Elasticity of short DNA molecules: theory and experiment for contour lengths of 0.6-7 m.
Yeonee Seol, JILA
Jinyu Li, University of Colorado at Boulder
Philip Nelson, University of Pennsylvania
Thomas T. Perkins, University of Colorado, Boulder
M. D. Betterton, University of Colorado, Boulder
Keywords: DNA elasticity; force-extension behavior; optical trapping; single-molecule; stretching DNA; worm-like chain
DNA, the biomolecule that provides the blueprint for life, has a lesser-known identity as a stretchy polymer. The authors have found a flaw in the most common model for DNA elasticity, a discovery that will improve the accuracy of single-molecule research and perhaps pave the way for DNA to become an official standard for measuring picoscale forces, a notoriously difficult challenge.
The experiments described in this paper reveal that a classic model for measuring the elasticity of double-stranded DNA leads to errors when the molecules are short. For instance, measurements are off by up to 18 percent for molecules 632 nanometers long, and by 10 percent for molecules about twice that length. (By contrast, the DNA in a single human cell, if linked together and stretched out, would be about 2 meters long.)
The old elasticity model assumes that polymers are infinitely long, whereas the most popular length for high precision single-molecule studies is 600 nm to 2 microns, coauthor Tom Perkins says. Accordingly, several university collaborators developed a new theory, the finite worm-like chain (FWLC) model, which improves accuracy by incorporating three previously neglected e
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