Semi-dry electroblotting of DNA

A procedure is described for the rapid transfer of DNA from agarose gels to nylon membranes using the semi-dry electroblotting technique. A Hind III digest of lambda DNA which was separated in a 1% agarose gel containing Tris, Borate, and EDTA (pH 8.0) was employed for the electrotransfer experiments. Transfer efficiency was determined by staining the DNA on the nylon membranes with a colloidal iron reagent. Current densities of 3-5 mA/sq. cm of gel permitted the transfer of high (23 kb) and low (0.3 kb) molecular weight fragments within 15 min. However, efficient transfer required a high ionic strength buffer that would prevent uneven dehydration of the agarose gel. Critical parameters for the transfer of nucleic acids with the semi-dry technique are discussed.