Marked difference in self-assembly, morphology, and cell viability of positional isomeric dipeptides generated by reversal of sequence

In this study two positional isomeric dipeptides Boc–m-ABA–Aib–OMe (1) and Boc–Aib–m-ABA–OMe (2) synthesized by reversal of the positions of two rigid amino acids (m-ABA: m-aminobenzoic acid, Aib: α-aminoisobutyric acid) showed marked difference in morphology under the same environmental conditions. Investigation of single crystal structures reveals the difference in crystal packing and higher order self-assembly pattern for both the isomeric peptides, which might be the responsible factor for their different morphological patterns. Moreover, these isomeric dipeptides have produced different cellular viability effects towards normal bone cells. These two peptides would have utilities in the model study of isomeric peptides/proteins, where morphological difference under identical conditions brings changes in their individual bio-activities and where the reversal of sequence causes different cellular viability and generates health hazard.