Relaxation times librational state

The hydration dependence studies of the internal protein dynamics of hen egg white lysozyme by and H NMR relaxation have been presented. The relaxation times were quantitatively analysed by the well-established correlation function formalism and model-free approach. The obtained data was described by a model based on three types of motion having correlation times around 10 , 10 and 10 s. The slowest process was shown to originate from correlated conformational transitions between different energy minima. The intermediate process was attributed to librations within one energy minimum, and the fastest one was identified as a fast rotation of methyl protons around the symmetry axis of methyl groups. A comparison of the dynamic behaviour of lysozyme and polylysine obtained from a previous study revealed that in the dry state both biopolymers are rigid on both fast and slow time scales. Upon hydration, lysozyme and polylysine showed a considerable enhancement of the internal mobility. The side chain fragments of polylysine were more mobile than those of lysozyme, whereas the backbone of lysozyme was found to be more mobile than that of polylysine. 

The time evolutions of the ground state hole widths in acetonitrile (1) and methanol (2) solutions are plotted in Fig. 6. The hole widths broadened up to 200-300cm in the instmmental response time of the system in the all solvents used here. The band width of the fluorescence spectrum of aesyl violet in methanol/ethanol mixed glass solvent at 77K was also observed as about 300cm hwhm. The rapid relaxation within the response time observed in the hole spectrum as well as the relaxation m 77K glass may correspond to the relaxation due to the librational or inertial component of the solvent which was reported in the studies of dynamic Stokes shift in femtosecond region . ... 

Solution and solid state studies of non-classical transition metal hydride systems have revealed fast intramolecular motions of the dihydrogen ligands [7, 8]. These motions represent a rotational diffusion around the axis perpendicular to the H-H (or D-D) vector (Scheme 1), a libration (Scheme 2) or 180° - jumps (Scheme 3) around the same axis [43]. It has been shown that the type of motion, its frequency and the orientation of eq z (angle a in Scheme I) affect strongly on the 2H NMR parameters, causing an elongation of the H T, time in solution [25] or a decrease of the quadrupole splitting in the solid -state H NMR spectra [22]. This influence creates additional problems for DQCC determinations from experimental relaxation measurements or solid state NMR data, particularly when the orientation of the eqzz vector is unknown. 

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