Microrheology of Biopolymers at Non-thermal Regimes

Abstract

Many studies demonstrate the relevance of the mechanical properties of molecules and living cells to physiological function. Therefore, several techniques have been developed to probe the rheology of biological materials. Among them are based on the analysis of embedded probe fluctuations. However, novel applications using this robust tool are still lacking, despite the fact that the study of living matter routinely demonstrate new phenomena, not immediately characterized by existing analytical tools developed in physics. Hence, we derive novel robust tools to adapt ways of probing non-linear and non-equilibrium phenomena for biological samples. We propose designs of optical tweezer systems using two-beam tandems by dual-wavelength and single-wavelength splitting, for the study of microrheology in bulk down to single biopolymer or protein based on the fluctuation spectra of embedded or attached probes. We generalize, for the first time, calculations for winding turn probabilities to account for unfolding events in single fibrous biopolymers, which is modeled using a newly derived worm-like-chain model re-expressed by fractional strain expansion. The ensuing probe fluctuations are taken as originating from a damped harmonic oscillator. The approach described here offer new ways of characterizing biopolymer rheology using parameters based on folding turns and a newly derived WLC expansion for non-linear stretching.