N and N+1 cap positional effects of (D) alanine in the 310 type helical model peptide Boc-(D)Glu-Ala-Ala-Lys-NHMe

Abstract

The N (Ala₂) and N+1(Ala₃) cap positional alanine in the 3₁₀ helical model peptide Boc-(D)Glu₁-Ala₂-Ala₃-Lys₄-NHMe, 2 is substituted with a (D)alanine. An NMR enquiry using solvents that promote appreciable ordering of peptide 2, against random conformation of the parent (L)Glu₁ peptide 1, establishes that D alanine partially disorders the type II’ turn templated 3₁₀ type helical fold and distorts it in a position dependent manner, more strongly from N cap position than from N+1 cap position.