16978-66-8Relevant articles and documents
Electrocatalytic oxidation of tyrosine by parallel rate-limiting proton transfer and multisite electron-proton transfer
Fecenko, Christine J.,Meyer, Thomas J.,Thorp, H. Holden
, p. 11020 - 11021 (2006)
The oxidation of the amino acids tyrosine and tryptophan by complexes based on M(bpy)33+ (M = Ru, Os) was studied by monitoring the cyclic voltammetry of the metal complex in the presence of the oxidizable amino acids. Addition of bo
Photoinduced Electron Transfer from Amino Acids and Proteins to 4-Nitroquinoline 1-Oxide in Aqueous Solutions
Seki, Hiroshi,Takematsu, Akiko,Arai, Shigeyoshi
, p. 176 - 179 (1987)
The reactions of the triplet state of 4-nitroquinoline 1-oxide (4NQO) with a series of amino acids and some proteins in aqueous solutions have been studied by using a laser flash technique.Only triptophan (TrpH) and tyrosine (TyrOH) among a series of amino acids quench the triplet 4NQO (TNQO) at a diffusion-controlled rate.Lysozyme, ribonuclease, and histone, which contain TrpH and/or TyrOH residues, had rate constants comparable to those of TrpH and TyrOH.The formation of the H adduct of 4NQO (4NQOH.), which may be produced by the reaction of 4NQO- with water, was confirmed from the transient absorption spectra for 4NQO solutions containing these quenchers.The transient absorption spectra observed for TrpH and TyrOH solutions elucidated the formation of the deprotonated forms of TrpH+ and TyrOH+ (Trp. and TyrO.) together with 4NQOH..The result demonstrates that the elctron transfer from TrpH or TyrOH to T4NQO occurs in the triplet quenching by TrpH or TyrOH.Since the almost same transient spectra as Trp. and TyrO. were observed for lysozyme and ribonuclease solutions, respectively, TrpH residues on lysozyme and TyrOH residues on ribonuclease are main quenching sites, where elctron transfer and deprotonation occur.The quantum yields of T4NQO, 4NQOH., Trp., and TyrO. produced by the excitation of the 4NQO solution containing TrpH or TyrOH with a 355-nm light pulse were determined to be 0.46, 0.47, 0.41, respectively.The result shows that the efficiency in electron transfer from TrpH or TyrOH to T4NQO is ca.90percent.For the reaction of T4NQO with methionine, arginine, histidine, lysozyme, or ribonuclease, the efficiency in electron transfer was also estimated to be nearly equal to that for the reaction with TrpH or TyrOH.
Reactivity of OH with Tyrosine in Aqueous Solution Studied by Pulse Radiolysis
Solar, S.,Solar, W.,Getoff, N.
, p. 2091 - 2095 (2007/10/02)
The specific OH attack on various sites of the tyrosine molecule in neutral aqueous solutions (pH 6-8), saturated with N2O, has been investigated.The main process (ca. 50percent) is the formation of ortho-directed OH adduct (R1) with k = (7.0 +/- 0.5)E9 dm3 mol-1 s-1 (λmax = 330 nm, ε330 = 300 +/- 30 m2 mol-1), which decays by water elimination according to a first-order reaction (k'= (1.8 +/- 0.2)E4 s-1) under formation of phenoxyl radical, as well as by second order with 2k = (3.0 +/- 1.0)E8 dm3 mol-1 s-1.The phenoxyl radical is additionally formed as a primary product (ca. 5percent) with k = (6.0 +/- 1.0)E8 dm3 mol-1 s-1.It possesses two absorption maxima, 260 nm (ε260 = 600 +/- 50 m2 mol-1) and 405 nm (ε405 = 260 +/-20 m2 mol-1), and decays with 2k = (4.0 +/- 1.0)E8 dm3 mol-1 s-1).The meta isomer of the OH adducts (R2) is formed to ca. 35percent with k = (5.0 +/- 0.4)E9 dm3 mol-1 s-1, having two absorption maxima at 305 nm (ε305 = 280 +/- 30 m2 mol-1) and 540 nm (ε540 = 23 +/- 3 m2 mol-1), and disappears with 2k = (2.0 +/- 0.5)E9 dm3 mol-1 s-1.The rest of ca. 10percent 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 be excluded.
