Effects of sulfoxide and sulfone sidechain-backbone hydrogen bonding on local conformations in peptide models

We examine peptide model systems designed to probe short-range N-HMIDLINE HORIZONTAL ELLIPSISO 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 S sidechain-backbone hydrogen bonding involving amino acid residues with sidechain sulfoxide or sulfone functional groups and its effects on local conformations. A strong 7-membered ring hydrogen bond of this type accompanies an intra-residue N-HMIDLINE HORIZONTAL ELLIPSISOC interaction and stabilizes an extended backbone conformation in preference to classical folded structures. Examination of peptide model systems with sidechain sulfoxide or sulfone functional groups has led to the discovery of a strong 7-membered ring N-H center dot center dot center dot OS sidechain-backbone hydrogen bond that stabilizes a C5 extended backbone conformation.