Fastscan a probes

All dry and fluid samples were imaged using the Dimension FastScan Bio Atomic Force Microscope (Bruker) in tapping mode.
For dry imaging, FastScan A probes (Bruker) with a spring constant of 18 N/m were tuned to a resonance frequency between 800 and 2,000 kHz and the amplitude setpoint was adjusted to the highest possible setting, so as to ensure little noise and minimizes the force the sample is exposed to. In fluid, FastScan D probes were used, with a spring constant of 0.25 N/m (resonance frequency of 90 to 140 kHz).
Fast-scan images were captured with a scan area of 1 to 2 µm, a scan rate of 15.1 Hz, and with 512 samples per line. For conventional AFM, images were captured at 1.8 frames per minute at room temperature.
Rad50 coiled-coil interactions with the DNA substrate during fast-scan imaging in fluid, as presented in Fig. 4A, were identified manually using similar interactions observed from AFM imaging in air data (Fig. 3) as a reference; see SI Appendix for further details.
All AFM images presented, excluding Fig. 6C, were processed using the Nanoscope Analysis software version 1.5 by Bruker Corporation. Fig. 6C was processed using SPIP software. Movies were produced using Windows Movie Maker.