Special research project

SFB 1027: Physikalische Modellierung von Nicht-Gleichgewichtsprozessen in biologischen Systemen

"Non-equilibrium" is a concept in physics and refers to a state of matter outside of it thermodynamic equilibrium. Most systems in nature are not in thermodynamic equilibrium because they are not in a steady state and are constantly or abruptly subject to an outflow or inflow of particles and energy. Virtually all dynamic processes in living cells consume energy in the form of ATP. Commonly referred to as "active" processes, they are manifestly non-equilibrium processes and include: Cytoskeleton reorganization, intracellular transport, cell migration, cell polarization, transmembrane ion transport, exocytosis or endocytosis, intracellular concentration oscillations, spikes, waves, etc. At the molecular level, ATP-consuming processes include polymerization of actin filaments and microtubules, molecular motor-driven transport along cytoskeletal filaments, ion transport across membranes by pumps, kinetic "proofreading" in protein synthesis and in T-cell receptor signal transduction, and many more. Finally, on a larger scale, aggregation and temporal evolution of protein and bacterial films, and tissue formation and remodeling. Active dynamical processes involve the cooperation of many particles, hence the importance of understanding collective effects that appear in the interaction of the constituents involved. In biological systems, the concept of pattern formation is ubiquitous, both at the macroscopic scale (e.g., during the development of organisms) and at the microscopic scale (e.g., in actin polymerization, the distribution of adhesive areas on the bacterial membrane, or inter- and intracellular concentration waves). Just as obviously the different states of water cannot be read from the properties of a single water molecule, it is clear that dynamic phenomena such as the formation of lamellipodia during cell migration cannot be understood on the basis of knowledge of properties of individual actin monomers, molecular motors, and nucleators alone. More than single-molecule information (identification, sequence, and structure) is needed to understand the emergence of cellular and subcellular functions. The identification, quantitative analysis and, most importantly, theoretical modeling of these cooperative, dynamic non-equilibrium phenomena are the central focuses of this SFB.