... (+)-benzo(a)pyrene- OH 7 , 8- diol-9,10-epoxide- 2- N-2 guanine adduct HO O H CH3 N N N N H2N Methyl group on N7 Bond to DNA Alkylated guanine Figure 8. 3 Formation of the bulky guanine adduct of (+)-benzo(a)pyrene-7 , 8- diol-9,10-epoxide-2 ... LLC L1618Ch08Frame Page 172 Tuesday, August 13, 2002 5:49 PM O H O + H2N OH N N N N Bond to DNA Guanine bound with DNA HO (+)-benzo(a)pyrene7 , 8- diol-9,10-epoxide-2 O H N N H N N N OH (+)-benzo(a)pyrene- ... activity This is accomplished with the chromogenic substrate 5-bromo-4-chloro-3-indoyl-β-D-galactopyranoside, which is metabolized by β-galactosidase to form a blue product Therefore, when colonies...