Three enzymes in Escherichia coli which break down ribonucleic acid are now known. One is polynucleotide phosphorylase (I), which in the presence of phosphate yields ribonucleoside 5’-diphosphates. A ribonuclease, which will be called ribonuclease I, is bound to 30 S ribosomes in latent form. When released from the ribosomes it attacks RNA to yield ribonucleoside 3’-phosphates via a 2’) 3’-cycl...

bone like hydroxyapatite (nhap) was synthesized via an in situ biomimetic process in presence of wheat starch. the effect of polymer concentration alteration on the final structure of nhap was investigated. formation of the nhap at room temperature was confirmed by x-ray diffraction (xrd) and fourier transform infrared spectroscopy (ft-ir). size and morphology of the nhap samples were character...

DNA molecules cut with endonuclease R Eco Ri can be joined at Eco Ri cleavage sites by incubation with polynucleotide ligase. In order to define the optimum conditions for this reaction, linear Simian Virus 40 DNA molecules (SV40(Lri)) produced by endonuclease R Eco Ri cleavage of SV40 form i DNA were joined using polynucleotide ligases specified by bacteriophage T4 and Escherichia coli. We hav...

We describe a method leading to the formation of closed circles of rDNA starting from total DNA of Xenopus laevis. Linear DNA molecules were digested with exonuclease 3 and self-annealed. Open circles were enriched and covalently closed by the simultaneous use of polynucleotide kinase, DNA polymerase and polynucleotide ligase. Closed circles of rDNA1 were shown to be alkali-resistant, to have h...

Oligoribonuclease, an exoribonuclease specific for small oligoribonucleotides, was initially characterized 20 years ago (S. K. Niyogi and A. K. Datta, J. Biol. Chem. 250:7307-7312, 1975) and shown to be different from RNase II and polynucleotide phosphorylase. Here we demonstrate, using mutant strains and purified enzymes, that oligoribonuclease is not a manifestation of RNases D, BN, T, PH, an...