Conformation-dependent properties

Stepto, R.F.T., Theoretical aspects of conformation-dependent properties. In Clarson, S.J. and Semiyen, J.A. (Eds.),. Siloxane Polymers, Polymer Science and Technology Series. PTR Prentice Hall, Englewood Cliffs, NJ, 1993, pp. 373-414. 

Teramoto, A. and Fujita, H. Conformation-dependent Properties of Synthetic Polypeptides in the Helix-Coil Transition Region. Vol. 18, pp. 65-149. 

The growing computahonal power available to researchers proves an invaluable tool to investigate the dynamic profile of molecules. Molecular dynamics (MD) and Monte Carlo (MC) simulahons have thus become pivotal techniques to explore the dynamic dimension of physicochemical properhes [1]. Furthermore, the powerful computational methods based in parhcular on MIFs [7-10] allow some physicochemical properhes to be computed for each conformer (e.g. virtual log P), suggesting that to the conformahonal space there must correspond a property space covering the ensemble of all possible conformer-dependent property values. 

Conformation-Dependent Properties of Synthetic Polypeptides in the Helix-Coil Transition Region... 

Any discussion of the conformation-dependent properties of macromolecular solutions must start with a consideration of the physical parameters required for quantitative description of the average conformation of the solute molecule in solution. As shown below, three parameters, N, s, and a, are necessary and sufficient for helix-forming homopolypeptides. Here N is the degree of polymerization of the polypeptide molecule, and s and tr have the meanings described in Chapter B. 

From the above discussion it is clear that the average conformation of a polypeptide in solution depends on both the chain length N and the co-operativity parameter a, even if the helical fraction is fixed. In particular, it has been shown that, when compared at the same fN and N, the average number of helical sequences, gN, becomes smaller as a is lowered. Thus for fixed fN and N there exist a variety of different interrupted helical conformations, depending on the magnitude of a. Figure 4 illustrates two typical examples of such conformations. This theoretical prediction makes a study of the conformation-dependent properties of synthetic polypeptides rather inviting. 

In order to check the flexibility of polypeptide helix predicted by these considerations, we may utilize various conformation-dependent properties. The most tangible way will be to examine the chain-length dependence of 1/2, which ought to be linear for a series of rigid rods of constant diameter. 

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