Nitrocellulose membranes ( BA85 ) were obtained from Schleicher and Schuell, Germany. GeneScreen and GeneScreen Plus membranes were from DuPont, USA. Millipore membranes ( 0.45 um ) were from Millipore Corporation, USA. 3 MM and 1 MM chromatography filter papers were from Whatman Ltd, U.K.