Molecular Motors -- An Example of Teenage Thermodynamics: Not Quite Micro, Not Quite Macro
Bjarne Andresen
Niels Bohr Institute, University of Copenhagen
Abstract
Some of the most interesting processes occur at the mesoscale, somewhere between the microscopic
world of atoms and molecules and the macroscopic world we live in. Interesting not least because the organelles
of all living organisms operate precisely in this regime. Two types of mesoscope mechanisms are ratchets and
molecular motors. A ratchet is in principle just a periodic energy surface which has become directional by the
addition of random motion, shaking. Our muscle filaments are a prime example of this. Molecular motors similarly
convert one form of energy or concentration gradient into another through Brownian motion. Maintaining pH gradients
across cell membranes at the expense of ATP is an example here. Curiously this strictly chemical connection is
mediated by a real mechanical rotation within the membrane. The colloquium will present this mesoscopic realm,
discuss which statistical mechanical tools are appropriate for describing these processes, and in particular how
one may define their thermodynamic efficiency.
