(Invited) Probing the Single Molecular Structural and Interactional Properties

Abstract

Single molecule study, where science and engineering met, applies the tools and measurement techniques of nanoscale physics and chemistry to generate remarkable new insights into how physical, chemical, and biological systems function. It permits direct observation of molecular behavior that can be obscured by ensemble averaging and enables the study of important problems ranging from the fundamental physics of electronic transport in single molecule junctions and biophysics of single molecule interactions, such as the energetics and nonequilibrium transport mechanisms in single molecule junctions and the energy landscape of biomolecular reactions, associated lifetimes, and free energy, to the study and design of single molecules as devices-molecular wires, rectifiers and transistors and high‐affinity, anti‐cancer drugs.In this talk, we present two of our recent researches using the legendary scanning probe microscope Dr. Stuart Lindsay and the Late Dr. Nongjian Tao pioneered. One studies the small molecule-DNA interactions electronically by STM-breakjunction measurements of site-specific intercalation of small molecules (coralyne) into a custom-designed 11-base-pair DNA duplex. The results show that a single molecule DNA electrical rectifier is realized and the coralyne-induced spatial asymmetry in the electron state distribution caused the observed rectification. The other study elucidated the in situ single-molecule interaction of heparan sulfate (HS) with antithrombin (AT) on the endothelial cell membrane surface under near-physiological conditions, especially the role of sulfate groups in specific binding sites of HS for AT, using AFM recognition imaging and dynamic force spectroscopy measurements.