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。用X射线晶体学方法鉴定了光解产物为{（CH_3）_2As^（V）（OH）_2}+{（CH_3）_2As^（V）O（OH）}_2][I_3]。（CH_3）_2As^（III）I在脱气甲醇中的激光闪光光解产生了一个中心在560 nm附近的宽峰的二甲基胂自由基（CH_3）_2As^（III）的瞬态光谱。砷自由基（CH_3）_2As^（III）的衰变符合二级动力学，生成（CH_3）_2As（III）^I。在氧气存在下，（CH_3）_2As^（III）与氧气反应生成过氧自由基[（CH_3）_2As^（III）（O_2）]，双分子速率常数为2.0 × 10_9 M_-1 s_-1。在λ> 500 nm波长范围内具有弱而宽吸收的过氧自由基按照一级动力学衰变，速率常数为5.0 x 10_5 s_-1。结果表明，过氧自由基单分子地转化为（CH_3）_2As^（V）（O）O，最终形成产物{（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].