Comparison of semi‐dry and conventional tank‐buffer electrotransfer of proteins from polyacrylamide gels to nitrocellulose membranes

The rate of transfer of radiolabelled proteins from sodium dodecyl sulphate‐polyacrylamide gels to nitrocellulose membranes by semi‐dry blotting and electro‐transfer in a tank of buffer with and without sodium, dodecyl sulphate was quantitated. The semi‐dry blot method transferred about two thirds of most proteins in the first hour; less than one tenth of the total protein in the gel was transferred in the following hour. Conventional transfer in a tank of buffer without sodium dodecyl sulphate was dependent on the molecular weight and isoelectric point of the proteins. The efficient migration of high molecular weight and basic proteins required the presence of sodium dodecyl sulphate. The efficiency of transfer to the nitrocellulose depended both on the transfer method and on the pore size of the nitrocellulose. Almost all protein which left the gel could be accounted for when 0.1 μm pore size was used, but when 0.45 μm pore size was used in combination with semi‐dry blotting or transfer in a tank of buffer containing 0.1 % sodium dodecyl sulphate, less than 60 % of the protein could be accounted for after transfer. When transfers by two of the methods were compared using a mite extract as an antigen source and a group of miteallergic sera for detection, the same proteins were detected in each case but those which had been transferred by the semi‐dry blot method were more easily detected by the antisera used.