Wiki/Team:Warsaw/protocols

Purification of His_Z_alpha and His_Z_omega

Culture E. coli producer strain in 3 ml of liquid LB medium + kanamycin for 8 hours. Then use it to inoculate 200 ml of liquid LB medium + kanamycin supplemented with 0,5 mM IPTG and grow it overnight. In the morning spin down the culture (5000 RPM, 10 min, 4 deg. C). Resuspend the pellet in PBS buffer and disrupt cells by sonication. Spin down sonication mixture (13200 RPM, 10 min, 4 deg. C) and discard supernatant – purified protein is present in sonication debris. Resuspend it in sterile ice cold ddH2O and store at 4 deg. C.

Culture, induce and disrupt E. coli in the same way as to purify His_Z_alpha. The protein is present in supernatant (about 10% of total protein) and can be added to selection medium without further purification.

We use "Plasmid Mini" plasmid DNA isolation kit from A&A Biotechnology and follow the protocol of producer.

Keep the bacteria on ice during the procedure. Pour ca. 25 ml of bacteria into a falcon tube and spin in 4°C at 4 krpm, 8 min with prolonged acceleration and deceleration. Remove supernatant. The pellet mustn't run dry. You can pour another portion of bacteria onto it and spin again. After desired amount of bacteria in pellet is collected, add CaCl₂ in an amount of 10% of initial culture used for spinning. Suspend the pellet until no debris is visible on the bottom. Incubate 45 min on ice. Then spin 8 min at 4 kg and remove supernatant. Suspend the pellet in 3 ml CaCl₂ and divide into aliquots of 100 ul.

Add desired volume of DNA to the 100 ul. culture in eppendorf tube. Incubate 30 min on ice. Heat shock for 90 s at 42°C. Incubate 10 min on ice. Add 0.9 ml of culture medium and let the bacteria grow at 37°C.