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We derive the equation of state of DNA under tension that features a loop. Such loops occur transiently during DNA condensation in the presence of multivalent ions or permanently through sliding protein linkers such as condensin. The force-extension relation of such looped-DNA modeled as a wormlike chain is calculated via path integration in the semiclassical limit. This allows us to rigorously determine the high stretching asymptotics. Notably the functional form of the force-extension curve resembles that of straight DNA, yet with a strongly renormalized apparent persistence length. We also present analogous results for DNA under tension with several protein-induced kinks and/or loops. That means that the experimentally extracted single-molecule elasticity does not necessarily only reflect the bare DNA stiffness, but can also contain additional contributions that depend on the overall chain conformation and length.
Kulić, I. M., Mohrbach, H., Thaokar, R., & Schiessel, H. (2007). Equation of State of Looped DNA. Retrieved from https://repository.upenn.edu/physics_papers/169
Date Posted: 18 May 2011
This document has been peer reviewed.