Determination of ultimate substances on arsenic carcinogenesis and in vivo formation mechanisms of their substances

在甲醇溶液中进行了（CH_3）_2As^<(III)>I的连续光解和激光光解研究。经x射线晶体学鉴定，连续光解得到的光产物为{(CH_3)_2As^(V)(OH)_2}+{(CH_3)_2As^(V)O(OH)}_2][I_3]。激光在脱气甲醇中光解（CH_3）_2As^(III)I得到了二甲基larsine自由基（CH_3）_2As^（III）的瞬态光谱，其宽峰中心在560nm左右。砷自由基（CH_3）_2As^（III）按照二级动力学衰变再生（CH_3）_2As(III)^I。在氧存在下，（CH_3）_2As^（III）与氧反应生成过氧自由基[(CH_3)_2As^(III)(O_2)]，其双分子速率常数为2.0 × 10_9 m_1 s_1。过氧自由基在λ> ~ 500 nm波长区具有弱而宽的吸收，其衰变符合一级动力学，速率常数为5.0 × 10_5 s_1。结果表明，过氧自由基单分子转化为（CH_3）_2As^(V)(O)O，最终生成产物{(CH_3)_2As^(V)(OH)_2}+{(CH_3)_2As^(V)O(OH)}_2][I_3]。

Continuous and laser photolysis studies of (CH_3)_2As^<(III)>I were carried out in methanol solutions. The photoproduct obtained with the continuous photolysis of the aerated solutions was identified as {(CH_3)_2As^(V)(OH)_2}+{(CH_3)_2As^(V)O(OH)}_2][I_3] by X-ray crystallography. The laser flash photolysis of (CH_3)_2As^(III)I in a degassed methanol gives a transient spectrum of dimethylarsine radical, (CH_3)_2As^(III), with a broad peak centered around 560 nm. The arsinous radical, (CH_3)_2As^(III), decays according to second order kinetics to regenerate (CH_3)_2As(III)^I. In the presence of oxygen, (CH_3)_2As^(III) reacts with oxygen to yield the peroxy radicals, [(CH_3)_2As^(III)(O_2)] with the bimolecular rate constant, 2.0 x 10_9 M_-1 s_-1. The peroxy radical having weak and broad absorption in the wavelength region λ> 500 nm decays according to first order kinetics with a rate constant 5.0 x 10_5 s_-1. It is suggested that the peroxy radical unimolecularly converts to (CH_3)_2As^(V)(O)O, which eventually turns to the product {(CH_3)_2As^(V)(OH)_2}+{(CH_3)_2As^(V)O(OH)}_2][I_3].