Formation and stability of 4-(hydroxymethylnitrosamino)-1-(3-pyridyl)-1-butanone glucuronide, a stable form of reactive intermediate produced from 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, in mice.

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a tobacco-specific nitrosamine, induced lung tumors in rodents and is likely involved in human lung cancer. 4-(Hydroxymethylnitrosamino)-1-(3-pyridyl)-1-butanone (HO-methyl NNK) glucuronide, a glucuronide of the reactive intermediate of NNK, has been identified in rats. The aim of this study is to estimate the role of HO-methyl NNK glucuronide in the tumorigenic effects of NNK. We investigated the urinary excretion and tissue distribution of HO-methyl NNK glucuronide in A/J mice, which are susceptible to NNK carcinogenesis, and C57BL/6J mice, which are resistant to NNK carcinogenesis. The cumulative urinary excretion of the HO-methyl NNK glucuronide in the C57BL/6J mice was more than 20 times higher than in the A/J mouse urine. Tissue concentrations of HO-methyl NNK glucuronide were also higher in the C57BL/6J mice than in the A/J mice. Assessment of the stability of HO-methyl NNK glucuronide in liver homogenates at physiological pH conditions showed that more than 60% of the glucuronide remained until 2 hr of incubation. These results suggested that HO-methyl NNK glucuronide is likely to be a detoxified metabolite and could be one reason for differences in the susceptibility to NNK tumorigenesis between the two strains. Once HO-methyl NNK is formed in tissues, C57BL/6J mice have a high ability to form HO-methyl NNK glucuronide so that HO-methyl NNK, the reactive intermediate formed from NNK, is readily excreted in urine as a stable form.

Organic mediator-induced structural transformation in superlattices of monolayer-protected gold nanoparticles.

N-acetylglutathione (NAG)-protected gold nanoparticles self-assemble into three-dimensional (3D) face-centered cubic (fcc)-type superlattices at an air/water interface under highly acidic conditions. To prepare the well-defined superlattices, 1month's incubation is at least necessary since the size growth of the as-prepared nanoparticles is essential. Addition of 4-pyridinecarboxyic acid (PyC), a bifunctional hydrogen-bonding mediator, promotes the formation of the superlattices, which are created for about 2weeks' storage. Interestingly, PyC-induced nanoparticle superlattices are in a body-centered tetragonal (bct) structure. The fcc-to-bct phase transformation would be due to stronger interaction between NAG and PyC than that between NAG molecules on the gold nanoparticle surfaces.