Nonadditivity in conformational entropy upon molecular rigidification reveals a universal mechanism affecting folding cooperativity.

ABSTRACT: Previously, we employed a Maxwell counting distance constraint model (McDCM) to describe α-helix formation in polypeptides. Unlike classical helix-coil transition theories, the folding mechanism derives from nonadditivity in conformational entropy caused by rigidification of molecular structure as intramolecular cross-linking interactions form along the backbone. For example, when a hydrogen bond forms within a flexible region, both energy and conformational entropy decrease. However, no conformational entropy is lost when the region is already rigid because atomic motions are not constrained further. Unlike classical zipper models, the same mechanism also describes a coil-to-β-hairpin transition. Special topological features of the helix and hairpin structures allow the McDCM to be solved

SUBMITTER: Vorov OK 

PROVIDER: S-EPMC3037720 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature