The photoreactivity of chlorine dioxide

Determining the detailed photoreactivity of radicals that are of importance in atmospheric processes requires information from both laboratory and field measurements and theoretical calculations. Laboratory experiments and quantum calculations have been used to develop a comprehensive understanding of the photoreactivity of chlorine dioxide (OCIO). The photoreactivity is strongly dependent on the medium (gas phase, liquid solution, or cryogenic matrix). These data reveal details of the complex chemistry of OCIO. The potential role of this radical in stratospheric ozone depletion is discussed in accord with these laboratory measurements.     

Chemistry. The motions of an enzyme soloist

Dynamics of proteins are crucial to their function. In his Perspective, Orrit stresses the advantages of studying these dynamics with single-molecule methods--which require no synchronization--rather than with conventional ensemble measurements. He highlights the report by Yang et al., who follow the fluorescence of a single enzyme molecule. Electron transfer from the fluorophore to a quencher induces fluctuations of the fluorescence lifetime along with the fluorophore-quencher distance. The wide range of characteristic times of those fluctuations reveals the complexity of the protein's potential energy landscape. As a new molecular ruler, electron transfer complements other single-molecule methods such as energy transfer (FRET) for distances shorter than a few nanometers.     

The drug dilemma: manipulating the demand

Drug abuse in the United States has posed a dilemma during most of this century. Intemperate use of reinforcing drugs is hazardous to health and safety, but strict prohibition fosters an illicit market with criminal effects that may be equally harmful. The crux of the problem is the willingness of millions of people to risk toxicity and arrest to gain psychopharmacological rewards. Cocaine is the present source of most concern. Recommendations for reducing demand and abuse are given, including the implementation of preventive techniques, the investigation of various treatments, the use of modern chemical and electronic technology, and the development of new pharmacological alternatives.     

The chlorine isotope composition of Earth's mantle

Chlorine stable isotope compositions (delta37Cl) of 22 mid-ocean ridge basalts (MORBs) correlate with Cl content. The high-delta37Cl, Cl-rich basalts are highly contaminated by Cl-rich materials (seawater, brines, or altered rocks). The low-delta37Cl, Cl-poor basalts approach the composition of uncontaminated, mantle-derived magmas. Thus, most or all oceanic lavas are contaminated to some extent during their emplacement. MORB-source mantle has delta37Cl 相似文献