A microscopic view of a helical poly(γ‐peptide): Molecular dynamics simulations of a 20‐residue un‐ionized poly(γ‐D‐glutamic acid) in water

We present a molecular dynamics study of the helical conformation of the naturally occurring poly(γ‐D ‐glutamic acid) in the un‐ionized state. The study was conducted in both aqueous solution and gas‐phase considering a 20 residue polypeptide. The results indicated that the left‐handed helix with 19‐membered ring hydrogen bonds set between the CO of the amide group i and the NH of amide group i + 3 is very stable in aqueous solution. This conformation was recently proposed for this poly(γ‐amino acid) from a conformational search study. A detailed picture of the most relevant structural details of the helical conformation of poly(γ‐D ‐glutamic acid) is provided.