Sawtooth patterns in biomolecules force-extension curves: an equilibrium-statistical-mechanics theory

Abstract

We analyze the force-extension curve for a general class of systems, which are described at the mesoscopic level by a free energy depending on the extension of its components. Similarly to what is done in real experiments, the total length of the system is the controlled parameter. This imposes a global constraint in the minimization procedure leading to the equilibrium values of the extensions. As a consequence, the force-extension curve has multiple branches in a certain range of forces. The stability of these branches is governed by the free energy: there are a series of first-order phase transitions at certain values of the total length, in which the free energy itself is continuous but its first derivative, the force, has a finite jump. This behavior is completely similar to the one observed in real experiments with biomolecules like proteins, and other complex systems.

5 pages, accepted for publication in Phys. Rev. E

References in corpus (4)

• Single-molecule derivation of salt dependent base-pair free energies in DNA
• Recovery of free energy branches in single molecule experiments
• Hysteresis and nonequilibrium work theorem for DNA unzipping
• Spin-oscillator model for DNA/RNA unzipping by mechanical force

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• Protein unfolding and refolding as transitions through virtual states
• Relevance of the speed and direction of pulling in simple modular proteins
• Modelling the unfolding pathway of biomolecules: theoretical approach and experimental prospect
• Buckling in a rotationally invariant spin-elastic model