Reactivity of OH with tyrosine in aqueous solution studied by pulse radiolysis

Journal Article · Thu May 10 04:00:00 EDT 1984 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j150654a030· OSTI ID:6683967

Solar, S; Solar, W; Getoff, N

The specific OH attack on various sites of the tyrosine molecule in neutral aqueous solutions (pH 6-8), saturated with N/sub 2/O, has been investigated. The main process (approx. 50%) is the formation of ortho-directed OH adduct (R/sub 1/) with K = (7.0 +/-0.5) x 10/sup 9/ dm/sup 3/ mol/sup -1/s/sup -1/ (lambda/sub max/ = 330 nm, epsilon/sub 330/ = 300 +/- 30 m/sup 2/ mol/sup -1/), which decays by water elimination according to a first-order reaction (k' = (1.8 +/- 0.2) x 10/sup 4/ s/sup -1/) under formation of phenoxyl radical, as well as by second order with 2k = (3.0 +/- 1.0) x 10/sup 8/ dm/sup 3/ mol/sup -1/s/sup -1/. The phenoxyl radical is additionally formed as a primary product (approx. 5%) with k = (6.0 +/- 1.0) x 10/sup 8/ dm/sup 3/ mol/sup -1/s/sup -1/. It possesses two absorption maxima, 260 nm (epsilon/sub 260/ = 600 +/- 50 m/sup 2/ mol/sup -1/) and 405 nm (epsilon/3$/sub 05/ = 260 +/- 20 m/sup 2/ mol/sup -1/), and decays with 2k = (4.0 +/- 1.0) x 10/sup 8/ dm/sup 3/ mol/sup -1/ s/sup -1/). The meta isomer of the OH adducts (R/sub 2/) is formed to approx. 35% with k = (5.0 +/- 0.4) x 10/sup 9/ dm/sup 3/ mol/sup -1/s/sup -1/, having two absorption maxima at 305 nm (epsilon/sub 305/ = 280 +/- 30 m/sup 2/ mol/sup -1/) and 540 nm (epsilon/sub 540/ = 23 +/- 3 m/sup 2/ mol/sup -1/), and disappears with 2k = (2.0 +/- 0.5) x 10/sup 9/ dm/sup 3/ mol/sup -1/ s/sup -1/. The rest of approx. 10% OH radicals attack most probably the para and to a small extent ipso positions of the phenol ring under formation of the corresponding adducts. The H abstraction from the alanine moiety cannot by excluded. 26 references, 5 figures, 3 tables.

• Research Organization: Universitaet Wien, Austria
• OSTI ID: 6683967
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 88:10; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400600* -- Radiation Chemistry
ABSORPTION SPECTRA
AMINO ACIDS
AQUEOUS SOLUTIONS
CARBOXYLIC ACIDS
CHALCOGENIDES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
DATA
DATA ANALYSIS
DECOMPOSITION
DISPERSIONS
EXPERIMENTAL DATA
HYDROGEN COMPOUNDS
HYDROXY ACIDS
HYDROXYL RADICALS
INFORMATION
IRRADIATION
KINETICS
MIXTURES
NITROGEN COMPOUNDS
NITROGEN OXIDES
NITROUS OXIDE
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PH VALUE
PULSED IRRADIATION
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
RADIOLYSIS
REACTION KINETICS
SOLUTIONS
SPECTRA
TYROSINE
WATER