Polypeptides, local dynamics

Local Dynamics in Polypeptides Studied by Solid State 2H NMR Side Chain Dynamics of Poly(Y-benzyl L-glutamate) and Racemic Poly(Y-benzyl glutamate)... 

The first account is on Phase Incremented Pulses in NMR with Applications by S. Zhang, this is followed by Advances in NMR Studies of Liquid Crystals by R. Y. Dong, H. C. Bertram and H. J. Anderson report on Applications of NMR in Meat Science , NMR Characterization of Mechanical Waves is covered by G. Madelin, N. Baril, J. D. de Certaines, J.-M. Francone and E. Thiaudiere, the next account is on Aspects of Coherence Transfer in High Molecular Weight Proteins by P. Permi, the final chapter is on Local Dynamics in Polypeptides studied by Solid State 2H NMR by T. Hiraoki, S. Kitazawa and A. Tsutsumi. 

Relaxation-related work on proteins and polypeptides makes typically use of H, and NMR. A couple of papers have dealt with measurements on in fluorine-labelled aminoacids incorporated into peptide stuctures. Shi and co-workers introduced, at some specific sites, an unnatural fluorine-containing aminoacid and a nitroxide spin-label into a multidomain protein known to exist in different conformations. Measurements of F PRE allowed to determine the conformation under different conditions. Suzuki et used another fluorine-containing amino acid, inserted into different parts of a membrane-active peptide, as a local dynamics probe. They measured F transverse relaxation to examine changes in the mobility in different regions of the peptide upon binding to a lipid bilayer. 

NMRrelaxation and diffusion experiments provide important insights into both the internal molecular dynamics and the overall hydrodynamic behavior of unfolded and partly folded states. Local variations in backbone dynamics are correlated with propensities for local compaction of the polypeptide chain that results in constriction of backbone motions (Eliezer et al., 1998, 2000). This can occur through formation of... 

Solid state 2H NMR parameters are almost exclusively governed by the quadrupole interaction with the electric field gradient (EFG) tensor at the deuteron site.1 8 The EFG is entirely intramolecular in nature. Thus molecular order and mobility are monitored through the orientation of individual C-2H bond directions. Therefore, 2H NMR is a powerful technique for studying local molecular motions. It enables us to discriminate different types of motions and their correlation times over a wide frequency range. Dynamics of numerous polymers has been examined by solid state 2H NMR.1 3,7,9 Dynamic information on polypeptides by NMR is however limited,10 26 although the main-chain secondary structures of polypeptides in the solid have been extensively evaluated by 13C and 15N CP/MAS NMR.27,28... 

As discussed for N-myristoylation and S-prenylation, even S-acylation of proteins with a fatty acid which in the vast majority of cases is the C16 0 palmitic acid, plays a fundamental role in the cellular signal-transduction process (Table l). 2-5 14 While N-myristoylation and S-prenylation are permanent protein modifications due to the amide- and sulfide-type linkage, the thioester bond between palmitic acid and the peptide chain is rather labile and palmi-toylation is referred to as a dynamic modification. 64 This reversibility plays a crucial role in the modulation of protein functions since the presence or absence of a palmitoyl chain can determine the membrane localization of the protein and can also be used to regulate the interactions of these proteins with other proteins. Furthermore, a unique consensus sequence for protein palmitoylation has not been found, in contrast to the strict consensus sequences required for N-myristoylation and S-prenylation. Palmitoylation can occur at N- or C-terminal parts of the polypeptide chain depending on the protein family and often coexists with other types of lipidation (see Section 6.4.1.4). Given the diversity of protein sequences... 

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