Biochemical Techniques and Instrumentation

5.3.2.3. Transfer

5.2.3.3. Transfer

The separated proteins are transferred from the gel to a membrane made of nitrocellulose or polyvinylidene difluoride (PVDF). The membrane is placed on top of the gel, and a stack of filter papers is placed on top of that. The entire stack is placed in a buffer solution which moves up the paper by capillary action, bringing the proteins with it.

Another method for transferring the proteins is called "electroblotting". It uses an electric current to pull proteins from the gel into the PVDF or nitrocellulose membrane. Protein binding is based upon hydrophobic interactions as well as charged interactions between the membrane and protein. Nitrocellulose membranes are cheaper than PVDF, but are far more fragile and do not stand up for repeated probings. The uniformity and overall effectiveness of transfer of protein from the gel to the membrane can be checked by staining the membrane with Coomassie or Ponceau S dyes.