Versatility in self-assembly and morphology of non-coded anthranilic acid and phenylglycine based dipeptide stereoisomers

Beauty in the self-assembly patterns of isomeric dipeptides of Boc-Ant- l -Phg-OMe ( 1 ) bearing two rigid, unnatural amino acids (Ant: anthranilic acid, Phg: phenylglycine) is demonstrated. Additionally, self-assembly and morphological variation by the incorporation of a d -amino acid, Boc-Ant- d -Phg-OMe ( 2 ), and corresponding reversed sequences of both peptides, Boc- l -Phg-Ant-OMe ( 3 ) and Boc- d -Phg-Ant-OMe ( 4 ), respectively, are explored. FT-IR study indicated the presence of conformational heterogeneity in the reverse peptides. SC-XRD suggested that 1 and 2 contain helical and β sheet-like layer architectures, respectively, whereas 3 and 4 exhibited different kinds of helical structures, sheet-like layer architectures, and molecular channels. Optical microscopy, FESEM, FETEM, and AFM images suggested that both C-terminal l - and d -Phg containing peptides ( 1 and 2 ) self-assembled to form a vesicular morphology and their reversed sequences, i.e. , N-terminal l - and d -Phg containing peptides ( 3 and 4 ), displayed a well-organized rod-like fiber structure. TGA analysis revealed that the obtained supramolecular structures have significant thermal stability. Molecular self-assembly and morphology of non-coded anthranilic acid and l / d -phenylglycine containing dipeptides have been investigated. Interestingly, significant morphological changes were observed just by reversing the peptide sequence.