Comparison of the measured phase diagrams in the force-temperature plane for the unzipping of two different natural DNA sequences
Department of Physics, Harvard University, 02138, Cambridge, MA, USA
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Accepted: 5 January 2005
Published online: 16 March 2006
In this work, we consider the critical force required to unzip two different naturally occurring sequences of double-stranded DNA (dsDNA) at temperatures ranging from 20 ° C to 50 °C, where one of the sequences has a 53% average guanine-cytosine (GC) content and the other has a 40% GC content. We demonstrate that the force required to separate the dsDNA of the 53% GC sequence into single-stranded DNA (ssDNA) is approximately 0.5 pN, or approximately 5% greater than the critical force required to unzip the 40% GC sequence at the same temperature. In the temperature range between 20 and 40 °C the measured critical forces correspond reasonably well to predictions based on a simple theoretical homopolymeric model, but at temperatures above 40 °C the measured critical forces are much smaller than the predicted forces. The correspondence between theory and experiment is not improved by using Monte Carlo simulations that consider the heteropolymeric nature of the sequences.
PACS: 87.14.Gg DNA, RNA – / 82.37.Rs Single molecule manipulation of proteins and other biological molecules – / 87.15.-v Biomolecules: structure and physical properties –
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag, 2006