Single-molecule analysis of lead(II)-binding aptamer conformational changes in an alpha-hemolysin nanopore, and sensitive detection of lead(II)

摘要

The alpha-hemolysin (alpha HL) nanopore is capable of analyzing DNA duplex and DNA aptamer as they can be electrophoretically driven into the vestibule from the cis entrance. The current study describes the competitive interaction induced by Pb2+ that changes the secondary structure of DNA duplex in asymmetrical electrolyte solution. DNA duplex formed by the partial complementary DNA and DNA aptamer sequence produced unzipping blockages with the dwell unzipping time lasting 2.84 +/- A 0.7 ms. By cation-DNA interaction with Pb2+, the DNA duplex will unwind and then form Pb2+-stabilized-DNA aptamer, which will be captured and unfolded in vestibule. The pore conductance were reduced to 54 % and 94 % with mean dwell unfolding times of 165 +/- A 12 ms. The competitive behavior between Pb2+ and single-strand DNA was further utilized to detect Pb2+ in solution with a detection limit of 0.5 nM. This nanopore platform also provides a powerful tool for studying the cation-DNA interactions in DNA aptamer conformational changes. Thus, the results drawn from these studies provide insights into the applications of alpha-hemolysin nanopore as a molecular sieve to different DNA secondary structure in future application of nanopore analysis.