Study on β-sheet packing, stabilized by aromatic interactions in a tri-peptide crystal

Abstract

Abstract The role of unconventional aromatic interactions in the β-sheet packing, inside the crystal, has been highlighted. Crystal structure of terminally blocked tri-peptide, Z-L-Ala-L-Ala-L-Leu-pNA has been determined. There are four different conformers of tri-peptide inside the unit-cell, in space group P1. All the four independent molecules are described by semi-extended backbone conformations which form an anti-parallel β-sheet. The inter β-sheet packing is predominantly stabilized by C—H…π and π…π interactions. In π…π interactions, the center-to-center distance between aromatic rings varies from 3.8 Å to 4.6 Å while the closest distance of approach ranges from 3.4 Å to 3.8 Å. The associations of aromatic-aromatic rings are described by either face-to-face or inclined arrangements.