Promotion by SF6 of a Radiolytically Induced Chain Reaction for the Geometrical Isomerization of cis or trans-Butene-2 in Dilute Gaseous Mixtures
FOR several years SF6 has been used in radiolytic studies because of its high cross-section for capture of low-energy electrons and consequent effect on observable products resulting from positive-ion neutralization reactions. A reduced yield of H2 from irradiated propane has been reported1 and attributed to electron scavenging by the small proportions of SF6 present. On the other hand, SF6 does not affect the H2 yield from irradiated liquid unsaturates such as trans-butene-2 (ref. 2), indicating that ionic species may not be important with respect to H2 formation from these olefines.
Hydrogen Formation in the Radiolyses of Liquid Butene−1 and trans‐Butene−2
The effect of temperature and various electron or positive‐ion scavengers on hydrogen formation in the radiolyses of liquid butene−1 and trans‐butene−2 have been examined. The hydrogen formation is not appreciably affected by temperature and these additives, which indicates that thermal free radicals and ionic species may not play an important role in hydrogen formation from these olefins. The liquid‐phase radiolyses of C4H8−1—C4D8−1 and trans‐C4H8−2‐trans‐C4D8−2 mixtures have also been investigated. The data indicate that hydrogen for the most part may be formed by bimolecular processes. The results have led to the conclusion that the mechanism of the hydrogen formation may be interpreted in terms of the hydrogen‐atom abstraction reaction of hot hydrogen atoms or the equivalent formed by the direct excitation which may involve ``superexcitation.''
Target of inhibition by the anti-lipogenic antibiotic cerulenin of sterol synthesis in yeast.
Abstract The antibiotic cerulenin inhibited the incorporation of 14 C-acetyl-CoA by 67% at a concentration of 9 × 10 −6 M but not that of 14 C-HMG-CoA into the non-saponifiable fraction in a cell-free extract of Saccharomyces cerevisiae . Cerulenin markedly inhibited the activity of partially purified HMG-CoA synthase. No inhibition of acetoacetyl-CoA thiolase activity was observed in the same preparation of HMG-CoA synthase. Therefore, cerulenin inhibition of overall sterol synthesis may be accounted for by the specific inhibition of HMG-CoA synthase activity.