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Biomedical subjects

A M Kapuler

Publications and source records attributed to A M Kapuler.

13 recordsLinked to original sources
PubMed1971

Energy transfer in modified DNA.

Energy transfer at room temperature and in aqueous solution between two hydrocarbon chromophores, 2-acetylaminofluorene and 7-methylbenz(a)anthracene, covalently attached to DNA and to homopolynucleotide models is described. Transfer, as evidenced by changes in fluorescence intensity and polarization, is a function of secondary structure.

Acetates↗
PubMed1970

Q-beta-replicase and E. coli transcriptase: requirements for substrate selection as revealed by a study of base analogs.

Base selection by the Qbeta-replicase and E. coli transcriptase has been studied using substrate analogs. Six analogs with normal hydrogen-bonding sites were polymerized by both enzymes. Three analogs containing ring substitutions which affect the conformation at the glycosyl bond would not substitute for their normal congeners. The remaining analog was an excellent substrate for the transcriptase but not the replicase.The results imply that the base selection procedure has stringent requirements for substrate conformation. Part of the restriction may derive from the requirement that template and substrates conform to the stereochemical constraints of a double helix. In the Qbeta-replicase reaction, synthesis in the presence of substrate analogs displayed abortive kinetics, implying that the replicase reaction can be uniquely curtailed by substrate analogs.

Binding Sites↗
PubMed1970

Properties of RNA transcriptase in reovirus subviral particles.

Subviral particles containing reovirus RNA transcriptase have been isolated from extracts of virus-infected mouse fibroblast cells. The purified particles which lacked the outer protein capsomeres of the mature virion had a buoyant density of 1.43-1.44 g/ml in CsCl and contained all of the double-stranded RNA genome of the intact virus. The particles were free of nuclease activity. RNA synthesis required all four ribonucleoside triphosphates and was dependent on magnesium or manganese; optimal activity required potassium or ammonium ions. In the presence of a ribonucleoside triphosphate regenerating system, reaction rates were linear for 20 hr. RNA yields of 40-fold in excess of input template could be obtained. Completed RNA chains were released from the subviral particles. In the course of RNA synthesis, the double-stranded RNA template was fully conserved. The RNA products formed in vitro displayed profiles in sucrose gradients similar to those found for in vitro reovirus mRNA. The RNA products were single-stranded and did not self-anneal. Over 90 percent of the transcriptase products could be annealed with template double-stranded RNA. The annealed products migrated in acrylamide gels as double-stranded RNA, indicating efficient in vitro transcription.

Centrifugation, Density Gradient↗