Results 171 to 180 of about 7,352 (214)

Replication of Superhelical DNAs in Vitro

1986
Publisher Summary This chapter discusses purified systems that can replicate closed-circular, double-stranded superhelical (form I) DNAs in vitro . It also discusses problems unique to the replication of DNAs under topological constraint. Studies on the reconstituted pBR322 DNA replication system are used as a guide in the chapter. Recent studies on
K J, Marians, J S, Minden, C, Parada
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Prokaryotic DNA Ligases Unwind Superhelical DNA

Biochemical and Biophysical Research Communications, 1996
We have studied the effect on DNA topology of binding of prokaryotic DNA ligases (T4 and E. coli) to superhelical or nicked circular DNA. Performing topoisomerase I-mediated relaxation in the presence of increasing amounts of T4 ligase led to a shift in the topoisomer distribution to increasingly more negative values.
M, Ivanchenko, K, van Holde, J, Zlatanova   +2 more
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Electrostatic effects in short superhelical DNA

Biophysical Chemistry, 1994
We present Monte Carlo simulations of the equilibrium configurations of short closed circular DNA that obeys a combined elastic, hard-sphere, and electrostatic energy potential. We employ a B-spline representation to model chain configuration and simulate the effects of salt on chain folding by varying the Debye screening parameter.
M O, Fenley, W K, Olson, I, Tobias, G S, Manning   +3 more
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Energetics of superhelicity and of B-Z transitions in superhelical DNA

Cell Biophysics, 1987
The linking difference, alpha, imposed upon a superhelically constrained DNA molecule must be partitioned between twisting and bending deformations. Transitions to alternative secondary structures can occur at susceptible sites, altering the local molecular twist by an amount delta Twtrans.
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Effect of DNA superhelicity on transcription termination

Molecular and General Genetics MGG, 1987
Restriction fragments containing either leut (a rho-independent transcription termination site) and/or leut' (a rho-dependent transcription termination site) were cloned into plasmid pOL4. Treatment of plasmid-containing Escherichia coli strains with coumermycin resulted in loss of in vivo plasmid superhelicity 10 min after antibiotic addition ...
E R, Rosenthal, J M, Calvo
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Superhelicity and DNA Radiation Sensitivity

SAE Technical Paper Series, 1990
<div class="htmlview paragraph">Several underwound families of topoisomers of the plasmid pIB130 were irradiated with fission neutrons at 28 C in TE buffer. Form I DNA followed the expected exponential dependence on dose, and was greater for those DNA molecules characterized by larger linking numbers.
Charles E. Swenberg, Eric A. Holwitt, James M. Speicher   +2 more
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Geometry and mechanics of DNA superhelicity

Biopolymers, 1983
AbstractThis paper analyzes the elastic equilibrium conformations of duplex DNA constrained by the constancy of its molecular linking number, Lk. The DNA is regarded as having the mechanical properties of a homogeneous, linearly elastic substance with symmetric cross section.
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Alteration of superhelical state of DNA by aluminium (Al)

Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression, 1993
The effect of aluminium (Al) on the supercoiled state of pUC18 DNA was studied by ethidium bromide fluorescence and agarose gel electrophoresis. Al at physiologically relevant concentrations relaxed the intact supercoiled DNA as well as the topoisomers induced by chloroquine. EDTA prevented the unwinding effect of Al on supercoiled DNA.
K S, Rao, B S, Rao, D, Vishnuvardhan, K V, Prasad   +3 more
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Electron microscopy of superhelical circular λ DNA

Journal of Molecular Biology, 1968
Abstract Electron microscopy confirms that circular λ DNA molecules contain supertwists. The average number of primary supertwists at low ionic strength (0.06) is 117, or 3.8 per million molecular weight. This number is not constant but decreases to an average of 12 when the ionic strength is increased to 2.0.
V C, Bode, L A, MacHattie
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Thermodynamics of the B–Z transition in superhelical DNA

Nature, 1984
One of the most exciting events in recent years in molecular biology was the discovery of the left-handed Z form of the DNA double helix. Originally found in linear self-complementary d(GC)x . d(GC)x polymers and oligomers in non-physiological conditions (a rather high salt concentration), it was recently shown to be easily enough adopted in ...
M D, Frank-Kamenetskii, A V, Vologodskii
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