Fig. 4: Photochemical cycles proposed for UV-excited L-cystine (1, blue) in aqueous solution. | Nature Communications

Fig. 4: Photochemical cycles proposed for UV-excited L-cystine (1, blue) in aqueous solution.

From: UV photochemistry of the L-cystine disulfide bridge in aqueous solution investigated by femtosecond X-ray absorption spectroscopy

Fig. 4

Upon illumination with 267-nm light, the S-S bond in 1 is cleaved homolytically yielding two L-cysteinylthiyl radicals (2, orange). Geminate recombination facilitates C-S bond cleavage to form the L-cysteinylperthiyl radical (3, purple) as a secondary reaction from the parent in a vibrationally excited state (VES). Alternatively, 1 is reformed by intramolecular energy relaxation or by recombination of the perthiyl and carbonyl radicals.

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