Can I prepare my protein sample with the reducing agent and store it for future use?
DTT is not stable, so it must be added and the reduction performed just prior to loading your samples.
Find additional tips, troubleshooting help, and resources within our Protein Gel 1D Electrophoresis Support Center.
My LDS or SDS sample buffer precipitates when stored at 4 degrees C. Can I warm it up? Can I store it at room temperature?
Precipitation of the LDS or SDS at 4 degrees C is normal. Bring the buffer to room temperature and mix until the LDS/SDS goes into solution. If you do not want to wait for it to dissolve, you can store the sample buffer at room temperature.
Find additional tips, troubleshooting help, and resources within our Protein Gel 1D Electrophoresis Support Center.
I used one of your protein standards for a western transfer and noticed that some of the lower-molecular weight protein bands passed through the membrane. How can I resolve this issue?
- Decrease voltage, current or length of transfer time
- Make sure that the methanol concentration in the transfer buffer is proper; use a methanol concentration of 10-20% methanol removes the SDS from SDS-protein complexes and improves the binding of protein to the membrane.
- Make sure that the SDS concentration (if added) in the transfer buffer is proper, don't use more than 0.02-0.04% SDS. Using too much SDS can prevent binding of proteins to the membrane.
- Check the pore size of the membrane and the size of the target protein. Proteins smaller than 10 kDa will easily pass through a 0.45 µm pore size membrane. If proteins smaller than 10 kDa are of interest, it would be better to use a 0.2 µm pore size membrane.
Find additional tips, troubleshooting help, and resources within our Protein Assays and Analysis Support Center.
I used one of your protein standards for a western transfer and noticed that some of the higher-molecular weight bands transferred very poorly to the membrane. Can you offer some tips?
- Increase voltage, current or length of time for transfer
- SDS in the gel and in the SDS-protein complexes promotes elution of the protein from the gels but inhibits binding of the protein to membranes. This inhibition is higher for nitrocellulose than for PVDF. For proteins that are difficult to elute from the gel such as large molecular weight proteins, a small amount of SDS may be added to the transfer buffer to improve transfer. We recommend pre-equilibrating the gel in 2X Transfer buffer (without methanol) containing 0.02-0.04% SDS for 10 minutes before assembling the sandwich and then transferring using 1X transfer buffer containing 10% methanol and 0.01%SDS.
- Methanol removes the SDS from SDS-protein complexes and improves the binding of protein to the membrane, but has some negative effects on the gel itself, leading to a decrease in transfer efficiency. It may cause a reduction in pore size, precipitation of some proteins, and some basic proteins to become positively charged or neutral. Make sure that the methanol concentration in the transfer buffer is not more than 10-20% and that high-quality, analytical grade methanol is used.
Find additional tips, troubleshooting help, and resources within our Protein Assays and Analysis Support Center.