Molecular mechanics study of the β‐spiral conformations of the Phe⁴, Tyr⁴, and Trp⁴ analogs of elastomeric poly(Val¹–Pro²–Gly³–Val⁴–Gly⁵)

The elastin‐derived polypentapeptide, poly(VPGVG), and analogs are becoming model systems for protein as well as forming a new class of biomaterials. The β‐spiral of poly(VPGVG) represents a new family of molecular structures in fibrous proteins. In particular for our interests here, aromatic amino acid residue substitutions at position four of poly(VPGVG) give rise to new polypeptides with interesting properties of increased elastic modulus, pressure sensitivity, etc. Molecular mechanics computations were carried out to answer the question, can the polypeptides with Phe, Tyr, and Trp substitution at position four of poly(VPGVG) form a β‐spiral structure like poly(VPGVG)? Employed in this study was a combination of conformational search using ECEPP/2 and the build‐up strategy and of molecular dynamics calculations using CHARMm. The results indicate that the VPGX Type II β‐turn structure appears to be the most prominent secondary structural feature for the three aromatic residues containing polypentapeptides, although there is more evidence for VPGFG and VPGVG to assume the VPGVG‐type structure than for VPGWG to do so. The study also shows that the aromatic side chains do not interrupt the β‐spiral structure, even in the case of tryptophan.