SFB 1027: Physical Modelling of Non-Equilibrium Processes in Biological Systems

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Non-equilibrium” is a concept from physics and denotes a state of matter out of thermodynamic equilibrium. Most systems found in nature are not in thermodynamic equilibrium because they are not in stationary states and are continuously and discontinuously subject to flux of matter and energy to and from the systems. Nearly all dynamical processes occurring in living cells consume energy in the form of ATP. Commonly de-noted as “active” processes they are manifestly out-of-equilibrium and include cytoskeleton reorganization, intracellular transport, cell migration and polarization, ion transport across membranes, exocytosis and en-docytosis, calcium oscillations, spikes and waves, and more. On the molecular level ATP consuming pro-cesses include polymerization of actin filaments and microtubules, molecular motor driven transport along cytoskeletal filaments, ion transport across membranes with pumps, kinetic proofreading in protein synthe-sis and T cell receptor signal transduction, and many more. Finally, on a larger scale the aggregation and temporal evolution of protein and bacterial films and tissue formation and remodeling. Active dynamical processes involve the cooperation of many particles, which is why the understanding of collective effects emerging in the interplay of the participating constituents is important. In biological systems the concept of pattern formation is abundant on macroscopic (e.g. during development) as well as on microscopic levels (e.g. actin polymerization, the distribution of adhesive patches on the bacterial cell wall or inter- and intra-cellular calcium waves). As it is obvious that the different phases of water cannot be read off from the properties of a single water molecule alone, it is clear that dynamical phenomena like the formation of lamel-lipodia during cell migration cannot be understood on the basis of individual actin-monomers, molecular motors and nucleators alone. One needs more than the single molecular information (identification, se-quence and structure) to understand the emergence of cellular and subcellular functions, and the identifica-tion, quantitative analysis and theoretical modeling of these cooperative dynamical non-equilibrium phe-nomena, are the central foci of this CRC.