Supramolecular beta-sheet and nanofibril formation by self-assembling tripeptides containing an N-terminally located gamma-aminobutyric acid residue

Ray, S., Drew, M.G.B., Das, A.K. and Banerjee, A. (2006) Supramolecular beta-sheet and nanofibril formation by self-assembling tripeptides containing an N-terminally located gamma-aminobutyric acid residue. Supramolecular Chemistry, 18 (5). pp. 455-464. ISSN 1061-0278 doi: 10.1080/10610270600677033

Abstract/Summary

Three terminally protected tripeptides Boc-gamma-Abu-Val-Leu-OMe 1, Boc-gamma-Abu-Leu-Phe-OMe 2 and Boc-gamma-Abu-Val-Tyr-OMe 3 (gamma-Abu = gamma-aminobutyric acid) each containing an N-terminally positioned gamma-aminobutyric acid residue have been synthesized, purified and studied. FT-IR studies of all these peptides revealed that these peptides form intermolecularly hydrogen bonded supramolecular beta-sheet structures. Peptides 1, 2 and 3 adopt extended backbone beta-strand molecular structures in crystals. Crystal packing of all these peptides demonstrates that these beta-strand structures self-assemble to form intermolecularly H-bonded parallel beta-sheet structures. Peptide 3 uses a side chain tyrosyl -OH group as an additional hydrogen bonding functionality in addition to the backbone CONH groups to pack in crystals. Transmission electron microscopic studies of all peptides indicate that they self-assemble to form nanofibrillar structures of an average diameter of 65 nm. These peptide fibrils exhibit amyloid-like behavior as they bind to a physiological dye Congo red and show a characteristic green-gold birefringence under polarizing microscope.