(449bs) Theoretical Investigation of Optimized Molecular Separation Across a Nanochannel Membrane

Separation is critically important in various technological, industrial, and medical applications. Although there are many experimental methods that allow to separate molecules, frequently they are expensive and not efficient. Recently, a new method of separation of chemical mixtures based on utilization of channels and nanopores has been proposed and successfully tested in several systems. However, mechanisms of selectivity in the molecular transport during the translocation are still not well understood. We develop a simple theoretical approach to explain the origin of selectivity in molecular fluxes through a nanochannel membrane. Our method utilizes discrete-state stochastic models that take into account all relevant chemical transitions. More specifically, we analyze channels with different binding sites employed for separating mixtures of two types of molecules. The effects of the postion and the strength of the molecular-pore interactions are examined. It is found that the most efficient separation is predicted when the specific binding site is located near the entrance to the nanopore. In addition, the selectivity is higher for large entrance rates into the channel. It is also found that the molecular transport is more selective for repulsive interactions than for attractive interactions. The physical-chemical origin of the observed phenomena is discussed.