Isoelectric focusing of beta-lactamases on cellulose acetate membranes

Cellulose acetate membranes treated with boron trifluoride in methanol were found to provide suitable support material for isoelectric focusing of beta-lactamases; the method used is described. A linear pH gradient was obtained and the application of visible pI markers allowed the pH gradient to be monitored as focusing proceeded. beta-Lactamases extracted from antibiotic-resistant coliform organisms focused as sharp, straight bands upon visualization with nitrocefin. Results were known within two hours of applying the beta-lactamase extracts. The method allows a very economical use of expensive ampholyte and offers a quick and more simple alternative procedure for the identification of beta-lactamases than the conventional polyacrylamide gel method.