1. Anneal crRNA with tracrRNA
a. Add 1 µl of 100 µM caged crRNA with 1 µl of 100 µM tracrRNA in a PCR tube, both dissolved in duplex buffer (Integrated DNA Technologies, IDT)
b. Heat to 95°C in a thermocycler for 3 minutes, cool on benchtop for 5 minutes
c. Add 8 µl of duplex buffer (IDT) to make 10 µM cr/trRNA solution
2. Mix to form reaction solution containing Cas9 in complex with cr/trRNA
a. In a PCR tube, add 8 µl nuclease free water (NFW), add 1 µl of NEBuffer 3.1 (New England Biolabs, NEB), mix thoroughly by pipetting up and down 10 times
b. Add 0.5 µl of caged 10 µM cr/trRNA solution
c. Add 0.3 µl of 10 µM Cas9, thoroughly mix by pipetting up and down 10 times
d. Incubate at room temperature for 30 minutes to form Cas9-gRNA complex (RNP)
3. Cas9 cleavage reaction
a. Add 2 µl (~60 fmol) of purified target DNA generated from PCR, mix thoroughly
b. Transfer to thermocycler heated at 37°C
c. To activate vfCRISPR caged gRNA, keeping the PCR tube lid open, hold the illumination LED flashlight 10 cm above the tube for 30 seconds
d. Incubate at 37°C for variable amount of time (30 minutes reaches saturation)
e. To stop the reaction at a given time point, transfer to a 95°C heated thermocycler for 5 minutes
4. EMSA Readout
a. Mix 4 µl of reaction solution with 16 µl of NFW. Mix thoroughly then load all into a E-Gel™ EX Agarose Gel, 4% (Invitrogen)
b. Run gel for 10 minutes, visualize with SYBR® Gold channel in gel imager
5. Nucleic acid-only Readout
a. Add 1 µl of 10 mg/ml Proteinase K, mix thoroughly, incubate for 15 min at 55°C
b. Mix 4 µl of reaction solution with 16 µl of NFW. Mix thoroughly then load all into a E-Gel™ EX Agarose Gel, 4% (Invitrogen)
c. Run gel for 10 minutes, visualize with SYBR® Gold channel in gel imager