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Is a Cross-β-Sheet Structure of Low Molecular Weight Peptides Necessary for the Formation of Fibrils and Peptide Hydrogels?

Abstract

Short peptides have emerged as versatile building blocks for supramolecular structures and hydrogels. The presence of aromatic amino acid residues and/or aromatic end groups is generally considered to be a prerequisite for initiating aggregation of short peptides into nanotubes or cross β-sheet type fibrils. However, the cationic GAG tripeptide surprisingly violates these rules. Specifically, in water/ethanol mixtures, GAG peptides aggregate into very long crystalline fibrils at temperatures below 35°C where they eventually form a spanning network structure and, thus, a hydrogel. Two gel phases are formed in this network, and they differ substantially in chirality and thickness of the underlying fibrils, their rheological parameters, and the kinetics of oligomerization, fibrilization, and gel formation. The spectroscopic data strongly suggests that the observed fibrils do not exhibit canonical cross β-sheet structures and are indicative of a yet unknown secondary conformation. To complement our unusual experimental observations in this perspective article, we performed large-scale DFT calculations to probe the geometry and spectroscopic properties of these GAG oligomers. Most importantly, our experimental and computational results yield rather unconventional structures that are not reminiscent of classical cross β-sheet structures, and we give two extremely likely candidates for oligomer structures that are consistent with experimental amide I' profiles in IR and vibrational circular dichroism (VCD) spectra of the two gel phases.

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Supplementary files

Publication details

The article was received on 30 Jan 2018, accepted on 17 Apr 2018 and first published on 17 Apr 2018


Article type: Perspective
DOI: 10.1039/C8CP00691A
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    Is a Cross-β-Sheet Structure of Low Molecular Weight Peptides Necessary for the Formation of Fibrils and Peptide Hydrogels?

    N. Ilawe, R. Schweitzer-Stenner, D. DiGuiseppi and B. Wong, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C8CP00691A

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