Tuning Self-Assembled Nanostructures Through Enzymatic\nDegradation of a Peptide Amphiphile

Abstract

The enzymatic cleavage\nof a peptide amphiphile (PA) is investigated.\nThe self-assembly of the cleaved products is distinct from that of\nthe PA substrate. The PA C₁₆-KKFFVLK is cleaved by α-chymotrypsin\nat two sites leading to products C₁₆-KKF with FVLK and\nC₁₆-KKFF with VLK. The PA C₁₆-KKFFVLK forms\nnanotubes and helical ribbons at room temperature. Both PAs C₁₆-KKF and C₁₆-KKFF corresponding to cleavage products\ninstead self-assemble into 5–6 nm diameter spherical micelles,\nwhile peptides FVLK and VLK do not adopt well-defined aggregate structures.\nThe secondary structures of the PAs and peptides are examined by FTIR\nand circular dichroism spectroscopy and X-ray diffraction. Only C₁₆-KKFFVLK shows substantial β-sheet secondary structure,\nconsistent with its self-assembly into extended aggregates, based\non PA layers containing hydrogen-bonded peptide headgroups. This PA\nalso exhibits a thermoreversible transition to twisted tapes on heating.