Real-Time Fluorescent Observation of DNA-Protein Interaction at the Single-molecule Level

Single-molecule direct observations have been studied by many researchers to reveal molecular behaviors usually hidden in the ensemble and time averaging of bulk experiments. In recent years, single-molecule analyses of various DNA-protein interactions by using florescent techniques were performed. In this study, single-molecule DNA hydrolysis by exonuclease III and lambda exonuclease were observed. We observed the DNA digestion of individual stretched DNA molecules from the free end. The shortening of fluorescently stained DNA was recorded and analyzed. The sequentially captured photographs demonstrate that the digested DNA molecule linearly shortened with reaction time. These observations were based on a simple experimental setup. A relationship between a physical form and biochemical reaction is very interesting. Single-molecule experiments should elucidate the mechanism of force-related DNA-protein interactions and provide additional insight into these interactions in living cells.