There is a growing interest in the photoregulation of biological functions, due to the high level of spatiotemporal precision achievable with light. Additionally, light is non-invasive and waste-free. In particular, the photoregulation of oligonucleotide structure and function is a rapidly developing study field with relevance to biological, physical and material sciences. Molecular photoswitches have been incorporated in oligonucleotides for 20 years, and the field has currently grown beyond fundamental studies on photochemistry of the switches and DNA duplex stability, and is moving towards applications in chemical biology, nanotechnology and material science. Moreover, the currently emerging field of photopharmacology indicates the relevance of photocontrol in future medicine. In recent years, a large number of publications has appeared on photoregulation of DNA and RNA structure and function. New strategies are evaluated and novel, exciting applications are shown. In this comprehensive review, the key strategies for photoswitch inclusion in oligonucleotides are presented and illustrated with recent examples. Additionally the applications that have emerged in recent years are discussed, including gene regulation, drug delivery and materials design. Finally, we identify the challenges that the field currently faces and look forward to future applications.

Recent developments in reversible photoregulation of oligonucleotide structure and function.

The importance of aryl amines as raw materials for various applications has spurred extensive research in developing economic processes for the reduction of nitroarenes. Developing green methodologies is now a compelling discipline for synthetic organic chemists. The recent surge in nanochemistry has led to the development of some interesting applications in nitro reduction processes. This review discusses some recent examples of reports in this field. The different methods are classified based on the source of hydrogen utilized during reduction and the mechanism involved in the reduction process.

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Advancement in methodologies for reduction of nitroarenes

This literature review encompassing information available through 1980 and limited coverage in 1981, emphasizes results useful in assessing the potential toxic effects of nitrobenzene to man. Nitrobenzene exposure in man or experimental animals is most often associated with methemoglobinemia. Histopathologic changes also are observed in the hemato-lymphoreticular system, central nervous system, and liver. In addition, lesions have been reported in adrenals and testes. No information was found on carcinogenic or teratogenic potential, fertility, or reproductive effects of nitrobenzene. Results from Ames Salmonella assay are negative but test procedures are questionable; metabolites give positive results. Metabolism of nitrobenzene involves either oxidation or reduction yielding p-aminophenol and p-nitrophenol, and other reduced intermediates. From the foregoing, several aspects of nitrobenzene toxicity have been identified which warrant further study. Recommendations are made for chronic and subchronic exposure of test animals via inhalation to assess various toxicological endpoints. In addition, the relationship of nitrobenzene metabolism to its toxicity needs to be established. Genotoxic effects of nitrobenzene also need study.

A Critical Review of the Literature on Nitrobenzene Toxicity

1. The metabolism of [14C]aniline in the cattle tick, Boophilus microplus (Canestrini) at 40 and 300 mug per animal) and in the spider, Nephila plumipes (at 40 mug per 100 mg) were studied. 2. In both species hydroxylation occurred yielding both free and conjugated o-and p-aminophenols. 3. The water-soluble metabolites affording aniline on acid hydrolysis were examined, and gamma-glutamylanilide (23% of dose) was identified as a tick metabolite (40 mug dose). This metabolite was not found in extracts of dosed spiders.

S. Willox

Papers

Nitrobenzene reduction and reductive cleavage of azobenzenes in two species of arachnida