Immobilizing a single DNA molecule at the apex of AFM tips through picking and ligation

A proper surface treatment of the substrate and the AFM tip with a structured molecule provided a new approach to pick a single DNA molecule with reasonable success rate (75%) by AFM. Picking a single molecule by AFM tip and realizing the single interaction will likely be useful for single molecule dynamic force spectroscopy, because it avoids the formation of problematic multiple interactions. As an extension, a new single DNA was allowed to hybridize with the picked DNA, and conjugated with the picker DNA by use of a ligase. The attachment of a single DNA at the apex was confirmed by measuring the force between the new DNA and the complementary DNA on the generic surface. Various applications of the tip for manipulating single molecules and preparing new nanomaterials are envisaged.