Theoretical Study of a Nonpeptidic Polydisulfide α-Helix.

A carbon-sulfur molecule has been designed as a mimic of peptides. Density functional theory calculations showed that the oxidation of 10 moles of methanedithiol led to a polydisulfide oligomer, HS(CHSS)CHSH. The polydisulfide can adopt an α-helix type of secondary structure, where the chain is coiled. Unlike proteins, the S-S bonds in the polydisulfide function as secondary rather than tertiary structural elements. The helix contains 8 non-hydrogen atoms per turn, 2.7 Å methylenes per turn, a pitch distance of 8.6 Å, and a radius of 1.00 Å. The methylene sites could carry R group residues similar to amino acids.