DNA adduct formation of the aromatic amine, 4-aminobiphenyl (4-ABP), a known human carcinogen present in tobacco smoke, and the heterocyclic aromatic amines (HAAs), 2-amino-9H-pyrido[2,3-b]indole (AαC), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), and 2-amino-3,8-dimethylmidazo[4,5-f]quinoxaline (MeIQx), potential human carcinogens, which are also present in tobacco smoke or formed during the high-temperature cooking of meats, was investigated in freshly cultured human hepatocytes. The carcinogens (10 μM) were incubated with hepatocytes derived from eight different donors for time periods up to 24 h. The DNA adducts were quantified by liquid chromatography-electrospray ionization mass spectrometry with a linear quadrupole ion trap mass spectrometer. The principal DNA adducts formed for all of the carcinogens were N-(deoxyguanosin-8-yl) (dG-C8) adducts. The levels of adducts ranged from 3.4 to 140 adducts per 107 DNA bases. The highest level of adduct formation occurred with AαC, followed by 4-ABP, then by PhIP, MeIQx, and IQ. Human hepatocytes formed dG-C8-HAA-adducts at levels that were up to 100-fold greater than the amounts of adducts produced in rat hepatocytes. In contrast to HAA adducts, the levels of dG-C8-4-ABP adduct formation were similar in human and rat hepatocytes. These DNA binding data demonstrate that the rat, an animal model that is used for carcinogenesis bioassays, significantly underestimates the potential hepatic genotoxicity of HAAs in humans. The high level of DNA adducts formed by AαC, a carcinogen produced in tobacco smoke at levels that are up to 100-fold higher than the amounts of 4-ABP, is noteworthy. The possible causal role of AαC in tobacco-associated cancers warrants investigation.

Alkanethiol-capped gold nanoparticles dispersed in n-dodecane were studied by spectroscopic ellipsometry and were modeled using Mie scattering theory. The refractive index in the visible and near-infrared depended on the volume fraction of gold nanoparticles, in good agreement with the theoretical expectation that such dispersed plasmonic nanoparticles can act as low or tunable refractive index materials at specific optical wavelengths.

Background: 2-Amino-9H-pyrido [2,3-b]indole (A␣C) is a carcinogen formed in tobacco smoke, but little is known about its metabolism in humans. Results: UDP-Glucuronosyltransferases catalyze the binding of N-oxidized-A␣C to DNA. Conclusion: Glucuronidation, normally a detoxication pathway, contributes to the genotoxicity of A␣C. Significance: The exposure to and UGT bioactivation of A␣C provides a biochemical mechanism for the elevated risk of liver and digestive tract cancers in smokers.