Methanol is not required for PVDF membranes. However, since PVDF membranes possess a hydrophobic nature, they require pre-wetting with a solution containing methanol before the transfer process. Nitrocellulose membranes, unlike PVDF, require methanol in transfer buffers. This is because methanol helps to remove SDS from the gel during the transfer process. However, using methanol can potentially shrink the gel's pore size, which may limit the transfer of certain molecules.