<scp><b>Single‐Molecule</b></scp> Measurement of Carbonic Anhydrase in Cation Coordinated Environment Using <scp><b>MspA</b></scp> Nanopore<sup>†</sup>
Dandan Song, Yunjiao Wang, Shaoxia Zhang, Lingyu Zhao, Linyu Gong, Liyuan Liang, Liang Wang
Abstract
Comprehensive Summary Carbonic anhydrase accounts for catalytic reaction of CO 2 /HCO 3 – transformation, thus resulting in neutralization and acidification of the cellular environment, thereby favoring tumor development. Hence, it is a classical protein model of greatly biocatalytic significance as well as a highly expressed biomarker with renal tumor. We herein proposed a single‐molecule measurement on carbonic anhydrase using MspA nanopore, in [BMIM + ] and asymmetric K + /Ca 2+ cationic coordinated environment, instead of usual symmetric KCl/NaCl electrolyte. Significantly, our empirical analysis showed that asymmetric K + /Ca 2+ cationic environment contributes to distinguishable current modulations, thus yielding better resolution for carbonic anhydrase measurement, which is independent of applied voltage and more importantly, is stable enough at varied pH conditions and for very low concentration test in urine sample. Our results provide a classical model for nanopore protein analysis, and may also permit biocatalytic measurement at single‐molecule level.