Conformational transition Subject

There are two major ways of control. One mechanism involves reversible covalent modifications, such as phosphorylation dephosphorylation, the other requires conformational transitions by binding an allosteric ligand or regulator protein. It follows an example of regulation of an enzyme, of which the activity is subject to control by both mechanisms, then we compare the regulation of an enzyme with regulation of components of cellular signalling pathways, of which many have no enzymic activity. 

The details of these sampling procedures that allow one to focus on the aspect of the problem of interest are the subject of a review by Beveridge (133). Application of this approach to determining conformational transitions in model peptides (137,139,140)are exemplified in the work of Elber s group on helix-coil (85, 86,141), the Brooks group on tum-coil (142-146), and Huston and Marshall and Smythe et al. (147,148)on helical transitions in peptides. 

In addition to their use in the in situ induction of conformational transitions, switch-peptides (O-acyl isopeptides) may serve as alternative solubilizing technique in peptide synthesis [207-214]. The elaboration of these concepts, notably the rational design of dynamic pharmacophores as new type of therapeutically useful compounds, is the subject of our current research. 

Heat-induced conformational transitions of globular proteins have been the subject of an enormous amount of work from both the theoretical and the experimental points of view. Elaborated quantitative... 

The preceding considerations, together with others drawn from the results of model building studies and from an analysis of the substrate specificity of pancreatic RNase (v. infra) are discussed more fully elsewhere all are consistent with the following formulations in contrast to normal nucleotides (1) formycin residues in polynucleotides are subject to conformational transitions which tcike place at the glycosyl bond. (2) The formycin nucleotides are (a) anti in ordered double-stranded structures of the Watson-Crick type (b) syn in neutral poly F and (c) probably a mixture of syn and anti in single stranded copolymers. 

The conformational behavior of polymer and polyelectrolyte chains in dilute solutions is an interesting and practically important aspect and has been a subject of numerous studies since early 1950s. While the dynamics of polymers can be studied more or less directly by time-resolved depolarization measurements, the conformations and conformational transitions are studied indirectly via changes in the reorientation correlation times. However, because the correlation times depend sensitively on the chain conformations and the changes accompanying the structural transitimis are usually quite pronounced, the conclusions concerning the conformational behavior are reliable in the overwhelming majority of cases. 

While the conformational distribution in flexible chain molecules has been a subject of intensive theoretical and experimental study ever since Kuhn s pioneering workl, the dynamics of conformational transition have become only much more recently a subject of experimental study. 

The master equation is derived by asymptotic analysis of the multidimensional diffusion equation in the torsional angles subjected to the configurational potential, with the coupling between the variables explicitly taken into account. Molecular definitions of the kinetic rates for the conformational transitions occurring at each segment of the chain are obtained in terms of the dynamic and hydrodynamic properties of the system. The following physical quantities enter in the specification of the problem ... 

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