• R K Singh

      Articles written in Journal of Biosciences

    • Uterine RNA synthesis during protein deficiency and steroidmaintained pregnancy in rats

      R K Singh S K Roy

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      Some aspects of uterine RNA synthesis including [3H]-uridine incorpo ration into RNA, activities of RNA polymerases and ribonucleases were studied. It was observed that both normal and pregnant animals, kept on protein-free diet for 15 and 20 days, showed a significant increase inin vivo uptake of [3H]-uridine into total RNA. Activities of RNA polymerase I and polymerase III increased two-fold in animals kept on a protein-free diet; however, RNA polymerase II activity was unaffected by protein restriction. In animals kept on protein-free diet where pregnancy was maintained by exogenous estrogen and progesterone, specific activity of nuclear RNA was further increased and the activities of RNA polymerases I, II and III markedly increased. Levels of RNase were also increased significantly during protein deficiency, thus showing a rapid turn-over of uterine RNA. These observations indicate that during protein restriction, uterine RNA synthesis is regulated at transcriptional level by a selective stimulation of RNA polymerase and RNase also plays an important role.

    • Diverse effects of formate on the assimilatory metabolism of nitrate and nitrite inRhizobium

      R K Singh R M Singh

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      Two strains ofRhizobium, cowpeaRhizobium 32H1 andRhizobium japonicum CB 1809, showed a marked stimulation in growth on addition of formate to the minimal medium containing nitrate as the sole source of nitrogen. The amount of accumulated nitrite and specific nitrate reductase activity was much higher in cultures supplemented with formate than in the control medium. In contrast, growth, consumption of nitrite and specific nitrite reductase activity in minimal medium + nitrite was greatly reduced by the addition of formate. A chlorate resistant mutant (Chl-16) was isolated spontaneously which contained a nitrite reductase which was not inhibited by formate. The results suggest that formate serves as an electron donor for nitrate reductase and inhibits nitrite assimilation inRhizobium

    • (α-Pyridyl) methyl phosphoro-bis-triazolide as a new phosphorylating reagent for internucleotide bond formation

      K Misra M Chaddha A Dikshit R K Singh

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      (α-Pyridyl)methyl phosphoro-bis-triazolide has been found to be a reagent of choice for phosphate protection in oligodeoxyribonucleotide synthesis. The reagent has been used successfully to phosphorylate all the four 5’-and N-protected deoxynucleosides. The resulting 3′-phosphorylated derivatives were found to be fairly stable as either triethyl ammonium salts or cyanoethyl derivatives. The phosphorylated derivatives were used in the preparation of the dimers TpT and d(ApT) in solution phase and a tetramer, TTTT, and a hexamer, d(ATATAT), on solid phase using glass support. The method gave excellent yields. Considerably reduced condensation time (6–9 min) and practically no cleavage of the internucleotide bond during the removal of the group are the advantages.

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