Results 161 to 170 of about 11,225 (206)

Superhelical DNA liquid crystals from dendrimer-induced DNA compaction

Soft Matter, 2021
Electrostatic compaction of dsDNA induced by a positively charged poly(amidoamine) dendrimer (PAMAM) of generation four produced two unique types of DNA mesophases, in which the DNA bent into superhelices packed in a tetragonal or hexagonal lattice.
Bradley W. Mansel, Chun-Jen Su, Chun-Yu Chen, Chih-Mei Young, Yen-Chih Huang, Cheng-Che Yang, Hsin-Lung Chen   +6 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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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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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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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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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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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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Superhelical Escherichia coli DNA: Relaxation by coumermycin

Journal of Molecular Biology, 1978
Abstract Folded chromosomes isolated from Escherichia coli strains after treatment with coumermycin A 1 in vivo , an inhibitor of DNA gyrase (Gellert et al. , 1976 a,b ), were found to have reduced DNA superhelical densities. This loss of DNA supercoiling paralleled inhibition of DNA synthesis.
K, Drlica, M, Snyder
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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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Superhelical DNA-dependent ATPase from calf thymus

Biochemical and Biophysical Research Communications, 1985
Two physically and catalytically distinct DNA-dependent ATPases were isolated from a purified preparation of calf thymus poly(ADP-ribose) polymerase. A unique feature of these two ATPases was the high stimulation by supercoiled DNA. Other nucleic acids (including denatured DNA and ribosomal RNA) and certain polynucleotides differentially stimulated the
P, Zahradka, K, Ebisuzaki
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