Abstract
The thermal motion of charged proteins causes randomly fluctuating electric fields inside cells. According to the fluctuation–dissipation theorem, there is an additional friction force associated with such fluctuations. However, the impact of these fluctuations on the diffusion and dynamics of proteins in the cytoplasm is unclear. Here, we provide an order-of-magnitude estimate of this effect by treating electric field fluctuations within a generalized Langevin equation model with a time-dependent friction memory kernel. We find that electric friction is generally negligible compared to solvent friction. However, a significant slowdown of protein diffusion and dynamics is expected for biomolecules with high net charges such as intrinsically disordered proteins and RNA. The results show that direct contacts between biomolecules in a cell are not necessarily required to alter their dynamics.
Highlights
The cell is densely filled with proteins, RNAs, and metabolites.[1]
We studied the effects of long-range electrostatic forces on the diffusive dynamics of biopolymers
We obtained an analytical estimate of the magnitude of such field fluctuations and how these fluctuations impact the diffusion of a charged particle and the dynamics of a charged Rouse chain
Summary
The cell is densely filled with proteins, RNAs, and metabolites.[1]. Many studies in the past have investigated how the cellular interior affects the stability and dynamics of proteins.[2]. Previous simulations found a slowdown in the diffusion of a charged protein in the presence of charged cytosolic biomolecules.[11] charge−charge interactions can cause a nonspecific “sticking” of proteins to other cytosolic compounds, here we are concerned with a more general question: do electric field fluctuations caused by cytosolic macromolecules affect the diffusion of a charged particle? We derive an expression for the magnitude of the electrostatic force fluctuations and, using the model in which these fluctuations are described as colored noise with a finite correlation time, further derive an expression for the friction memory kernel. We use these results to estimate how electrostatic fluctuations affect the diffusion coefficients of charged particles. In section II.B, we include electric friction in a Rouse chain and study how it affects the chain reconfiguration time
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