 Properly speaking, B"a"P is a procarcinogen, meaning that its mechanism of carcinogenesis depends on its enzymatic metabolism to B"a"P diol epoxide.It intercalates in DNA, and the electrophilic epoxide is attacked by nucleophilic guanine bases, forming a bulky guanine adduct.X-ray crystallographic and nuclear magnetic resonance structure studies have shown how this binding distorts the DNA by confusing the double-helical DNA structure.