Issue 46, 2021

Structure–mechanical property relationship of a pentapeptide crystal

Abstract

The structure–mechanical property relationship of a synthetic pentapeptide crystal containing coded and non-coded amino acids was presented. Pentapeptide 1 has two α-aminoisobutyric acid (Aib) residues at 2 and 4 positions and formed an orthorhombic crystal, with the space group P212121, which is sensitive to external stress and brittle in nature. From FE-SEM the crystal appears as a thick bundle of several fibers. The structural analysis of a crystal of pentapeptide 1 obtained in methanol–water confirmed the existence of an unusual secondary structure, a miniature (P)310/α-helix. The pentapeptide 1 molecules self-assemble by intermolecular N–H⋯O hydrogen bonds and form a supramolecular helical bundle structure which further assembles to form a supramolecular sheet-like structure along the crystallographic a and c directions. The intermolecular interaction energies (kJ mol−1) for pentapeptide 1 were calculated using the B3LYP/6-31G(d,p) dispersion corrected DFT model. Although the interaction energy is small, there is no sign of slippage due to the interdigitation of the Leu i-propyl, Boc t-butyl, and Phe side chains. As a result, the crystal is brittle in nature. Moreover, the quantitative nanoindentation technique reveals the moderate E and H values for the major face of this crystal, which is consistent with the presence of adequate van der Waals interactions and several hydrogen bonding interactions in the structure.

Graphical abstract: Structure–mechanical property relationship of a pentapeptide crystal

Supplementary files

Article information

Article type
Paper
Submitted
04 Kho 2021
Accepted
11 Nhl 2021
First published
12 Nhl 2021

CrystEngComm, 2021,23, 8093-8098

Structure–mechanical property relationship of a pentapeptide crystal

S. K. Nandi, S. Mondal, S. Mondal, M. Gumtya and D. Haldar, CrystEngComm, 2021, 23, 8093 DOI: 10.1039/D1CE00738F

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