- Formation of O6,7-dimethylguanine residues in calf thymus deoxyribonucleic acid treated with carcinogenic N-methyl-N-nitrosourea in vitro.
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Treatment of calf thymus deoxyribonucleic acid (DNA) in vitro with a methylating carcinogen, N-methyl-N-nitrosourea (MNU), in phosphate buffer (pH 7.2) resulted in formation of O6,7-dimethylguanine residues in DNA besides the well-known methylated DNA adducts, 7-methylguanine, O6-methylguanine and 3-methyladenine. The product ratio (%) of O6,7-dimethylguanine versus 7-methylguanine was 0.32 after one MNU treatment. The significance of formation of O6,7-dimethylguanine residues in DNA is discussed briefly in relation to the carcinogenicity of MNU.
- Kohda,Sawada,Kawazoe
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- Synthesis of heteromine C from guanine
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Heteromine C previously isolated from a Taipei folk medicine plant, has been synthesised for the first time by selective methylation reactions starting from guanine. Thermal rearrangement to 1-methylherbipoline takes place when heteromine C is heated. It is shown that treatment of O6,9- dimethylguanine with methyl iodide gives the O6,7,9-trimethylguaninium iodide with complete selectivity, while similar reaction on O6,7- dimethylguanine results in methylation both in the 3- and 9-position.
- Jakobsen, Erik,Gundersen, Lise-Lotte
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p. 935 - 940
(2007/10/03)
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