Conformational properties of disulfide bridges. Part 3. An estimation of structural flexibility from a theoretical study of diethyl disulfide

Abstract

The conformational flexibility of disulfide bridges is discussed on the basis of theoretical ab initio calculations with diethyl disulfide as a model molecule. The equilibrium structure of various disulfide bridge conformations can be stretched or compressed over a surprisingly wide range of C^α⋯ C^α separations with a comparatively small energy penalty. This substantial flexibility is essential when disulfide bridges adapt to the surrounding peptide chains in the ternary structure of proteins. The total combined range for C^α⋯ C^α separations in all disulfide conformations is ca. 4.5 Å(from 3.4 to 6.9 Å), which is superior to the normal ranges for other hypothetical covalent links between polypeptide chains.