Photoactive proteins are exploited widely in nature and technology as photoreceptors. Photoactive yellow protein (PYP) is a prototypical signaling protein. In the first step of the photocycle of PYP, absorption of blue light triggers trans–cis isomerization of the chromophore covalently bound within the protein; this eventually results in the host Halorhodospira halophila bacterium moving away from potentially harmful light. Understanding how the interactions between the chromophore and the surrounding protein control the dynamics of the chromophore, and thus the protein function, is a major challenge in photochemistry and photobiology. In a previous study of a series of model PYP chromophores, we found that torsions around the C-C single bonds lowered the threshold for electron emission.1 Here, we investigate the role of the thioester link between the chromophore and the protein in controlling electron emission. Specifically, we employ anion photoelectron spectroscopy and quantum chemistry calculations to investigate the competition between electron emission and internal conversion back to the ground state in the model chromophore, the deprotonated para-coumaric acid anion, its methyl ester and its methyl thioester. (1) Mooney, C. R. S.; Parkes, M. A.; Iskra, A.; Fielding, H. H. Angew. Chemie Int. Ed. 2015, 54, 5646.

Using chemistry to control electron emission from the photoactive yellow protein chromophore

251st National Meeting (2016)

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