(140c) Effect of Interaction Position on Molecular Transport and Separation through a Multi-Site Nanopore

Mass transport in confinement spaces like nanopores has become a field of interest for many applications such as separation employing membranes, microfluidic systems, chemical analysis, and drug delivery. This is due to the possibility of having efficient, fast, and robust separation in transport through one dimensional membranes and pores. This type of transport differs in many ways from bulk transport due to specific interactions between the pore and molecules when the pore dimension is around nanometer. Several studies are focused on mimicking the physical and chemical properties of biological pores that exhibit real example of enhanced separation through nanopores. However, a theoretical model that describes the role of the molecule-pore interaction in the molecular transport through channels has not been developed yet. Here, we develop a theoretical approach to explain the origin of separation efficiency in molecular transport through channels. 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 symmetry and the strength of the molecular-pore interactions are examined. The most efficient separation is predicted when the interaction site is located near the entrance to the nanopore. However, based on the amount of two limiting rate steps that are introduced in the model, changing the position of interaction to the middle of the pore can enhance the separation. In general, the selectivity is higher for large entrance rates into the channel. The origin of the results is discussed as well.