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Quasielastic neutron scattering spectra were measured for pure acetonitrile at 25 °C. In the framework of a simple model of translation and rotation, it was found that the short-time self-diffusion coefficient of liquid acetonitrile is similar to the long-time one measured by NMR. As far as the rotational motion is concerned, the characteristic time was found to be close to the typical value of the molecule spinning motion. The complete inelastic and quasielastic spectra may be further used to check the results of molecular dynamics simulations of acetonitrile. [ABSTRACT FROM AUTHOR]

The structure around lithium counterions in polyacrylate solutions has been investigated by neutron diffraction, and it is concluded that small cations remain hydrated when they accumulate around a highly charged polymer. Interactions between the polyion and the counterions over a range outside the hydration shell are also observed. The relaxation rate of 7Li due to dipolar coupling to 17O was obtained by nuclear magnetic resonance. The results indicate that the polyion exerts a moderate influence on the reorientational dynamics of the lithium aqua-ion. [ABSTRACT FROM AUTHOR]

Abstract: It is well known that water plays a major role in the stability and catalytic function of proteins. Both the effect of hydration water on the dynamics of proteins and the effect of proteins on the dynamics of water have been studied using inelastic neutron scattering. Dynamic neutron scattering is the most direct probe of diffusive and collective protein dynamics on the picosecond–nanosecond timescale. We present here results for C-phycocyanin, which is a globular protein important for photosynthesis. It can be obtained in protonated and deuterated forms. Diffusive motions have been studied using the protonated C-phycocyanin protein. The collective dynamics has been investigated using the fully deuterated C-phycocyanin protein. Comparison is made with results of molecular dynamics simulation. [Copyright &y& Elsevier]

Abstract: We have studied the influence of temperature on the structure of BPTI in solution by small angle neutron scattering. We have investigated the variation of the radius of gyration and the modification of the shape of BPTI between ambient temperature and 368 K. Results have shown an increase of the radius of gyration from 10.9 Å at ambient temperature up to 13.3 Å at 368 K. Global and internal dynamics of BPTI in solution were studied by quasielastic neutron scattering. The analysis of neutron data in terms of intermediate scattering function reveals two relaxation times τ 1 and τ 2 related respectively to global translational diffusive motions and to internal motions of protein. Motions of protons belonging to lateral chains of residues located at the surface of the protein have been detected. The results are compared to the recently published results concerning the influence of pressure on structure and dynamics of BPTI in solution [Appavou MS et al. Biochimica et Biophysica Acta, 1764, 2006, pp 414–423]. [Copyright &y& Elsevier]

Abstract: This paper presents a study of the influence of non-denaturing hydrostatic pressure on the relaxation dynamics of lysozyme in solution, which combines molecular dynamics simulations and quasielastic neutron scattering experiments. We compare results obtained at ambient pressure and at 3kbar. Experiments have been performed at pD 4.6 and at a protein concentration of 60mg/ml. For both pressures we checked the monodispersity of the protein solution by small angle neutron scattering. To interpret the simulation results and the experimental data, we adopt the fractional Ornstein–Uhlenbeck process as a model for the internal relaxation dynamics of the protein. On the experimental side, global protein motions are accounted for by the model of free translational diffusion, neglecting the much slower rotational diffusion. We find that the protein dynamics in the observed time window from about 1 to 100ps is slowed down under pressure, while its fractal characteristics is preserved, and that the amplitudes of the motions are reduced by about 20%. The slowing down of the relaxation is reduced with increasing q-values, where more localized motions are seen. [Copyright &y& Elsevier]