Journal of the American Chemical Society
Journal of the American Chemical Society
5 years ago

Purple Fibrils: A New Type of Protein Chromophore

Purple Fibrils: A New Type of Protein Chromophore
Vladimir Grigoryants, Maruda Shanmugasundaram, Tatiana Quiñones-Ruiz, Charles Scholes, Karina Ruiz-Esteves, Igor K. Lednev, Manuel F. Rosario-Alomar, Juan López-Garriga
A purple color is formed during the fibrillation of lysozyme, a well-studied protein lacking a prosthetic group. The application of Raman spectroscopy, electron paramagnetic resonance and UV–vis absorption spectroscopy indicates the formation of a sulfur∴π-bonded radical cation due to the methionine-phenylalanine interaction, which is consistent with a small molecule model reported in the literature. A purple chromophore with characteristic 550 nm absorption is formed due to a specific orientation of the sulfur-centered radical cation and a phenyl ring stabilized by the fibril framework. A specific fibril conformation and the resulting formation of the chromophore are controlled reversibly by varying the pH. This is the first known example of a side chain self-assembled chromophore formed due to protein aggregation.

Publisher URL: http://dx.doi.org/10.1021/jacs.7b03056

DOI: 10.1021/jacs.7b03056

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