Methionine aminopeptidase (MetAP) enzymes require a divalent metal ion such as Mn(II), Fe(II), Co(II), Ni(II), or Zn(II) for its removal of the N-terminal methionine from newly synthesized proteins, but it is not certain which of these ions is most important in vivo. Metalloform-selective MetAP inhibitors could be valuable for defining which metals are physiologically relevant for MetAP activation and could serve as leads for development of new therapeutic agents. We have screened a library of 43 736 small drug-like molecules against Escherichia coli MetAP and identified two groups of potent and highly metalloform-selective inhibitors of the Co(II)-form, and of the Mn(II)-form, of this enzyme. Compound 1 is 790-fold more selective for the Co(II)-form, while compound 4 is over 640-fold more potent toward the Mn(II)-form. The X-ray structure of a di-Mn(II) form of E. coli MetAP complexed with the Mn(II)-form-selective compound 4 was obtained, and it shows that the inhibitor interacts with both Mn(II) ions through the two oxygen atoms of its free carboxylate group. The preferential coordination of the hard (oxygen) donors to Mn(II) may contribute to its superb selectivity toward the Mn(II)-form.

The limited availability of ammonia (NH) measurements is currently a barrier to understanding the vital role of NH in secondary aerosol formation during haze pollution events and prevents a full assessment of the atmospheric deposition of reactive nitrogen. The observational gaps motivated us to design this study to investigate the spatial distributions and seasonal variations in atmospheric NH on a national scale in China. On the basis of a 1-year observational campaign at 53 sites with uniform protocols, we confirm that abundant concentrations of NH [1 to 23.9 μg m] were identified in typical agricultural regions, especially over the North China Plain (NCP). The spatial pattern of the NH surface concentration was generally similar to those of the satellite column concentrations as well as a bottom-up agriculture NH emission inventory. However, the observed NH concentrations at urban and desert sites were comparable with those from agricultural sites and 2-3 times those of mountainous/forest/grassland/waterbody sites. We also found that NH deposition fluxes at urban sites account for only half of the emissions in the NCP, suggesting the transport of urban NH emissions to downwind areas. This finding provides policy makers with insights into the potential mitigation of nonagricultural NH sources in developed regions.

For potential application of zeolite in environmental protection, the instantaneous adsorption of volatile nitrosamines in gas stream by zeolites was studied by a gas chromatography technique. Three volatile nitrosamines, N-nitrosodimethylamine, N-nitrosopyrrolidine, and N-nitrosohexamethyleneimine, were chosen as adsorbates. The influence of adsorption temperature, flow rate of gas stream, and the mixed nitrosamines on the adsorption of zeolites was examined. Furthermore, the adsorption isotherms of nitrosamines were fitted with the Freundlich equation for the first time. Zeolite NaY showed the highest capacity to capture the nitrosamines in the gas stream containing sidestream smoke from cigarettes at ambient temperature, providing an efficient candidate for protection of environment and public health.