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Updated: Jul 28, 2026
08:48
Stretching Short Sequences of DNA with Constant Force Axial Optical Tweezers
Published on: October 13, 2011
Stretching of single collapsed DNA molecules.
C G Baumann1, V A Bloomfield, S B Smith
1Department of Biochemistry, University of Minnesota, St. Paul, MN 55108, USA.
Biophysical Journal
|March 29, 2000
Summary
Trivalent cations like spermidine and hexaammine cobalt(III) alter DNA elasticity and condensation. These cations induce DNA unpacking and intramolecular attractions, influencing DNA
Area of Science:
- Biophysics
- Molecular Biology
- Polymer Physics
Background:
- DNA condensation is crucial for cellular processes.
- Understanding DNA elasticity under multivalent ion conditions is key.
Purpose of the Study:
- To investigate the elastic response of single DNA molecules under condensing conditions.
- To characterize DNA behavior during condensation induced by trivalent cations.
Main Methods:
- Utilized optical tweezers to probe single plasmid and lambda phage DNA molecules.
- Applied varying concentrations of spermidine and hexaammine cobalt(III) (CoHex).
Main Results:
- Observed decreased persistence length with increasing spermidine concentration.
- Identified distinct behaviors (stick-release, plateau) during stretching of condensed DNA.
- Quantified intramolecular attraction (0.083-0.33 kT/bp) and its dependence on cation type.
- Found CoHex induces stronger attraction than spermidine.
Conclusions:
- Trivalent cations significantly alter DNA elasticity and induce condensation.
- DNA condensation involves unpacking from coiled structures and intramolecular attractions.
- The transition to condensation is dependent on DNA extension and cation properties.
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