Physics of actin : facts and ideas on self-assembly, non-thermal fluctuations, and chiral crystalization

The physics of actin provides a good illustration of how living matter can be taken as an interesting playground for soft matter physics. In the past 20 years, starting from seminal observations that semiflexibility leads to specific scaling exponents of the dynamics (PRL, 1996, 77, 470-73), we studied a few problems. I will first focus on out-of-equilibrium actin dynamics studied by multiple light scattering, to show how chemically controlled mechanical activity at the molecular scale, leads to high temperature longitudinal fluctuations with a caracteristic scaling exponent, and to the molecular time-scale of the molecular activity (PRL, 2002, 88, 018101). I will then describe experimental and theoretical results on the kinetic and geometric control of actin monomer self-assembly (Biophys J, 1999, 76, 1580-90; Nanoletters, 2011, 11, 5443-8). The effects of chirality and its frustration will be discussed in the context of actin polymer crystalization into an unexpected 3D crystal structured like a columnar liquid crystal (PRL, 2013, 110, 048102).