Nitrofuran enhancement of microsomal electron transport, superoxide anion production and lipid peroxidation

Addition of nifurtimox (a nitrofuran derivative used for the treatment of Chagas' disease) to rat liver microsomes produced an increase of (a) electron flow from NADPH to molecular oxygen, (b) generation of both superoxide anion radical (O₂^?) and hydrogen peroxide, and (c) lipid peroxidation. The nifurtimox-stimulated NADPH oxidation was greatly inhibited by NADP⁺ and p-chloromercuribenzoate, and to a lesser extent by SKF-525-A and metyrapone. These inhibitions reveal the function of both the NADPH-cytochrome P-450 (c) reductase and cytochrome P-450 in nifurtimox reduction. Superoxide dismutase, catalase (in the presence of superoxide dismutase), and hydroxyl radical scavengers (mannitol, 5,5-dimethyl-1-pyrroline-1-oxide) inhibited the nifurtimox-stimulated NADPH oxidation, in accordance with the additional operation of a reaction chain including the hydroxyl radical. Further evidence supporting the role of superoxide anion and hydroxyl radicals in the nifurtimox-induced NADPH oxidation resulted from the effect of specific inhibitors on NADPH oxidation by O₂^? (generated by the xanthine oxidase reaction) and by OH. (generated by an iron chelate or the Fenton reaction). Production of O₂^? by rat kidney, testes and brain microsomes was significantly stimulated by nifurtimox in the presence of NADPH. It is postulated that enhanced formation of free radicals is the basis for nifurtimox toxicity in mammals, in good agreement with the postulated mechanism of the trypanocide effect of nifurtimox on Trypanosoma cruzi.     

Gene ompR and regulation of microcin 17 and colicin e2 syntheses.

The production of microcin 17 is controlled by plasmid pRYC17. Chromosomal mutants unable to produce a normal amount of microcin were isolated in Escherichia coli. One of the mutations maps in the ompR locus, indicating that an active OmpR product is required for the synthesis of microcin 17. The same conclusion was obtained for the synthesis of colicin E2. Therefore, two new functions of the regulatory gene ompR have been revealed.     

Cellulolytic enzymes for the hydrolysis of leached beet cosette

Summary Cellulolytic fungi were isolated from rotting leaves and tested for extra-cellular cellulase activities (CMCase, avicelase, cellobiase and xylanase). The effect of the proportion of the enzyme activities on the rate of degradation of leached beet cosette was observed using a range of supernatant fluids in appropriate combinations. At low cosette concentrations (1.5–3.0 g/l), avicelase and cellobiase were the rate limiting enzymes; avicelase in the initial stages of reaction and cellobiase after 6–8 hours, when cellobiose inhibition becomes important. A ratio of celiobiase to avicelase of approx 2.0 was established as appropriate. At higher substrate concentrations (10 g/l, 40 g/l) the best cellobiase to avicelase ratio was maintained and up to 40% hydrolysis was obtained in the 10 g/l incubation with 10 Uav/l and 20 Ucellob/l. At 100 g/l cosette concentration, substrate inhibition was observed.     

Operation of the glucose-fatty acid cycle after glycogenolysis induced by treatment with nicotinic acid.

The intramembranous segment of glycophorin A has been localized to a 35-amino acid peptide. This has been isolated by a new procedure in which acid-insoluble peptides of a tryptic digest of detergent-purified glycophorin A are fractionated by countercurrent distribution. Amino acid sequence analyses, using both manual and automatic Edman degradation techniques, indicate that this peptide has a unique sequence in contrast to earlier work (J. P. Segrest, I. Kahane, R. L. Jackson, and V. T. Marchesi, 1973, Biochem. Biophys. Res. Commun., 49, 964–969). Ambiguities at three positions have been resolved, and sequencing errors at two additional positions have been corrected. One segment of this peptide has an uninterrupted stretch of 22 uncharged amino acids, and it is likely that this is the part which spans the lipid bilayer of the membrane. The complete 35-residue peptide has an apparent molecular weight in the 6000–8000 range, when analyzed on sodium dodecyl sulfate gels, suggesting that it forms dimers under these conditions. This result is consistent with our earlier proposal that intact glycophorin A molecules exist as dimers in sodium dodecyl sulfate which are stabilized by noncovalent associations between hydrophobic segments of their polypeptide chains.     

Preparation of an enantiomerically pure, highly porous metalloorganic crystal

We report the synthesis and the structure determination of tris-(4,5-diazo-spiro-bifluorene)ruthenium(II) chloride, a chiral building block whose racemic mixture solution spontaneously resolves and forms two crystalline, enantiomerically pure, porous networks composed exclusively of the Λ or Δ atropisomers. The extended chiral channels are occupied by water molecules (approximately 20% by weight) and the chloride counter-ions.     

Separation by high-performance liquid chromatography of penicillins with C4 to C10 aliphatic side chains

A suitable and rapid method for the simultaneous determination of different aliphatic penicillins is described. Butyryl-, pentanoyl-, hexanoyl-, heptanoyl-, octanoyl-, nonanoyl- and decanoylpenicillin can be completely separated by high-performance liquid chromatography using an isocratic elution mode (50 mM H2KPO4, pH 5.0:methanol, 45:55 v/v). Under these conditions, retention times for C4 to C10 aliphatic side-chain penicillins were 2.5, 2.8, 4.1, 5.8, 8.9, 15.3, and 28.2 min. The benzylpenicillin retention time was 3.3 min.