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Inferring the Diameter of a Biopolymer from Its Stretching Response

Ngo Minh Toan ^* , Davide Marenduzzo   and Cristian Micheletti ^*

^* International School for Advanced Studies (S.I.S.S.A.) and the Istituto Nazionale Fisica della Materia, 34014 Trieste, Italy; Institute of Physics, Hanoi, Vietnam; The Rudolf Peierls Centre for Theoretical Physics, Oxford University, Oxford OX1 3NP, United Kingdom; and Mathematics Institute, University of Warwick, Coventry CV4 7AL, United Kingdom

Correspondence: Address reprint requests to Davide Marenduzzo, Oxford University, 1 Keble Road, OX1 3NP Oxford, UK. Fax: 44-0-1865-273947; E-mail: davide{at}thphys.ox.ac.uk, or davide{at}maths.warwick.ac.uk.

We investigate the stretching response of a thick polymer model by means of extensive stochastic simulations. The computational results are synthesized in an analytic expression that characterizes how the force versus elongation curve depends on the polymer structural parameters: its thickness and granularity (spacing of the monomers). The expression is used to analyze experimental data for the stretching of various different types of biopolymers: polypeptides, polysaccharides, and nucleic acids. Besides recovering elastic parameters (such as the persistence length) that are consistent with those obtained from standard entropic models, the approach allows us to extract viable estimates for the polymers diameter and granularity. This shows that the basic structural polymer features have such a profound impact on the elastic behavior that they can be recovered with the sole input of stretching measurements.