The Effects of Tetramethylammonium Cation on Oligonucleotide Analysis with Aerolysin Nanopore

Abstract

Nanopore biosensors, as an extremely sensitive tool, are widely applied to single-molecule analysis. Compared with the commonly used α-hemolysin, aerolysin nanopore possess a narrower channel, which distributes the abundant charged residues in the lumen. We replaced the commonly used potassium cations (K + ) with tetramethylammonium cations (TMA + ) to explore the cation effects. Experimental results demonstrate that the blockage of oligonucleotides in the TMA + system is distinctly more considerable than that in K + system. In particular, the blockade currents of Poly(dA) 5 are very closed to 0 pA. In addition, the capture rate of oligonucleotides is distinctly increased, and it is speculated that amphipathic TMA + can enhance the affinity of aerolysin nanopore for oligonucleotides. Furthermore, the estimated effective charges (Z inside ) of oligonucleotides inside aerolysin nanopore in two solutions suggest that the screening of K + on Poly(dA) 3 , Poly(dA) 4 , and Poly(dA) 5 is more effective than that for TMA + . This report deepens our understanding of the effects of cations in electrolyte.