Reactions of dichloride anion radicals with pyrimidine and its derivatives.
Rate constants for the reactions of dichloride anion radicals with pyrimidine and its derivatives were determined by a conventional flash photolysis. Kinetic treatment was carried out by assuming that second-order self decay of the anion radicals and the reaction with a substrate proceed simultaneously. Values of the rate constants were found within 1.1 × 107 to 4.1 × 109 M-1 s-1; the lowest reactivity was observed for pyrimidine and the highest for 2, 4, 6triaminopyrimidine. Comparison of the rate constants with those for hydroxyl radicals suggests that the dichloride anion radicals undergo a different reaction with pyrimidine bases from that of the hydroxyl radicals. A transient absorption due to an intermediate produced in the reaction with the anion radicals was observed for 5-aminouracil. This is only a case where relatively long-lived absorption was observed. The absorption was used to determine the rate constants for the reactions with the anion radicals.
ESR study of DNA base cation radicals produced by attack of oxidizing radicals
ESR investigations of ..gamma..-irradiated aqueous glasses (8 M NaClO/sub 4/, 12 M LiCl) containing DNA bases and analogues show that oxidizing species produced in the glasses (hydroxyl radicals and Cl/sub 2//sup -/) at 77 K attack a number of the bases and their analogues after warming to produce ..pi..-cation radicals. Compounds which produce ..pi.. cations include thymine, uracil, 3-methyluracil, 6-methyluracil, orotic acid, isoorotic acid, guanine, and adenine. Compounds which are not found to produce ..pi.. cations are 1-methylthymine, thymidine, and 1-methyluracil. The overall reaction for formation of the ..pi.. cations is as follows: base + OH.(Cl/sub 2//sup -/) ..-->.. OH/sup -/(2Cl/sup -/) + base cation. A pH and substituent dependence is also noted for the pyrimidines. At pHs where the nitrogen at position 1 is protonated, ..pi..-cation radicals are not formed. In addition, when there are substituents at position 1, ..pi.. cations are not found. Analysis of the ESR spectra of the DNA base ..pi.. cations for hyperfine splittings and g values were performed by aid of computer simulations. The analyses are in agreement with values found for several DNA base cations produced by photolysis and by direct ..gamma.. irradiation.
Selected specific rates of reactions of transients from water in aqueous solution. 1. Hydrated electron
Abstract : Rates of reaction of hydrated electrons with over 700 different organic and inorganic molecules, ions, and transients have been tabulated. Most of the data are derived from pulse radiolysis of aqueous solutions; results from photolysis and from steady-state radiolysis by completion kinetics are also included. (Author)