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Determining the nanostructure and main axis of gly-his-gly fibrils using the amide I' bands in FTIR, VCD, and Raman spectra
Journal article   Open access   Peer reviewed

Determining the nanostructure and main axis of gly-his-gly fibrils using the amide I' bands in FTIR, VCD, and Raman spectra

Nichole O'Neill, Thamires A. Lima, Fabio Furlan Ferreira, Nicolas J. Alvarez and Reinhard Schweitzer-Stenner
Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, v 306, pp 123584-123584
05 Feb 2024
PMID: 37956526
url
https://doi.org/10.1016/j.saa.2023.123584View
Accepted (AM)Open Access (Publisher-Specific) Open

Abstract

Science & Technology Spectroscopy Technology
The zwitterionic tripeptide glycyl-histidine-glycine (GHG) has been shown to self-assemble into visible crystalline fibrils that form a gel-supporting network with a very high storage modulus. Here we elaborate on the theory and experimental setup behind our novel approach employed to determining the main fibril axis for these gel-forming fibrils by simulating the amide I band profile for infrared absorption (IR), vibrational circular dichroism (VCD), and visible Raman scattering. We also highlight that combining these three vibrational spectroscopies can help in validating structures that are solved using powder x-ray diffraction analysis (PXRD). The PXRD analysis yielded a GHG fibril unit cell with P21 symmetry containing two peptide monomers and two water molecules. The monomers adopt a conformation reminiscent of the distorted polyproline II conformation obtained for tri-lysine in aqueous solution. Stabilization occurs primarily through peptide-peptide intermolecular hydrogen bond interactions, while the role of water in peptide hydration is minimal. The comparison of simulated and experimental amide I' band profiles suggests that the xz plane of the crystal unit cell is being predominantly probed in the experimental IR and VCD spectra, with the x axis of the unit cell pointing in the direction of the main fibril axis. The monomer peptide in the unit cell interacts with six adjacent peptides forming hydrophobic channels by edge-to-face and parallel displaced pi pi stacking in they direction. These cores are further stabilized by a plethora of intermolecular interactions in the x and z directions. Our result suggests that the hydrophobic xz-surfaces would be a good target for the adsorption of hydrophobic drugs.

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Web of Science research areas
Spectroscopy
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