DNA Protocols

Preparing Chemically Competent E. coli Cells

1. Inoculate 5-10mL LB with Top10 E. coli culture at 37oC shaking over night
2. Subculture 1mL of bacteria into 50mL LB at 37oC shaking until OD₆₀₀ is 0.4-0.6 (~2.5 hr)
3. Centrifuge the subculture at max for 20 min at 4oC
4. Resuspend pellet in 12.5mL cold CaCl2 (50mM, 15% glycerol)

Rehydrating Registry DNA

1. Add ddH2O (10μL) to appropriate well (will turn orange)/li>
2. Incubate at room temperature for 10 min
3. Transform cells with DNA (1μL)
Store plates in -20oC

Bacterial Transformation

1. Thaw 100μL of competent cells on ice right before use (do not thaw completely)
2. Add DNA (max 20μL) to cells, flick to mix, and ice for 30 min
3. Heat shock 2 min at 42°C
4. Ice 5 min
5. Add 250μL LB medium to each tube
6. Incubate 30-60 min at 37°C shaking (Kan is always 1h+)
7. Spin down (14,000 rpm for 2 min) and remove all supernatant except ~100μL
8. Resuspend, spread 50μL on antibiotic plate
Grow overnight in incubator at 37°C

Plasmid Miniprep (E. coli)

• Resuspension P1 = 50mM Tris HCl (pH 8), 10mM EDTA, 100μg/mL RNase A (keep on ice, 4°C)
• Lysis P2 = 200mM NaOH, 1% SDS
• Precipitation P3 = 3 M K Acetate (pH 5.5)
1. Transfer O/N to 2mL tube and pellet culture (spin at 14,000 rpm for 2 mins). Dump supernatant, and repeat for the rest of O/N.
2. Discard supernatant, resuspend pellet in P1 (300μL)
3. Quickly: Add P2 (300 μL), invert gently 2-3x. Add P3 (300 μL), invert gently 2-3x
4. Centrifuge at 14,000 rpm, 10mins, room temp
5. Without disturbing pellet, transfer supernatant to clean 1.5mL tube. Add isopropanol (650 μL). Wait 10 mins, room temp
6. Spin at 14,000 rpm for 10 mins at 4oC
7. Discard supernatant, add cold 70% etOH (500 μL)
8. Centrifuge at 14,000 rpm for 5 mins at 4oC
9. Carefully discard supernatant, dry pellet upside down
10. Resuspend in sterile ddH2O (~30 μL)