Ff01 571 72

Details of our experimental setup are described previously (Ganji et al., 2016a (link); Ganji et al., 2016b (link)). Briefly, a custom-made epifluorescence microscopy equipped with two lasers (532 nm, Samba, Cobolt and 640 nm, MLD, Cobolt) and an EMCCD camera (Ixon 897, Andor) is used to image fluorescently labeled DNA molecules. For the wide-field, epifluorescence-mode illumination on the sample surface, the two laser beams were collimated and focused at the back-focal plane of an objective lens (60x UPLSAPO, NA 1.2, water immersion, Olympus). Back scattered laser light was filtered by using a dichroic mirror (Di01-R405/488/543/635, Semrock) and the fluorescence signal was spectrally separated by a dichroic mirror (FF635-Di02, Semrock) for the SxO channel and Cy5 channel. Two band-pass filters (FF01-731/137, Semrock, for SxO) and FF01-571/72, Semrock, for Cy5) were employed at each fluorescence channel for further spectral filtering. Finally, the fluorescence was imaged on the CCD camera by using a tube lens (f = 200 mm). All the measurements were performed at room temperature.

Details of the experimental setup were described previously (27 (link),30 ). Briefly, an Olympus IX81 TIR microscope, equipped with a 60x oil-immersion objective (CFI APO TIRF, NA 1.49, Nikon), two lasers (532 and 640 nm; Cobolt), and a sCMOS camera (PrimeBSI; Teledyne Photometrics), was used to image RNAP–Alexa647, and DNA molecules via Sytox Orange (Thermo Fischer) intercalating dyes. Fluorescent emission was first filtered by a dichroic mirror (FF635-Di02; Semrock) and for the Sytox Orange and Alexa647 channels the band-pass filters FF01-731/137 (Semrock) and FF01-571/72 (Semrock) were used, respectively.