The reaction of chlorodimethylvinylsilane with tertbutyllithium was investigated in the presence of several conjugated dienes. In all cases except with 2,5-dimethylfuran, [2+4] cycloadducts of a silene intermediate are obtained in hydrocarbon solvents. The presence of THF in the reaction mixture suppresses the formation of cycloadducts in favor of 1,3-disilacyclobutanes. In the reaction of dimethylethoxyvinylsilane or dimethylmethoxyvinylsilane with tert-butyllithium the main product is the 1,1-dimethyl2-neopentyl-4-(dimethylalkoxysilyl)silacyclobutane. It is concluded that lithium chloride elimination to give silene intermediates occurs in hydrocarbon solvents. In the presence of strong Lewis bases or when the leaving group on silicon is an alkoxy group, the addition reaction giving a-lithiosilanes occurs and products arising from their coupling reactions are obtained.

Cyclopropanation of the unsaturated fatty acid moieties of membrane phospholipids is a commonly observed phenomenon in a number of bacterial systems. The cyclopropane fatty acids are usually synthesized during and after the transition from exponential growth to stationary phase, or under such environmental conditions as acidic culture pH, low oxygen tension or high salt concentrations. S-Adenosylmethionine, the ubiquitous methyl group donor, provides the methylene bridge carbon in the reaction catalyzed by cyclopropane fatty acid synthase. Also formed in the reaction is S-adenosylhomocysteine, a potent inhibitor of cyclopropane fatty acid synthase, which is degraded by S-adenosylhomocysteine nucleosidase. This work provides evidence for at least two modes of regulation of lactobacillic acid synthesis, the cyclopropane fatty acid formed from cis-vaccenic acid (cis-11,12-octadecenoic acid), in Lactobacillus piantarum.

This work presents the development of a new highly sensitive and selective chemical assay for poly(ADP-ribose) which is routinely useful for the determination of polymer levels in vivo. This method was used to carefully measure poly(ADP-ribose) levels in normal and in DNA-damaged cells. The results of these studies strongly suggest that synthesis of poly(ADP-ribose) is involved in some aspect of DNA repair. A review of the literature is presented in the introduction of this work. Poly(ADP-ribose) synthesis has been implicated in aspects of transcription, in DNA syn thesis, and in DNA repair largely based on evidence from in vitro studies. It is apparent that current methodology has not allowed the routine quantification of poly(ADP-ribose) in vivo, hence the lack of i^n vivo data concerning the function(s) of the polymer. The body of this work presents the development of two chemical methods for the quantification of poly(ADP-ribose) and the application of one of these methods to the measurement of polymer levels in normal and DNA-damaged cells. Preliminary studies are presented on the utilization of combined gas chromatography/mass spectroscopy for the selective quantification of nucleoside derivatives. A second method makes use of the unique chemistry of the polymer for quantification. The polymer …

The enzyme 3-Hydroxy-3- Methylglutaryl Coenzyme A Reductase catalyzes the rate limiting step of hepatic cholesterol biosynthesis and is unique among the enzymes in the early part of the pathway in that it is membrane bound. This gives rise to potential regulation of the enzyme through interactions with the endoplasmic reticulum membrane. A purification procedure has been developed which consistently produces enzyme of high specific activity. In order to fully characterize the interactions between HMG-CoA reductase and the lipids in its immediate environment, HMG-CoA reductase was purified to homogeneity and shown to be a protein-lipid complex.

Article on HTP kinetics studies of the reaction of O(2(3)Pj) atoms with H2 and D2 over wide temperature ranges.