There have been many attempts to understand the central principle of life mediated by DNA-protein interactions surrounding complex environments. Still, the mechanistic insight of individual protein functions has been lacking in traditional ensemble assays. Thus, techniques visualizing a single molecule have emerged to uncover the discrete roles of DNA-protein interactions and their biophysical properties. This paper will review the advances in single-molecule tools imaging long genomic DNA and their applications in studying dynamic protein interactions. We focus on the three representative techniques, including molecular combing, nanochannel confinement, and DNA curtain assays, which use fluid-driven force to elongate the individual DNA. We provide an integrated perspective and a direction for future use to those who want to observe single DNA molecules along with their cellular factor of interest and employ them for dissecting protein function.
