Interaction of mutagenic tryptophan pyrolysate with DNA

Abstract
The interactions of DNA duplexes with 3‐amino 1,4‐dimethyl‐5H‐pyrido[4,3‐b]indole(Trp‐P‐1), a potent mutacarcinogen isolated from tryptophan pyrolysate, have been studied using CD spectroscopy. The results are that (a) the spectral change of B‐form DNA caused by the interaction with Trp‐P‐1 is biphasic, i.e. the enlargement of CD bands characteristic to the B‐DNA conformation in the range of r ([Trp‐P‐1]/[DNA]) = 0–2.5, followed by the rapid transition to the non‐B conformation at r > 2.5; (b) this transition degree of B to non‐B conformation of DNA is not necessarily dependent on the G‐C content; and (c) the salt‐induced Z‐DNA is transformed to B‐DNA (0 < r < 0.1) and then to non‐B‐DNA (r > 5), depending on the concentration of Trp‐P‐1 added. These data indicate that the non‐covalent interaction of Trp‐P‐1 with DNA is mainly dependent on the B‐DNA conformation.

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