Fig. 3.

(A) Stereo diagram of a single molecule of the trans-(10R)-BaP DE dG adduct showing its absolute configuration. (B) A view of the crystalline adduct, looking down a line between C10a of the pyrene and C2g of the guanine chromophore, that depicts the negative screw sense of their transition moments near 250 nm. For both guanine (20, 21) and pyrene (22) these transition moments are parallel to their long axes. The relevant portion of the CD spectrum in methanol of a derivative lacking the O⁶-allyl group and with tert-butyldimethylsilyl protecting groups on the deoxyribose (15) shows a negative first Cotton effect and a positive second Cotton effect (heavy line), as predicted from the negative chirality observed in the crystal.