The reaction of 1,2-dibromoethane and glutathione with DNA in the presence of glutathione S-transferase results in the formation of a single major DNA adduct, which can be released by thermal hydrolysis at neutral pH and separated by octadecylsilyl and propylamino high-performance liquid chromatography. The same DNA adduct is the only major one formed in livers of rats treated with 1,2-dibromo[1,2-14C]ethane. The DNA adduct was identified as S-[2-(N7-guanyl)ethyl]glutathione: (1) The chromatographic behavior was altered by treatment with gamma-glutamyl transpeptidase or Streptomyces griseus protease. (2) The molecular ions observed in positive and negative mode fast atom bombardment mass spectrometry were those expected for the structure when either glycerol or a mixture of dithiothreitol and dithioerythritol was used as the bombardment matrix. (3) The two-dimensional 1H NMR correlated spectroscopy spectrum of the DNA adduct was compared to the spectra of glutathione, oxidized glutathione, and N7-methylguanine and found to be consistent with the assigned structure. No evidence for in vitro or in vivo opening of the guanyl imidazole ring was observed under these conditions. The structure of the adduct supports a pathway involving enzyme-catalyzed conjugation of 1,2-dibromoethane with glutathione, non-enzymatic dehydrohalogenation of the resulting half-mustard to form a cyclic episulfonium ion, and attack of the N7 nitrogen of DNA guanine on the episulfonium ion to generate this major DNA adduct, which may be related to the carcinogenicity of this chemical.

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Zusammenfassung: Die überwinternden Eier des Seidenspinners färben sich in den ersten Tagen purpurschwarz. Die Bildung der dafür verantwortlichen Ommochrome und die Konzentrationen der als Vorstufen für ihre Synthese geltenden Substanzen (Tryptophan, Kynurenin und 3-Hydroxy-kynurenin) wurden in Abhängigkeit von der Zeit ge-Summary: The hibernating eggs of the silkworm turn purple-black by the production of ornmochromes within the first four days after the egglaying. The concentrations of xanthommatine and ommine as well as those of tryptophan, kynurenine and 3-hydroxykynurenine were determined at various stages. The levels of tryptophan (maximum at 3,5 days) and of kynurenine (maximum at 1 day

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