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Biomedical subjects

H Sternbach

Publications and source records attributed to H Sternbach.

At least 73 records · Page 4Linked to original sources
PubMed1976

Stereochemistry of polymerization by DNA-dependent RNA-polymerase from Escherichia coli: an investigation with a diastereomeric ATP-analogue.

The phosphodiester bond formation by DNA-dependent RNA-polymerase (RNA nucleotidyltransferase, nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) can in principle result in retention, inversion, or racemization of configuration at the alpha-phosphorus of the nucleoside 5'-triphosphate being polymerized. As a first step in elucidating the stereochemistry of this reaction, one diastereomer (A) of adenosine 5'-O-(1-thiotriphosphate) (ATPalphaS) was polymerized with UTP in the presence of poly(dA-dT)-poly(dA-dT). The resulting polymer was enzymatically cleaved to uridine 2',3'-cyclic phosphorothioate which was determined to be the endo-isomer by comparison with an authentic sample. This shows that no reacemization had occurred and that isomer A of ATPalphaS gives a phosphorothioate diester bond with the R-configuration. Whether this represents inversion of retention of configuration awaits elucidation of the absolute configuration of isomer A for ATPalphaS.

Adenosine Triphosphate↗
PubMed1975

Rapid isolation of highly active RNA polymerase from Escherichia coli and its subunits by matrix-bound heparin.

1. RNA polymerase from Escherichia coli is selectively and strongly retained by a heparin-substituted agarose and can be eluted therefrom by a neutral buffer containing 0.6 M salt. The method is applicable to relatively crude preparations of the enzyme on a preparative scale giving highly purified RNA polymerase in excellent yield. The enzyme obtained by this procedure shows the highest specific activity so far reported and is pure and enriched in factor sigma as indicated by dodecylsulfate gel electrophoresis. 2. Based on the differential affinity of the subunits of the enzyme for the heparin-carrying gel matrix, a method for separation of alpha, beta' + beta and sigma subunits by application of urea and salt-containing buffers is described. Upon recombination and dialysis with urea-free buffer 40-50% of the enzyme activity is restored.

Chromatography, Affinity↗
PubMed1975

[Reactivity of the 3'-terminal oligonucleotide Sequence C-A-C-C-A of tRNAPhe and tRNAVal from baker's yeast upon N-oxidation with monoperphthalic acid as compared to the oligonucleotides C-A-C-C-A and A-A-A-U-C-A-C-C-A (author's transl)].

The nucleobases adenine and cytosine were subjected to N-oxidation by monoperphthalic acid at pH 7 and 0 degrees C in tRNAPhe, in the 3'-terminal pentanucleotide C-A-C-C-A from tRNAPhe, as well as in tRNAVal and in the 3'-terminal nonanucleotide A-A-A-U-C-A-C-C-A from tRNAVal. In the tRNAs, the oxidative attack occurs stepwise from the 3'-end. First the 3'-terminal adenine is oxidized, then the following two cytosines, then the following adenine. The oligonucleotides are far more reactive than the identical sequences in tRNA and are not oxidized according to a sequential mechanism.

Base Sequence↗