Role of Side-Chain and Chirality of the Amino acids on the Supramolecular Assemblies of Dipeptides
Sayanta Roy, Rajat Subhra Giri, Gobinda Dolai, Bhubaneswar Mandal
Journal of Molecular Structure
The supramolecular self-association of alternating L/L and L/D amino acid-containing dipeptides, Boc-L-Ile-L-Phe-OMe (1), Boc-L-Ile-D-Phe-OMe (2), Boc-L-Ile-L-Phg-OMe (3, Phg = phenylglycine), and Boc-L-Ile-D-Phg-OMe (4) have been investigated. The presence of extra methylene (-CH2-) group on the side-chain of C-terminal Phe of 1 causes a significant deviation of molecular arrangements from that of 3. While the molecules in 1 self-assemble to form a single helix-like architecture, the molecules in 3 self-associate around a water molecule to form a cylinder-like structure in the crystalline state. Alternatively, the observed supramolecular arrangements of 2 and 4 are similar, but deviate from that of 1 and 3, due to chirality difference. Peptides 2 and 4 exhibit a discontinued double helix-like structure in the crystalline state. While 1 and 3 self-associate to form helical ribbon-like and nano tube-like structures, respectively, both 2 and 4 form nano rod-like structures in solution.
Circular dichroism, Secondary structure, Biochemistry