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Forbidden Secondary Structures Found in Gel-Forming Fibrils of Glycylphenylalanylglycine
Journal article

Forbidden Secondary Structures Found in Gel-Forming Fibrils of Glycylphenylalanylglycine

Nichole O’Neill, Thamires A. Lima, Fabio Furlan Ferreira, Lavenia Thursch, Nicolas Alvarez and Reinhard Schweitzer-Stenner
The journal of physical chemistry. B, v 126(40), pp 8080-8093
13 Oct 2022

Abstract

B: Soft Matter, Fluid Interfaces, Colloids, Polymers, and Glassy Materials
The zwitterionic l-tripeptide glycylphenylalanylglycine self-assembles into very long crystalline fibrils in an aqueous solution, which causes the formation of an exceptionally strong gel phase (G′ ∼ 5 × 106 Pa). The Rietveld refinement analysis of its powder X-ray diffraction (PXRD) pattern reveals a unit cell with four peptides forming a P212121 space group and adopting an inverse polyproline II conformation, that is, a right-handed helical structure that occupies the “forbidden” region of the Ramachandran plot. This unusual structure is stabilized by a plethora of intermolecular interactions facilitated by the large number of different functional groups of the unblocked tripeptide. Comparisons of simulated and experimental Fourier transform infrared and vibrational circular dichroism (VCD) amide I′ profiles corroborate the PXRD structure. Our experimental setup reduces the sample to a quasi-two-dimensional network of fibrils. We exploited the influence of this reduced dimensionality on the amide I VCD to identify the main fibril axis. We demonstrate that PXRD, vibrational spectroscopy, and amide I simulations provide a powerful toolset for secondary structure and fibril axis determination.

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Collaboration types
Domestic collaboration
International collaboration
Web of Science research areas
Chemistry, Physical
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