1), S23–S27 [+]

    Membrane proteins play an important role in various biological processes. An approach combining
    NMR spectroscopy with molecular modeling was used to study the spatial structure and intramolecular dynamics of protein transmembrane domains consisting of two interacting α-helices. The approach was tested with model transmembrane domains and yielded detailed atomic-level data on the protein–protein and protein–lipid interactions.

    ID:347
  34. Orekhov V.Y., Nolde D.E., Golovanov A.P., Korzhnev D.M., Arseniev A.S. (1995). Processing of heteronuclear NMR relaxation data with the new software DASHA. Appl. Mag. Reson. 9 (4), 581–588 [+]

    The new program DASHA is an efficient implementation of common data processing steps for the protein internal dynamic analysis. The “model-free” parameters and their uncertainties (Lipari G., Szabo A.: J. Am. Chem. Soc.104, 4546–4559 (1982) can be calculated from an arbitrary combination of experimental data sets (i.e. heteronuclear1H−15N or1H−13C relaxation times and NOE values at different spectrometer frequencies). Anisotropy of the molecular rotational diffusion could be also taken into account without introduction of the new adjustable parameters into the spectral density functionJ(ω), provided the structure of the molecule is known. Parameters of chemical (conformational) exchange can be estimated from the CPMG spin-lock frequency dependences (Bloomet al.: J. Chem. Phys.42, 1615–1624 (1965); Orekhovet al.: Eur. J. Biochem.219, 887–896 (1994). The program can be used both in the interactive and batch modes. It has sophisticated PostScript plotting facilities.

    ID:1046
  35. Arseniev A.S., Bystrov V.F., Lomize A.L., Ovchinnikov Yu.A. (1985). 1H-NMR study of gramicidin A transmembrane ion channel. Head-to-head right-handed, single-stranded helices. FEBS Lett. 186 (2), 168–174 [+]

    The structure of [Val1] gramicidin A incorporated into sodium dodecyl-d25 sulphate micelles has been studied by two-dimensional proton NMR spectroscopy. Analysis of nuclear Overhauser effects, spin-spin couplings and solvent accessibility of NH groups show that the conformation of the Na+ complex of gramicidin A in detergent micelles, which in many ways mimic the phospholipid bilayer of biomembranes, is an N-terminal to N-terminal (head-to-head) dimer Image formed by two right-handed, single-stranded β6.3 helices with 6.3 residues per turn, differing from Urry's structure by handedness of the helices.

    ID:144
  36. Bystrov V.F., Ivanov V.T., Portnova S.L., Balashova T.A., Ovchinnikov Yu.A. (1973). Refinement of the angular dependence of the peptide vicinal NH-CaH coupling constant. Tetrahedron 29 (6), 873–877 [+]

    The refined dependence of the peptide NHCαH vicinal coupling constant on the dihedral angle θ have been derived on the basis of the accumulated experimental data. The mean permissible values (in Hz) are approximated by 3JNHCH = 9·4 cos2 θ - 1·1 cos θ + 0·4 An analogous relationship for the sum of two vicinal NH-CαH2 coupling constants in the glycyl residue have been calculated from the above dependence. Measurements on N-methylacetamide in various solvents and in the presence of an alkali salt showed the vicinal constant NH-CH to vary by not more than ± 3%. Some of the other proposed 3JNHCH(θ) dependencies give too low values for the cis-oriented NH and CαH bonds. This may be due to the fact that in these correlations the data for compounds with cis-amide bonds have been used for 0° - θ - 90° region of the dependence.

    ID:1044
  37. Bystrov V.F., Dubrovina N.I., Barsukov L.I., Bergelson L.D. (1971). NMR differentiation of the internal and external phospholipid membrane surfaces using paramagnetic Mn2+ and Eu3+ ions. Chem. Phys. Lipids 6 (4), 343–350 [+]

    The effect of paramagnetic Mn2+ and Eu3+ ions on the NMR spectra of sonicated lecithin dispersions in water and benzene has been investigated. In aqueous dispersions containing paramagnetic ions the N+(CH3)3 signal of the lecithin molecules in the lipid bilayer consists of two components, one broadened by Mn2+ and shifted to high field by Eu3+ must correspond to molecules in the external surface in contact with the bulk salt solution, and the other corresponding to internal lecithin molecules in contact with the ion free internal aqueous phase. Thus the external and internal surfaces of a lecithin containing membrane can be discriminated. The rates of exchange of the paramagnetic ions, of the lecithin and the water molecules between micelles and/or between micelles and external medium have been evaluated.

    ID:1045

Head of the laboratory

Alexander Arseniev

  • Russia, Moscow, Ul. Miklukho-Maklaya 16/10 — On the map
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  • E-mail: aars@nmr.ru
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