Fig. 2. Partially allowed (grey) and allowed (black) torsion angles of the flanking amino acid residues (i+1 and i+2) about non-N-methylated and singly N-methylated peptide bonds. (A) Ac-AaAA-NH2 (absence of pA1,3 and pA1,2 strain); (B) Ac-AG(NMe)AA-NH2 (only pA1,2 strain); (C) Ac-Aa(NMe)GA-NH2 (only pA1,3 strain); (D) Ac-Aa(NMe)AA-NH2 (both pA1,3 and pA1,2 strain).
