Team:HKUST/Protocols/Western blotting

Western Blotting

Procedure:

1. Yeast transformed cells containing appropriate plasmids were grown in SCM with appropriate amino acids deleted and harvested at a cell density corresponding to an OD600 of a 10-fold dilution reaching 0.2.
2. 2× Laemmli’s buffer (20% v/v glycerol, 0.1M Tris-HCl pH 6.9, 4% SDS, 0.2% bromophenol blue, 10% mercaptoethanol) was added and yeast crude extracts were prepared by glass bead lysis and separated on 10% SDS-PAGE.
3. The 10% resolving gel and the 5% stacking gel were cast according to the method described in Molecular Cloning (Sambrook et al., 1989).Separation was performed on a Mini Protean 3 gel and transblot system (Biorad). Proteins were stacked at 60-80 volts in the stacking gel and resolved at 120-150 volts in the resolving gel.
4. The proteins were then transferred onto a nitrocellulose membrane (pore size 0.45 μm, Schleicher &Schuell) in electrophoretic blotting system (C.B.S. Scientific) by applying a constant current of 0.5 mA for 1.5 hours.
5. After transferring, the membrane was taken out and socked in Ponceau S solution (0.5% Ponceau S in 1% HAc) for 1 min. After rinsed with ddH2O and labeled with protein marker bands.
6. The membrane was destained with TBST buffer (10 mM Tris-HCl pH8.0, 150 mM NaCl, 0.05% v/v Tween-20) and blocked with 5% milk in TBST for 30 min.
7. Then the membrane was incubated with the primary antibody (mouse monoclonal antibody against Flag) for 1 hour at room temperature followed by 3 × 15 min washing with TBST.
8. The membrane was then incubated with secondary antibody (goat anti-mouse antibody conjugated with horseradish peroxidase) for 1 hour at room temperature followed by 3 × 15 min washing with TBST.
9. After that, the membrane was incubated in SuperSignal chemiluminescence substrate (Pierce) for 5 min and exposed to light-sensitive films (Fuji). In the end, the film was developed in a film-processing machine (Eastman Kodak).

• Agarose gel preparation and gel electrophoresis
• PCR (Taq, Vent)
• PCR product clean-up
• Enzyme digestion (vector, insert)
• Plasmid DNA extraction
• Gel cutting
• Gel extraction
• Ethanol precipitation
• Ligation
• Transformation to E.coli
• Transformation to yeast
• Cell lysis
• Yeast genomic DNA extraction
• Western blotting
• GFP testing