Interaction of Cucurbituril Molecular Containers with the Aerolysin Nanopore for Molecular Recognition

Abstract

Cucurbit[n]urils (CBn) are molecular containers which form complexes with various guest molecules, such as amino acids and peptides. Here we report the ionic current block and reversible binding of different CBn of sizes n=5, n=6, n=7 and n=8 with the aerolysin (Ael) protein nanopore. CBn molecular containers enter the Ael nanopore exclusively from the extracellular cap domain and under a trans negative voltage. We attempt to relate differential effects of the electrolytes KCl, NaCl, CsCl and LiCl and of the ionic strength on the voltage-dependence of frequency and dwell-time. Notably, the current blockade frequency as well as the current blockade duration increase with increasing the magnitude of applied voltage. Our results suggest that CBn behave as positively charged molecular containers and trans negative voltage promotes their blocking the Ael pore lumen for up to several seconds. Our approach could be used for rapid and real-time probing of the abilities of different CBn to form host-guest complexes with various guest molecules.