Phenol coupling initiated by one-electron oxidation of tyrosine units in peptides and histone.
AffiliationUniversitat Freiburg, Institut fur Biophysik und Strahlenbiologie, ALbertstrasse 23, D-7800 Freiburg, FR Germany
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AbstractPhenoxyl radicals generated pulse radiolytically by the reaction of N.3 with Gly-Tyr decay biomolecularly (2k = 4.7 X 10(8)M-1 s-1) with efficient formation of 2,2'-dimers, which enolize rapidly (k = 2.7 X 10(4) s-1) to produce the 2,2'-biphenolic product. The build-up of the characteristic 2,2'-biphenol fluorescence (400 nm) and absorption also indicated a delayed (k = 80 s-1) process, probably involving the phenoxyl <-> phenoxy-quinol equilibrium. About 60 per cent of the Gly-Tyr phenoxyls were found to dimerize to the 2,2'-biphenol, and a similarly efficient 2,2'-coupling seems to occur with other tyrosyls, such as Lys-Tyr-Lys and histone. gamma-Radiolysis was applied to estimate relative yields of formation of 2,2'-biphenols under various conditions. Dimerization is almost completely inhibited by cysteine or oxygen, consistent with phenoxyl 'repair' by cysteine or O-.2; disproportionation of O-.2 with SOD prevents repair. The phenol 2,2'-coupling is less efficient for .OH- and inefficient for e-aq-initiation.
CitationPhenol coupling initiated by one-electron oxidation of tyrosine units in peptides and histone. 1983, 44 (2):183-96 Int J Radiat Biol Relat Stud Phys Chem Med
JournalInternational Journal of Radiation Biology and Related Studies in Physics, Chemistry, and Medicine
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