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

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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].