Isoelectric Focusingof Serum Proteinson ModifiedThin Cellulose- Acetate Membranes

We applied a method previouslydescribed fortreating cellulose acetate gel strips with boron trifiuoridein methanol, tomake them suitableforisoelectricfocusing of proteins, to dry cellulose acetate membranes. The re-sults obtained are shown to compare very favorably. Both wide and narrow pH gradientsmay be used and coupled either to conventional protein stainingor to specific identificationby immunofixation.Focusing ordinarilytakes 90-120 mm, is technically easy, and is economical in the use of ampholytes. Despite the obvious advantages, few reports deal with successful isoelectric focusing of proteins on cellulose acetate membranes. Probable reasons for this include the high elec-tro-endosmotic flow that occurs in many of the commercial materials and the distortedpH gradients caused by rapid evaporation ofwater from thin membranes. Methylation of celluloseacetate gel membranes (Cellogel; Whatman Lab. Sales Ltd.,Maidstone, U.K.) with boron tn-fluoridein methanol produces a material suitablefor iso-electricfocusing of proteins (1). Ordinarily, Cellogel mem-branes are supplied immersed in methanol/water (30/70 by vol) and there is only one preliminary step: directly transfer-ring them to undiluted methanol. Non-gel membranes such as Sepraphore III (Gelman l-lawksley Ltd., Northampton, U.K.) will not tolerate this treatment without distortion, but they may be more gradually processed by taking them through a seriesof aqueous solutionsof increasingmethanol concen-tration. Here, we report the use of such modified material for iso-electricfocusingof proteinsand compare the use ofdry and gelmembranes forthispurpose