The covalent binding of benzo[a]pyrene 4,5-oxide and benzo[a]pyrene-7,8-dihydrodiol 9,10-oxide isomer I and isomer II to nucleic acids in aqueous acetone solution has been investigated. Benzo[a]pyrene 4,5-oxide reacted preferentially with guanosine residues. On the other hand, benzo[a]pyrene-7,8-dihydrodiol 9,10-oxide isomer I and II reacted extensively with guanosine, adenosine, and cytidine residues. Time course studies showed that the reactivity of isomer I or isomer II with homopolyribonucleotides followed the order poly(G) greater than poly(A) greater than poly(C). Alkaline or enzymatic hydrolysis of the modified nucleic acids and subsequent chromatography on Sephadex LH-20 columns yielded benzo[a]pyrene-nucleotide adducts. These were enzymatically converted to the corresponding nucleosides which were resolved into several distinct components by high-pressure liquid chromatography. Evidence was obtained for the presence of multiple nucleoside adducts of guanosine, adenosine, cytidine, deoxyguanosine, deoxyadenosine, and deoxycytidine. The HPLC profiles of adducts formed with isomer I were different from the corresponding profiles of adducts formed with isomer II. Structural aspects of these nucleoside adducts are discussed.

A. 1,lO-Phenanthroline Complexes [ (phen),Mn'" ,0/Mn'"(phen)z]4+ /o\ 1 Mn'"(phen)2]*+ (2) e-3 . p 3 . X B. 2,2'-Bipyridyl Complexes 0 0 CibPYXMn\ '" \Mn".(bpy)J'+ , 1 k ( = o.OZs-' Y n 2 . e-& r(bPYhMn\ 'I' , 'Mn"'(bpy),]2+ ( 4 ) 0 Ep,c = +0.36 V 1 fast Z pared to 2.53 PB (uncorrected) for the solid by the Guoy method a t room temperaturet2 and for 3, Feff = 2.26 f 0.08 p c~g .~~,~~ The reduced magnetic moments that are observed relative to those for the spin-only condition support the conclusion that the di-v-oxo bridged species are stable in solution.Of the two complexes, the mixed-oxidation state bipyridyl complex (2) is slightly easier to oxidize and more difficult to reduce than the corresponding 1,lO-phenanthroline derivative. Also, the coupled chemical reactions occur a t a faster rate for the bipyridyl complexes. This change in chemical and electrochemical reactivity can be accounted for on the basis of the "floppy" bipyridyl ligand compared to the rigid structure of 1 ,lo-phenanthroline.

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