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Measurement of the salt-dependent stabilization of partially open DNA by Escherichia coli SSB protein.

Hatch K, Danilowicz C, Coljee V, Prentiss M - Nucleic Acids Res. (2007)

Bottom Line: The rezipping force of two complementary DNA strands under tension has been measured in the presence of Escherichia coli single-stranded-binding proteins under salt conditions ranging from 10- to 400 mM NaCl.The effectiveness of the binding protein in preventing rezipping is strongly dependent on salt concentration and compared with the salt dependence in the absence of the protein.For salt concentrations greater than 200 mM NaCl, the protein inhibits rezipping but cannot block rezipping when the tension is reduced below 6 +/- 1.8 pN.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Harvard University, Cambridge, MA 02138, USA.

ABSTRACT
The rezipping force of two complementary DNA strands under tension has been measured in the presence of Escherichia coli single-stranded-binding proteins under salt conditions ranging from 10- to 400 mM NaCl. The effectiveness of the binding protein in preventing rezipping is strongly dependent on salt concentration and compared with the salt dependence in the absence of the protein. At concentrations less than 50 mM NaCl, the protein prevents complete rezipping of lambda-phage on the 2-s timescale of the experiment, when the ssDNA is under tensions as low as 3.5 +/- 1 pN. For salt concentrations greater than 200 mM NaCl, the protein inhibits rezipping but cannot block rezipping when the tension is reduced below 6 +/- 1.8 pN. This change in effectiveness as a function of salt concentration may correspond to salt-dependent changes in binding modes that were previously observed in bulk assays.

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Fz/Fu from both experiments (triangles) in the absence of protein and simulation (circles) as a function of salt. The solid line is the ratio expected from theory based on the salt dependence of ssDNA persistence length and the salt dependence of enthalpy.
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Figure 3: Fz/Fu from both experiments (triangles) in the absence of protein and simulation (circles) as a function of salt. The solid line is the ratio expected from theory based on the salt dependence of ssDNA persistence length and the salt dependence of enthalpy.

Mentions: The stability of naked DNA is known to be salt dependent (1–3) and thus it is necessary to separate the effects of DNA salt dependence and protein salt dependence in this experiment. In the absence of protein, Fz is measured as a function of salt, shown in Figure 3, where the Fz is normalized by Fu, to remove bead variation.Figure 3.


Measurement of the salt-dependent stabilization of partially open DNA by Escherichia coli SSB protein.

Hatch K, Danilowicz C, Coljee V, Prentiss M - Nucleic Acids Res. (2007)

Fz/Fu from both experiments (triangles) in the absence of protein and simulation (circles) as a function of salt. The solid line is the ratio expected from theory based on the salt dependence of ssDNA persistence length and the salt dependence of enthalpy.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2248746&req=5

Figure 3: Fz/Fu from both experiments (triangles) in the absence of protein and simulation (circles) as a function of salt. The solid line is the ratio expected from theory based on the salt dependence of ssDNA persistence length and the salt dependence of enthalpy.
Mentions: The stability of naked DNA is known to be salt dependent (1–3) and thus it is necessary to separate the effects of DNA salt dependence and protein salt dependence in this experiment. In the absence of protein, Fz is measured as a function of salt, shown in Figure 3, where the Fz is normalized by Fu, to remove bead variation.Figure 3.

Bottom Line: The rezipping force of two complementary DNA strands under tension has been measured in the presence of Escherichia coli single-stranded-binding proteins under salt conditions ranging from 10- to 400 mM NaCl.The effectiveness of the binding protein in preventing rezipping is strongly dependent on salt concentration and compared with the salt dependence in the absence of the protein.For salt concentrations greater than 200 mM NaCl, the protein inhibits rezipping but cannot block rezipping when the tension is reduced below 6 +/- 1.8 pN.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Harvard University, Cambridge, MA 02138, USA.

ABSTRACT
The rezipping force of two complementary DNA strands under tension has been measured in the presence of Escherichia coli single-stranded-binding proteins under salt conditions ranging from 10- to 400 mM NaCl. The effectiveness of the binding protein in preventing rezipping is strongly dependent on salt concentration and compared with the salt dependence in the absence of the protein. At concentrations less than 50 mM NaCl, the protein prevents complete rezipping of lambda-phage on the 2-s timescale of the experiment, when the ssDNA is under tensions as low as 3.5 +/- 1 pN. For salt concentrations greater than 200 mM NaCl, the protein inhibits rezipping but cannot block rezipping when the tension is reduced below 6 +/- 1.8 pN. This change in effectiveness as a function of salt concentration may correspond to salt-dependent changes in binding modes that were previously observed in bulk assays.

Show MeSH
Related in: MedlinePlus