Abstract

Many biological systems rely on fundamental physical principles for their proper function. A key example are mechanical processes such as force generation and adaptation of stiffness and viscosity that have been instrumental to explain complex biomedical questions with physical concepts. Such advances in understanding cell biology by physical approaches have been largely driven by new methods that allow to quantify biological processes and to construct theoretical models with high predictive power. I will present our recent approaches that allow to study active force generation and mobility in different cellular systems. Combining optical tweezer based cell mechanics measurements with precise particle fluctuation analysis, we demonstrate a tuning of intracellular mechanics during cell division. Using the same tools, we can furthermore define a mechanical fingerprint that allows to separate different cell types based on their intracellular active mechanics. While these approaches still require a high precision optical tweezer measurement, a new approach can yield the same information using a simple passive observation. Here we exploit the Onsager principle to extract the non-equilibrium energy that is injected in the system. We derive a new quantity, the mean back relaxation (MBR) which allow to extract more information from confined trajectories than a classical MSD .