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BP: Fachverband Biologische Physik

BP 13: Statistical Physics of Biological Systems I (joint session DY/BP)

BP 13.11: Talk

Tuesday, March 19, 2024, 12:30–12:45, BH-N 334

Tensile elasticity of multi-state flexible chains and loops — •Geunho Noh and Panayotis Benetatos — Department of Physics, Kyungpook National University, Daegu, Republic of Korea

Polymer loop structure commonly appears in biological phenomena, such as DNA looping and DNA denaturation. When a chain forms a loop, its elastic behavior differs from that of an open chain due to the loss of entropy. In the case of reversible loop formation, interesting behavior emerges related to the multi-state nature of the conformations. In this study, we model a multi-state reversible loop as a looping Gaussian chain which can bind to form a loop, or a zipping Gaussian loop which can zip to form a double-stranded chain. For each model, we calculate the force-extension relations in the fixed-force (Gibbs) and the fixed-extension (Helmholtz) statistical ensembles. Unlike the single Gaussian chain or loop, the multi-level systems demonstrate qualitatively distinct tensile elasticity and ensemble inequivalence. In addition, we investigate a Gaussian necklace consisting of reversible alternating blocks of the chain and loop, and obtain the temperature-force phase diagram. The phase diagram implies a force-induced phase transition from a completely looped (denatured) state to a mixed (chains and loops) state.

Keywords: polymer loops; polymer elasticity; ensemble inequivalence; phase transition; DNA denaturation