1207.5725 (Hédi Soula et al.)

Anomalous versus non-homogeneous diffusion in the ligand-binding
equilibrium: when size matters    [PDF]

Hédi Soula, Bertrand Caré, Guillaume Beslon, Hugues Berry

Measurements of protein motion in living cells and membranes consistently report transient anomalous subdiffusion which converges back to a Brownian motion with reduced diffusion constant at long times, after the subdiffusion regime. On the other hand, membranes are also non-homogeneous media in which Brownian motion may be locally slowed-down due to variations in lipid composition. Here, we investigate whether both situations lead to a similar behavior for the reversible ligand-binding reaction in 2d. We compare the (long-time) equilibrium properties obtained with transient anomalous diffusion to those obtained with slowed-down Brownian motion. We show that both processes increase the apparent affinity of the reaction. However, in the case of slowed-down Brownian motion, the affinity is maximal when the slowdown is restricted to a subregion of the available space. Hence, these two processes are different: size matters for slowed-down Brownian motion, not for transient anomalous subdiffusion.

View original: http://arxiv.org/abs/1207.5725