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Biomedical subjects

L F Cavalieri

Publications and source records attributed to L F Cavalieri.

33 records · Page 2Linked to original sources
PubMed1974

Extent of double strandedness in avian myeloblastosis virus RNA.

The extent of double strandedness of avian myeloblastosis virus 70S RNA has been determined from fluorescence measurements of the intercalation of ethidium bromide. We have shown that 50% of the nucleotides of 70S RNA in solution are in a stable helical configuration. This value does not include small helical regions that are too unstable to permit intercalation of the dye. The avian myeloblastosis virus RNA as it exists within the virion has the same degree of helicity as the free 70S RNA. Heating the free 70S RNA to 55 or 70 C, followed by cooling, does not measurably change the degree of helicity; the subunits therefore have as much helicity as the parent molecule.

Avian Leukosis Virus↗
PubMed1971

Multiple molecular species of Escherichia coli DNA polymerase.

DNA polymerase activity from Escherichia coli can be demonstrated in various sized molecules ranging in molecular weight from about 10,000 to 120,000 or higher. The characterization of the smaller species is difficult because of their pronounced tendency toward aggregation; the smallest apparently aggregates most readily. The results indicate the following molecular weight classes: 10,000-20,000; 40,000-50,000; 75,000-85,000, and 100,000-120,000. The same classes were obtained with several methods of analysis of material that had been purified in a number of ways, one of which is a new DNA-acrylamide gel chromatographic procedure. The lowest molecular weight species shows no exonucleolytic activity. A proteolytic inhibitor, phenylmethyl sulfonylfluoride, did not eliminate the small active molecules, although proteolysis of high molecular weight DNA polymerase (109,000) has been shown by others to produce fragments of about 75,000 molecular weight. Either there is a naturally occurring polymerase protein of about 20,000 molecular weight, capable of aggregation with itself and with certain other molecules (e.g., exonucleases), or there are certain bonds in a large, native polymerase molecule that are especially susceptible to proteolysis without destroying activity.

Animals↗
PubMed1970

DNA--RNA.

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DNA↗
PubMed1970

A DNA-acrylamide gel column for analyzing proteins that bind to DNA. I. DNA polymerase.

A new procedure is described for purifying proteins that specifically bind to DNA. DNA is entrapped in polyacrylamide gel particles which can then be used in standard column chromatographic procedures. The method was developed using Escherichia coli DNA polymerase as the test material. The crude enzyme was applied at low ionic strength and eluted at high ionic strength with a 200-fold increase in specific activity on a single passage through the column. The method is versatile and simple and is not restricted to DNA-protein systems. Any macromolecule can be entrapped in the gel particles; these can interact with other large or small molecules in the liquid phase. The gel is stable at elevated temperatures and can therefore be used in hybridization experiments.

Acrylamides↗
PubMed1969

The negative control mechanism for E. coli DNA replication.

Evidence is presented to show that the initiation of DNA replication in E. coli 555-7 requires synthesis of a protein whose production is correlated with total protein synthesis. Once replication is initiated, however, reinitiation will occur if all further protein synthesis is prevented; a small amount of protein synthesis is sufficient to prevent this unregulated reinitiation. This shows that the initiation of DNA replication is under negative control. A mechanism for the control of DNA replication is proposed; in this mechanism a replication repressor is synthesized periodically, while an antirepressor protein is synthesized continuously. Derepression of initiation results after sufficient accumulation of the antirepressor protein, and repression is re-established by repressor synthesis after the initiation of replication.

Bacterial Proteins↗
PubMed1968

Shear and the melting of DNA: an especially sensitive portion of the E. coli genome.

The melting point of DNA is shown to be a function of shear stress. The higher the molecular weight of the DNA, the further its melting point is lowered by a given shear rate. During lysis of E. coli, a part of the DNA is especially shear sensitive, so that its melting curve in the presence of shear shows a low-melting region prior to the main transition. Lysis and dilution of the cell contents destroys the extra shear sensitivity, perhaps because the DNA dissociates from the cell membrane or from some other large subcellular structure. Such a structure would impart increased shear sensitivity to the associated region of the genome.

Chemical Phenomena↗