FIGURE 5: Single molecule DNA nanomanipulation. (A) Extension vs. supercoiling curve for a single tethered DNA molecule. A schematic diagram of the magnetic trap is provided, showing a pair of trapping magnets located above a coverslip-bound DNA molecule tethered at one end to a magnetic bead. (B) Real-time detection of transcription. A succession of three states (RNAP-promoter open complex, RPo; RNAP-promoter initially-transcribing complex, RPitc; and RNAP-DNA elongation complex, RDe) can be identified corresponding to the different stages of transcription. RPo is oftentimes too short-lived to be observed in the presence of high concentrations of nucleotides, as RNAP can begin transcribing in those conditions. The initial baseline state, in which no RNAP is actively unwinding the DNA, is recovered upon transcription termination once the RDe complex reaches the transcription termination sequence and is ejected from the DNA.