Can methanol in transfer buffer be replaced by a less toxic alternative?

Alcohol is a standard component of transfer buffer. 

Why is it used? The role of alcohol in the transfer buffer is to remove SDS from proteins, to allow their binding to the membrane, and prevent the gel from swelling during transfer (for SDS-PAGE gels). The alcohol will improve protein binding to the membrane, in case of PVDF (nitrocellulose membranes do not require activation with alcohol).

What is the alcohol concentration?
10-20 % methanol, or the safer alternative, ethanol.

Can different types of transfer be performed with ethanol?
Yes, both, semi-dry and wet transfer can be performed with ethanol in the transfer buffer.

Can alcohol be omitted completely from the transfer buffer?
Yes, methanol and ethanol can be omitted from the transfer buffer in specific conditions, like: use of nitrocellulose membrane and a modern gel system, like Bis-Tris based, designed for low swelling and high resolution gel electrophoresis. Please note that the protein transfer, in such a case, has to be conducted in the cold, as there is a risk for increased heat generation without alcohol in the transfer buffer. HMW proteins do not require alcohol for transfer to the same extend as LMW proteins do.

Can isopropanol be used in the transfer buffer?
Yes, however it is only slightly less toxic, compare to methanol, and may reduce protein transfer due to lower polarity, compared to methanol and ethanol. It is not well-characterized in published protocols.