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Discrimination between cysteine and homocysteine at the single-molecule level is achieved within a K238Q mutant aerolysin nanopore, which provides a confined space for high spatial resolution to identify the amino acid difference.

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The aerolysin nanopore displays a charming sensing capability for single oligonucleotide discrimination. When reading from the electrochemical signal, stronger interaction between the aerolysin nanopore and oligonucleotide represent prolonged duration time, thereby amplifying the hidden but intrinsic signal thus improving the sensitivity. In order to further understand and optimize the performance of the aerolysin nanopore, we focus on the investigation of the hydrogen bond interaction between nanopore, and analytes. Taking advantage of site-direct mutagenesis, single residue is replaced. According to whole protein sequence screening, the region near K238 is one of the key sensing regions. Such a positively charged amino acid is then mutagenized into cysteine and tyrosine denoted as K238C, and K238Y. As (dA) 4 traverses the pores, K238C dramatically produces a six times longer duration time than the WT aerolysin nanopore at the voltage of +120 mV. However, K238Y shortens the dwell time which suggests the acceleration of the translocation causing poor sensitivity. Referring to our previous findings in K238G, and K238F, our results suggest that the hydrogen bond does not dominate the dynamic translocation process, but enhances the interaction between pores and analytes confined in such nanopore space. These insights give detailed information for the rational design of the sensing mechanism of the aerolysin nanopore, thereby providing further understanding for the weak interactions between biomolecules and the confined space for nanopore sensing.

The identification and separation of chiral pesticides R/S-profenofos are of great significance due to different biological toxicity of chiral isomers. In the study, we designed two novel ligands: (2,2 0 :6 0 ,2 00 -terpyridin)-6-yl(5-methoxy-1H-pyrazol-1-yl) methanethione (TMMT) and (2,2 0 :6 0 ,2 00 -terpyridin)-6-yl(5-methoxy-1H-pyrazol-1-yl) methanone (TMMO), and taking them as ligands coordinated with uranyl, two novel complexes [Uranyl-TMMT] 2+ and [Uranyl-TMMO] 2+ as receptors were successfully constructed. The complexation and enantioselectivity of two receptors towards R/S-profenofos as guests