Molecular dynamics of membranes

The Use of 2H-NMR and 13C-NMR to Determine the Degree of Order and the Molecular Dynamics of Membranes... 

During 1994—2006, Vial was director of the Molecular Dynamics of Membrane Interactions laboratory, a joint laboratory between the French... 

Centre National de la Recherche Scientifique (CNRS, Paris, France) and the University of Montpellier II (Montpellier, France). Presently he is research director (DR1) at INSERM, director of CNRS University Montpellier 2 Laboratory (UMR 5539), Molecular Dynamics of Membrane Interactions, Health Department, biochemistry/pharmacology section. 

Biomembranes are complex structures composed of various lipids and proteins. Different membrane compositions affect viscoelastic and hydrodynamic properties of membranes, which are critical to their functions. Cholesterol-rich vesicles are similar to cell membranes in structure and component. Therefore, cholesterol-rich vesicles can represent a typical model for studying membrane dynamics and functions. Nuclear magnetic relaxation dispersion was used to investigate the detailed molecular dynamics of membrane differences between vesicles and cholesterol vesicles in the temperature range of 278-298 K. Vesicles of two different sizes were prepared. The effect of cholesterol mainly affected the order fluctuation of membranes and the diffusional motion of lipid molecules. ... 

IV. MOLECULAR DYNAMICS IN MEMBRANES A. Overview of Dynamic Processes in Membranes... 

B Roux, TB Woolf. Molecular dynamics of Pfl coat protein in a phospholipid bilayer. In KM Merz Ir, B Roux, eds. Biological Membranes A Molecular Perspective from Computation and Experiment. Boston Birkhauser, 1996, pp 555-587. 

The favourable properties which mark out vesicles as protocell models were confirmed by computer simulation (Pohorill and Wilson, 1995). These researchers studied the molecular dynamics of simple membrane/water boundary layers the bilayer surface fluctuated in time and space. The model membrane consisted of glycerine-1-monooleate defects were present which allowed ion transport to occur, whereby negative ions passed through the bilayer more easily than positive ions. The membrane-water boundary layer should be particularly suited to reactions which are accelerated by heterogeneous catalysis. Thus, the authors believe that these vesicles fulfil almost all the conditions required for the first protocells on earth ... 

Deuterium NMR (2H-NMR) is a powerful technique to obtain information on both the degree of order and the molecular dynamics of liquid crystalline media. It has extensively been used on model as well as natural membranes. Deuterium NMR has been used as a probe to investigate chain packing in lipid bilayers, and the effects of hydrocarbons and alcohols and their location in the membrane have been determined [123]. 

The first experimental evidences that electron transfer from QA to P+ and from QA to Qb in reaction centers are controlled by the protein conformational dynamics, was obtained in the late 1970 s (Berg 1978a,b Likhtenshtein et al., 1979 a, b) This conclusion was confirmed in subsequent experimental studies in which molecular dynamics of RC and the photsynthetic membrane were determined with a whole set of physical labels. (Kotelnikov et al., 1983, Kochetkov et al., 1984 Parak et al., 1983). It was shown that the electron transfer from reduced primary acceptor QA to secondary acceptor Qb takes place only under conditions in which the labels record the mobility of the protein moiety in the membrane with the correlation frequency u0 > 107 s-1 (Fig. 3.16). 

Lai, C. S., Joseph, J., and Shih, C. C. (1989), Molecular dynamics of antitumor ether-linked phospholipids in model membranes A spin-label study,Biochem. Biophys. Res. Commun., 160,1189-1195. 

Griac, P., and Henry, S.A., 1996, Phosphatidylcholine biosynthesis in Saccharomyces cerevisiae Effects on regulation of phospholipid synthesis and respiratory competence. In Op den Kamp, J.A.F. (ed.), NATO ASI Series Molecular Dynamics of Biological Membranes. Springer, Verlag, pp. 339-346. 

In one of our earlier applications, FCS diagnosed unanticipated micelle formation and led to the first development of confocal image microscopy for smaller focal volumes [3]. Recognizing the effective applications of fluorescent marker d mamics to understand cell membrane d mamics, we applied FCS to molecular diffusion on cell membranes, entering thereby into a long series of studies of the dynamics of membrane processes in life, which was at that time a quagmire of conflicting ideas [4]. Later, we also extended FCS theory to fluid flow analysis [9]. It has proven useful for a diversity of ultrafast chemical kinetics as well, c.f. [10-13]. 

Although biologic membranes serve as physical barriers, it is important to recognize that their molecular constituents are in a constant state of motional flux. Many different types of molecular motion are present in biological membranes including rotation, translation and libration, each of which contributes in important ways to the physical properties of cellular membranes. Since alterations in membrane physical properties have profound effects on the kinetics of many transmembrane enzymes and modulate the rates and types of interactions between proteins, it comes as no surprise that the molecular dynamics of a cell membrane is an important modulator of signal transduction (e.g., Lenaz, 1987). Thus, biological... 

At the present time, when the structure of the proton pumping protein and the membrane s surface can be gained at atomic resolution, when the dissociation of a proton can be recorded with sub-nanosecond resolution and molecular dynamics can be extended to tens of nanoseconds, it seems that a combination of these methods will be required to elucidate the mechanism of the reaction. Thus, combination of specific labeling of sites of interest by a photoacid or indicator, coupled with time-resolved measurements and molecular dynamics of the reaction, will be the next step in the research. Once these combined experiments are available, the generalization of the process, like the role of local electrostatic potential, orientation of water and the relative motion of side-chains, will be quantitated, with a subsequent improvement in the theoretical predicting power. 

Information on the effect of carotenoids on molecular dynamics of lipid membranes may be... 

In their discussion, Rahman and Stillinger anticipated further studies on molecular dynamics of water solutions under various conditions, including studies of the hydration of macromolecules and membranes. 

The result demonstrates the potential of PFG NMR to quantify molecular dynamics of the peptide binding to membranes. ... 

Membranes and model membranes exhibit liquid crystalline behavior and this has been exploited in a number of studies to obtain valuable information on the structure and dynamics of membrane associated peptides and proteins as well as on the interaction of the peptides with the membranes themselves. NMR spectroscopy of nuclei such as proton, carbon, deuterium, nitrogen and phosphorus has been utilized for such purposes. Structure elucidation of membrane-associated peptides and proteins in oriented bilayers by solid-state NMR spectroscopy has been reviewed. A survey on the use of static uniaxially oriented samples for structural and topological analysis of membrane-associated polypeptides is available. The theoretical background has been dealt with and a number of examples of applications provided. In addition, ongoing developments combining this method with information from solution NMR spectroscopy and molecular modelling as well as exploratory studies using dynamic nuclear polarization solid-state NMR have been presented. The use of N chemical shift anisotropy, dipolar interactions and the deuterium quadrupolar split-... 

C.F. Martins, L. Neves, I.M. Coelhoso, F. Vaca Chavez, J.G. Crespo, P.J. Sebastiao, Temperature effects on the molecular dynamics of modified NAFION membranes incorporating ionic liquids cations a NMRD study, Fuel Cells 13 (2013) 1166-1176. 

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