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ULTRAVIOLET INACTIVATION OF PAPAIN *
Author(s) -
Baugher J. F.,
Grossweiner L. I.
Publication year - 1975
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1975.tb06731.x
Subject(s) - chemistry , photochemistry , adduct , papain , flash photolysis , tryptophan , quantum yield , radical , organic chemistry , kinetics , amino acid , biochemistry , reaction rate constant , enzyme , fluorescence , quantum mechanics , physics
— Flash photolysis transient spectra (Λ > 250 nm) of aqueous papain show that the initial products are the neutral tryptophan radical Tip (Λ max 510 nm), the tryptophan triplet state 3 Trp (Λ m ., 460nm), the disulfide bridge electron adduct –ṠS ‐ — (Λ max 420nm) and the hydrated electron e aq ‐ . The –ṠS ‐ – yield was not altered by nitrous oxide or air, indicating that the formation of this product does not involve electrons in the external medium. The original papain preparation was activated by irradiating under nitrogen. The action spectrum supports previous work attributing the low initial activity to blocking of cysteinyl site 25 with a mixed disulfide. Flash lamp irradiation in nitrogen led to activation at low starting activities and inactivation at higher starting activities, while only inactivation at the same quantum yield was observed with air saturation. The results are consistent with photoionization of an essential tryptophyl residue as the key inactivating step.