Single-molecule DNA digestion in various alkanethiol-functionalized gold nanopores

This paper presents the alkanethiol-functionalized environmental effects of individual DNA molecules in nanopores on enzyme digestion at the single-molecule level. A template consisting of gold deposited within a solid-state nanoporous polycarbonate membrane was used to trap individual λ-DNA and enzyme molecules. The gold surfaces were modified with various functional groups (–OH, –COOH, –NH3). The enzyme digestion rates of single DNA molecules increased with decreasing nanopore diameters. Surprisingly, the digestion rates in the l-cysteine chemisorbed nanopores were 2.1–2.6 times faster than in the mercaptoethanol chemisorbed gold nanopores, even though these nanopores had equivalent interspacial areas. In addition, the membrane of chemisorbed cysteamine with ionized functional groups of H3N+ at pH 8.2 had a greater positive influence on the enzyme digestion rate than the membrane of chemisorbed mercaptoproponic acid with ionized carboxyl groups (COO-). These results suggest that the three-dimensional environment effect is strongly correlated with the functional group in confined nanopores and can significantly change the enzyme digestion rates for nanopores with different internal areas.