After running SDS, why soak the gel and membrane in a solution with methanol?

PVDF membrane should be activated with methanol before use, the purpose of which is to activate the positive electron group on the PVDF membrane, so that it is easier to bind to negatively charged proteins. Since small molecule proteins are not easy to bind to membranes and large molecules are easier, when they are transferred, adding more or no methanol is also for this purpose. Many people first use 100% methanol to soak the PVDF membrane for 10-15S, after the film from opaque to translucent, adding methanol-free transfer buffer, so that the final concentration of methanol is 20%, and then the membrane and the gel together soaked for 20-30min, we have directly soaked the gel with PVDF membrane with a transfer buffer containing 20% methanol for 30min, the results have not been affected.

Methanol can activate the charge on the PVDF membrane and make the membrane transfer more fully. Moreover, PVDF without methanol immersion is difficult to be infiltrated by the membrane transfer buffer