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KINETICS OF 4‐THIOURIDYLATE‐SENSITIZED PHOTOINACTIVATION OF RIBONUCLEASE A
Author(s) -
Sawada Fumio
Publication year - 1974
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.1751-1097.1974.tb06614.x
Subject(s) - ribonuclease , kinetics , chemistry , quantum yield , reaction rate constant , photosensitizer , nucleotide , rnase p , activation energy , yield (engineering) , ribonuclease t1 , action spectrum , photochemistry , stereochemistry , fluorescence , biochemistry , rna , organic chemistry , materials science , physics , quantum mechanics , metallurgy , gene
—An action spectrum for the inactivation of ribonuclease A photosensitized with 4‐thiouridylic acid follows the shape of the absorption spectrum of an RNase‐thiouridylate complex or of the unbound nucleotide. The quantum yield is 3.3 times 10 ‐3 . Statistical analysis of the data suggests that only the bound nucleotide participates in the photoinactivation. An Arrhenius plot for the first‐order rate constants of inactivation gives a straight line in the range 0–40d̀C and an apparent activation energy of photoinactivation of 5.7 kcal/mol. The 4‐thiouridylate‐sensitized photoinactivation of ribonuclease A is regarded as a kind of photodynamic action in which the substrate analogue plays the role of photosensitizer.