A Staining Method for Proteins and Dextrans on Cellulose Acetate

Abstract

AFTER the electrophoresis of human albumin labelled with iodine-131 in 0.06 M veronal buffer pH 8.6 on cellulose acetate, the strips were stained, dried, cleared in ‘Dekalin’ and scanned. The relationship between counting rate and dye uptake of amidoschwarz 10 B was linear up to, but not above, 30 µg/cm, 0.5 µl. of 6 per cent albumin applied evenly across 1 cm. Within this limit the method was suitable for the determination of albumin, in human serum as percentage total dye uptake times total protein by the biuret method. Thirty-three sera checked using an internal ¹³¹I-albumin standard gave results by this method and by the absolute albumin method of Lubran and Moss¹ which agreed within ± 0.2 g/100 ml. It was further observed that if the human eye could not see through the cleared band of stained albumin (or myeloma protein), then the strip was overloaded and in the non-linear range. No such simple safeguard existed for Ponceau S, where the relationship became non-linear above 15 µg/cm, and indeed previous scans using this dye had underestimated the albumin. Accordingly, the following staining method was adopted.