Novel Synthesis of Trisubstituted Olefins for the Preparation of the C16-C30 Fragment of Dolabelide C.

A silicon-tether ring-closing metathesis strategy is reported for the synthesis of trisubstituted olefins flanked by allylic or homoallylic alcohols, which are difficult to obtain by classical ring-closing or cross-metathesis reactions. In addition, a novel Peterson olefination reaction has been developed for the preparation of the allyldimethylsilane precursors, which are versatile synthetic intermediates. This method was then applied to the synthesis of the C16-C30 fragment of dolabelide C.

DNA nicking by ultraviolet radiation is enhanced in the presence of iron and of oxygen.

Double-stranded covalently closed circular supercoiled DNA (ccc DNA) from plasmid pUK 9 was irradiated in vitro at defined wavelengths in the UV region (290, 313 and 365 nm). The nicking was monitored by electrophoresis on agarose gels, ethidium staining and densitometric quantitation of supercoiled and relaxed moieties. At the explored wavelengths, the dose required for introducing one nick per million phosphodiester bonds diminishes with increased concentration of added ferric iron, whereas the effect of cupric iron is practically negligible.

Chemical and biochemical postlabeling methods for singling out specific oxidative DNA lesions.

A survey of the main available chemical and biochemical postlabeling assays for measuring oxidative DNA damage is reported. Two main approaches, radio and fluorescent postlabeling, have been used in order to reach a high level of sensitivity of detection. This is required for the measurement of DNA damage within cells and tissues upon exposure to agents of oxidative stress.