I ran Western Blot to detect Egr-1 protein from MC3T3 cell lines, but my blot has too much unspecific bands so I can't detect protein I want. Here is my work flow, the reagents I used, and my results. Please tell me what should I do to improve my western blot results. Thanks!
Add 200 μl of Trypsin/EDTA per well (I cultured the cells in a 6-well plate) and incubate the plate at 37oC for 5 mins for cell detachment. Add 500 μl of culture media (α-MEM) to inhibit Trypsin, collect the cell in a 1.5 ml eppendorf tube. Centrifuge at 12000 rpm/3 mins/Room temperature. Aspirate the media. Lyse the cell with 200 μl RIPA buffer + 2 μl Protease Inhibitor + 2 μl Phosphorylation Inhibitor. Mix by pipette and keep the mixture on ice for 20 minutes.Centrifuge at 12000 rpm/15 mins/4oC. Collect ~ 180 μl of supernatant and measure the protein concentration.Add loading dye and boil the protein for 20 minutes. Store the samples at -20oC. Make the polyacrylamide gel 10% based on the instruction in Molecular Cloning (Sambrook). Boil the samples for 20 minutes prior loading. Ran PAGE-SDS at 150V, 30 mA, 90 minutes.Transfer the protein from the gel to the nitrocellulose membrane by wet transfer techniques. Transfer at 100V, 400mA, 90 minutes, 4oC (I used ice to cool the transfer tank)Block the membrane by 5% skim milk for 2 hours at RT. Wash the membrane 3 times, each time 5 minutes with TBST after blocking. Incubate the membrane with primary antibody overnight at 4 degree(I used EGR1 15F7 rabbit monoclonal antibody of Cell Signalling, and β-Actin sc-47778 mouse monoclonal antibody of Santa Cruz as control). I dilute the primary antibody at 1:1000 ratio in TBST (5 μl in 5ml).Wash the membrane 3 times, each time 5 minutes with TBST prior secondary antibody incubating. I used Anti-Rabbit IgG HRP Conjugate W4011 and Anti-Mouse IgG HRP Conjugate W4021 of Promega. I dilute the secondary antibody at 1:2500 ratio in TBST (2 μl in 5ml). I incubate the membrane with secondary antibody for 90 minutes at RT.Wash the membrane 3 times, each time 5 minutes with TBST then I start protein detection. I used Immobilon Western Chemiluminescent HRP Substrate to detection. For β-actin, I exposed the membrane for 10 seconds. For Egr-1, I exposed the membrane up to 1 minutes. The expected sized of β-actin is 43kDA and of Egr-1 is 75kDA.I can get the β-actin bands (very clear) but I can't get the Egr-1 bands.
I add the membrane in the attachments. The dots in the Egr-1 file is the 70kDa marker.
Thank you for spending your precious time helping me! I really appreciate that.