Iron-sulfur proteins: ancient structures, still full of surprises.

This article is a survey of the properties and functions of Fe-S proteins under the following headings: sulfur and iron; iron-sulfur clusters; evolution of cofactor use; early observations; complex and extended clusters; sulfur exchange and core interconversions; synthesis and biosynthesis of Fe-S clusters; functions of Fe-S clusters: electron transfer, electron delocalization, spin states and magnetism, covalency of sulfur bonds; non-electron transfer functions of Fe-S clusters: substrate binding and catalysis, regulatory and sensing functions.

Steroidal allylic fluorination using diethylaminosulfur trifluoride: a convenient method for the synthesis of 3 beta-acetoxy-7 alpha- and 7 beta-fluoroandrost-5-en-17-one.

This paper discusses our findings regarding fluorination of the diastereomeric 3 beta-acetoxy-7-hydroxyandrost-5-en-17-ones (3 and 4) at the allylic 7-hydroxyl group using diethylaminosulfur trifluoride under various experimental conditions. The reaction led to the formation of allylic 7 alpha- and 7 beta-fluoro derivatives, 6 and 7, contaminated with small amounts of 3 beta-acetoxy-5 alpha-fluoroandrost-6-en-17-one (8), the rearrangement product, and 3 beta-acetoxyandrosta-4,6-dien-17-one (9), the elimination product. However, synthesis of 3 beta-acetoxy-7 alpha-fluoroandrost-5-en-17-one (6) and 3 beta-acetoxy-7 beta-fluoroandrost-5-en-17-one (7) has been achieved in high isomeric purity by careful manipulation of the experimental conditions.

Crystals and structures of cytochrome c oxidases--the end of an arduous road.

Crystal structures of cytochrome c oxidases, one of which is the largest membrane-bound protein complex crystallized to date in a form suitable for X-ray diffraction, have recently been solved. The information from these accomplishments confirms many of the structural properties known from earlier spectroscopic and analytical studies, and provides a basis for understanding the complex mechanisms of electron transfer and proton pumping.

Structure-function studies of [2Fe-2S] ferredoxins.

The ability to overexpress [2Fe-2S] ferredoxins in Escherichia coli has opened up exciting research opportunities. High-resolution x-ray structures have been determined for the wild-type ferredoxins produced by the vegatative and heterocyst forms of Anabaena strain 7120 (in their oxidized states), and these have been compared to structural information derived from multidimensional, multinuclear NMR spectroscopy. The electron delocalization in in these proteins in their oxidized and reduced states has been studied by 1H, 2H, 13C, and 15N NMR spectroscopy.