Electron-transfer reactions of tryptophan and tyrosine derivatives

Journal Article · Wed Apr 23 23:00:00 EST 1986 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100400a039· OSTI ID:5682335

Jovanovic, S V; Harriman, A; Simic, M G

Oxidation of tryptophan, tyrosine, and derivatives by oxidizing radicals was studied by pulse radiolysis in aqueous solutions at 20 /sup 0/C. Rate constants for the oxidation of tryptophan derivatives with .N/sub 3/ and Br/sub 2//sup -/. radicals vary from 8 x 10/sup 8/ to 4.8 and 10/sup 9/ M/sup -1/ s/sup -1/ and oxidation goes to completion; no pH dependence was observed. Oxidation rate constants for tyrosine derivatives increase upon deprotonation of the phenolic residue at higher pH. Redox potentials for the indolyl and phenoxyl radicals were derived from the measured equilibrium constants by using p-methoxyphenol (E/sub 7.5/ = 0.6 and E/sub 13/ = 0.4 V), bisulfite (E/sub 3/ = 0.84 V), and guanosine (E/sub 7/ = 0.91 V) redox couples as reference systems. Redox potentials of tryptophan derivatives were found to be in dependent on the nature of the side chain and higher than the redox potentials of tryptophan derivatives. Electron transfer from tyrosine to tryptophyl radical was found to be slow in neutral media and is suggested to proceed via multiple steps, one of which is proton transfer from tyrosine to tryptophyl radical followed by electron transfer. 26 references, 2 figures, 4 tables.

• Research Organization: National Bureau of Standards, Gaithersburg, MD
• OSTI ID: 5682335
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 90:9; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
400600 -- Radiation Chemistry
AMINO ACIDS
AROMATICS
AZAARENES
AZOLES
CARBOXYLIC ACIDS
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
DATA
DECOMPOSITION
ELECTRON TRANSFER
EXPERIMENTAL DATA
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROXY ACIDS
INDOLES
INFORMATION
KINETICS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDATION
PULSE TECHNIQUES
PYRROLES
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIOLYSIS
REACTION INTERMEDIATES
REACTION KINETICS
TRYPTOPHAN
TYROSINE