Fractionation and amino acid composition of an aspartic acid-containing thermal proteinoid population

The heterogeneity of an aspartic acid-containing thermal polymer population has been studied by anion exchange chromatography, amino acid analysis of the resulting fractions and data processing by the principal components method. By using stepwise or continuous gradients of ionic strength both saw-toothed or bell-shaped elution profiles were obtained. This behaviour and the amino acid composition of analyzed fractions suggest a relatively high degree of heterogeneity in the polymer population although less than theoretically expected. This conclusion is compared with the findings reported in proteinoids made by similar procedures.     

The effectiveness of the O(6)-alkylguanine-DNA alkyltransferase encoded by the ogt(ST) gene from S. typhimurium in protection against alkylating drugs, resistance to O(6)-benzylguanine and sensitisation to dibromoalkane genotoxicity

Here we demonstrate that the Ogt(ST) from Salmonella typhimurium is a highly efficient O(6)-alkylguanine-DNA alkyltransferase (AGT) in affording protection against antitumour chloroethylating drugs (1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU)). In addition, Ogt(ST) is refractory to O(6)-benzylguanine (BG) inactivation and its expression provides only minor sensitisation to genotoxicity by environmental dibromoalkanes (DBE). No other of the assayed bacterial or human AGTs displayed such advantageous properties for chemoprotective gene therapy strategy. Our observations indicate that the Ogt(ST) AGT might be, under some circumstances, of potential use to improve cancer chemotherapy. At least, its properties may provide further insight into the design of human AGT variants that could be expressed in normal or tumour cells to provide either protection or ablation.     

Inhibition of aconitase and fumarase by nitrogen compounds in Rhodobacter capsulatus

High levels of aconitase and fumarase activities were found in Rhodobacter capsulatus E1F1 cells cultured with nitrate as the sole nitrogen source either under light-anaerobic or dark-aerobic conditions. Both activities were strongly and reversibly inhibited in vitro by nitrite or nitric oxide, whereas nitrate or hydroxylamine showed a lower effect. Other enzymes of the tricarboxylic acids cycle such as malate dehydrogenase or isocitrate dehydrogenase were not affected by these nitrogen compounds. When growing on nitrate in the dark R. capsulatus E1F1 cells accumulated nitrite intracellularly, so that an in vivo inhibition of aconitase and fumarase could account for the strong inhibition of growth observed in the presence of nitrite under dark-aerobic conditions.Abbreviations ACO aconitase - FUM fumarase - MDH malate dehydrogenase - ICDH isocitrate dehydrogenase - TCA tricarboxylic acid