PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “DNA, Circular”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMed1985

Formation of small circular DNA molecules via an in vitro site-specific recombination system.

The Cre-lox site-specific recombination system of bacteriophage P1 has been used to investigate the role of DNA flexibility in recombination. We have determined that a minimal distance of 82 bp must separate two loxP sites located on the same DNA molecule to allow these sites to undergo intramolecular recombination with one another. As a result of recombination, DNA circles as small as 116 bp have been produced. IN addition, we have demonstrated that the nuclease BAL 31 recognizes distortions in the DNA helix resulting from the formation of small DNA circles whose length is not a multiple of the helical repeat.

Base Composition↗
PubMed1997

Quantitation of ethidium-stained closed circular DNA in agarose gels.

The fluorescence of ethidium bromide (EB) bound to equimolar amounts of supercoiled form I and unstrained linear form III pBR322, SV40 and PM2 DNA in agarose gels has been measured by scanning a photographic negative of the gel with a microdensitometer. For SV40 and PM2 DNA, commonly used staining conditions cause both forms, i.e. linear and supercoiled, to fluoresce to the same extent. This obviates the need to use a correction factor for the fluorescence of form I DNA when measuring the amount of this form relative to the amounts of unstrained forms in agarose gels. In the case of PBR322 DNA, form I was found to fluoresce approximately 20% more than form III DNA.

Bacteriophages↗
PubMed1976

An enzyme system for replication of duplex circular DNA: the replicative form of phage phi X174.

Viral single strands (SS) are converted to the duplex from (RF) by a soluble enzyme fraction uninfected Escherichia coli [Schekman et al. (1975) J. Biol. Chem. 250, 5859-5865]. When reactions were supplemented with a soluble enzyme fraction from phi X174-infected cells, replication of phi X174 superhelical RF I DNA was observed. The activity supplied by infected cells was absent in cells treated with chloramphenicol or in cells infected with a phi X174 phage mutant in cistron A (cis A). A host function coded by the rep gene, essential in vivo for RF replication (but not for SS leads to RF), was supplied by enzyme fractions from either infected or uninfected cells. Based on complementation assays, the cisA-dependent and the rep-dependent proteins have each been purified about 1000-fold. The synthetic products of the enzymatic reaction were identified as RF I and RF II in which viral (+) and complementary (-) strands were newly synthesized.

Bacterial Proteins↗
PubMed1985

In vitro replication of duplex circular DNA containing the simian virus 40 DNA origin site.

Extracts (0.2 M NaCl) of HeLa cells support replication of DNA containing simian virus 40 (SV40) origin in the presence of SV40 large tumor (T) antigen. The reaction leads to the accumulation of high molecular weight products that represent DNA containing one parental strand and one progeny strand as well as duplex molecules that contain both strands derived from the input deoxynucleoside triphosphates. The replication reaction is inhibited by aphidicolin and by camptothecin, two inhibitors known to inhibit eukaryotic DNA replication in vivo.

Antigens, Viral, Tumor↗
PubMed1988

Effect of excluded volume on topological properties of circular DNA.

We have performed computer simulations of closed polymer chains with allowance for the excluded volume effects within the framework of the free-joint model. The probability of knot formation, the linking probability of a pair of chains and the variance in the writhing number proved to be significantly affected by the excluded volume effects. This is true even for DNA with completely screened charges for which the b/d ratio (where b is the Kuhn statistical length and d is the diameter of the double helix) is as large as 50. Allowance for the electrostatic repulsion (change of the DNA effective diameter d) further increases the effects. The most dramatic dependence on d is found for the probability of knot formation. The data on the dependence of the variance of writhing, mean value of (WR)2, on d indicate that the DNA superhelix energy should be significantly ionic strength-dependent. Special calculations have shown that the free-joint model underestimates the mean value of (Wr)2 value by about 20% as compared with the wormlike model.

DNA, Circular↗