Side-chain reorientations

Batchelder, L. S., Sullivan, C. E., Jelinski, L. W., and Torchia, D. A. (1982). Characterization of leucine side-chain reorientation in collagen fibrils by solid state 2H NMR. Proc. Natl. Acad. Sci. 79, 386—389. 

Modified HRP with maleic and citraconic anhydrides An enhanced thermostability of modified HRP with respect to native HRP was observed, and the changes were attributed to side chain reorientations of the aromatic residues of the enzyme [66]... 

HRP. The existence of conformational changes was confirmed by circular dichro-ism studies, and the enhanced thermostability of modified HRP was attributed to side chain reorientations of aromatic residues [66]. 

Fig. 7 The influenza virus A sialidase active site showing the five potential inhibitor binding subsites (with S5 containing the hydrophobic pocket formed by reorientation of the Glu276 side-chain), with oseltamivir carboxylate 18 placed in the active site...

Raloxifene is also anchored to the same three amino acids as estradiol by direct hydrogen bonds, but it also interacts with Asp 351. The final orientation of raloxifene within the binding pocket determines that its side chain displaces helix 12. Then, helix 12 becomes reoriented and cannot seal the pocket containing the ligand (MacGregor et al. 1998). The repositioned AF-2 region impairs the formation of transcription complex by coactivators, and the signal transduction is blocked. 

The non-collective motions include the rotational and translational self-diffusion of molecules as in normal liquids. Molecular reorientations under the influence of a potential of mean torque set up by the neighbours have been described by the small step rotational diffusion model.118 124 The roto-translational diffusion of molecules in uniaxial smectic phases has also been theoretically treated.125,126 This theory has only been tested by a spin relaxation study of a solute in a smectic phase.127 Translational self-diffusion (TD)29 is an intermolecular relaxation mechanism, and is important when proton is used to probe spin relaxation in LC. TD also enters indirectly in the treatment of spin relaxation by DF. Theories for TD in isotropic liquids and cubic solids128 130 have been extended to LC in the nematic (N),131 smectic A (SmA),132 and smectic B (SmB)133 phases. In addition to the overall motion of the molecule, internal bond rotations within the flexible chain(s) of a meso-genic molecule can also cause spin relaxation. The conformational transitions in the side chain are usually much faster than the rotational diffusive motion of the molecular core. 

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