Force-spectroscopy measurements were obtained using a custom-built AFM
instrument.30 (link) Automation routines to
control the AFM31 (link) were implemented in
LabView (National Instruments, Austin, Texas). Calibration of cantilever spring constants
were done in the buffer solution using the energy equipartition theorem.32 All measurements were performed in a PBS pH
7.4 solution at room temperature. Force spectroscopy experiments were performed using
pulling rates of 50, 300, 1500, and 3000 nm/s using MLCT cantilevers (Bruker, Camarillo,
CA) with the spring constant that varied between 16 and 150 pN/nm. In all experiments the
purified protein was diluted to ~100 µg/mL in PBS and applied to recently
evaporated gold and then incubated for an hour. A worm-like chain (WLC) model33 with persistence length of 0.4 nm was fit to
each peak in order to measure contour length increments in the force–extension
(FE) data.
instrument.30 (link) Automation routines to
control the AFM31 (link) were implemented in
LabView (National Instruments, Austin, Texas). Calibration of cantilever spring constants
were done in the buffer solution using the energy equipartition theorem.32 All measurements were performed in a PBS pH
7.4 solution at room temperature. Force spectroscopy experiments were performed using
pulling rates of 50, 300, 1500, and 3000 nm/s using MLCT cantilevers (Bruker, Camarillo,
CA) with the spring constant that varied between 16 and 150 pN/nm. In all experiments the
purified protein was diluted to ~100 µg/mL in PBS and applied to recently
evaporated gold and then incubated for an hour. A worm-like chain (WLC) model33 with persistence length of 0.4 nm was fit to
each peak in order to measure contour length increments in the force–extension
(FE) data.
