Anomalously slow transport in single-file diffusion with slow binding kinetics

We computationally study the effects of binding kinetics to the channel wall, leading to transient immobility, on the diffusive transport of particles within narrow channels, that exhibit single-file diffusion (SFD). We find that slow binding kinetics leads to an anomalously slow diffusive transport. Remarkably, the scaled diffusivity $\hat{D}$ characterizing transport exhibits scaling collapse with respect to the occupation fraction $p$ of sites along the channel. We present a simple "cage-physics" picture that captures the characteristic occupation fraction $p_{scale}$ and the asymptotic $1/p^2$ behavior for $p/p_{scale} \gtrsim 1$. We confirm that subdiffusive behavior of tracer particles is controlled by the same $\hat{D}$ as particle transport.

Spencer G. Farrell, Andrew D. Rutenberg · 2018