[Effect of antioxidants on photoaddition of 8-methoxypsoralen to thymine, double-helix DNA and photosensitized inactivation of Escherichia coli].

Effect of antioxidants--alpha-tocopherol and 2,6-di-tert-butyl-hydroxytoluene (BHT) on 2-methoxypsoralen (8-MOP) photoaddition was investigated. Spectrophotometric experiments have shown that under anaerobic conditions alpha-tocopherol inhibits photodimerization of 8-MOP and photoaddition of 8-MOP to thymine (in 80% ethanol solution). 50% inhibition is obtained at alpha-tocopherol concentrations of about 10(-5) M. The antioxidants (in concentrations from 10(-8) to 10(-4) M) displayed no effect on photoaddition of 8-MOP to double-stranded DNA in solution. The reactions of 8-MOP photoaddition to double-stranded DNA were registered by formation of fluorescent monoadducts and interstrand crosslinks. The antioxidants also did not inhibit 8-MOP-photosensitized inactivation of E. coli. Perhaps, 8-MOP addition to DNA cannot be inhibited by antioxidants due to steric hindrance. The role of 8-MOP photoaddition to DNA in the induction of PUVA-erythema is discussed.