INTERACTION OF NUCLEIC ACIDS .V. CHEMICAL LINKAGE OF 3,4-BENZPYRENE TO DEOXYRIBONUCLEIC ACID IN AQUEOUS SOLUTION

Chemical reactions between the carcinogen, 3,4- benzpyrene, and deoxyribonucleic acid have been carried out in neutral, aqueous solution and at room temperature. Data presented are consistent with the formation of a covalent linkage between 3,4-benzpyrene and deoxyribonucleic acid in these mild conditions. This chemical linkage has been induced by reacting the physical complex with iodine, hydrogen peroxide in the presence and absence of ferrous ion, and with the ascorbic acid model hydroxylating system. Up to 40% of the physically bound 3,4-benzpyrene can be linked covalently to the deoxyribonucleic acid under appropriate conditions. In these same reactions, a noncarcinogenic isomer, 1,2-benzpyrene, is linked to deoxyribonucleic acid only to a very limited extent. The covalently linked benzpyrene cannot be extracted by organic solvents which remove over 99% of the physically bound benzpyrene from deoxyribonucleic acid. The chemical linkage was further characterized by sucrose gradient electrophoresis and gel filtration of the chemical complex before and after enzymic hydrolysis. The present data suggest that benzpyrene free radicals (possibly cationic) may be involved as intermediates in the reactions. © 1969, American Chemical Society. All rights reserved.