QualityControlin Assayof High- DensityLipoproteinCholesterol

CLINICAL CHEMISTRY. Vol. 26, No. 1, 1980 177 may then be used to make the precipitin lines visible. The stain that seemed to give the best contrast between precipitin lines and membrane background was Procion Brilliant Blue M-RS (Inolex Corp., Glenwood, IL). An aqueous stain stock solution, 1.2 g/L was prepared and membranes placed in a working mixture of stain stock/water/acetic acid/methanol (2/2/2/1) for 10 mm. Excess stain was then removed by two 10-mm rinses in acetic acid/methanol/water (1/3/5). Both Ponceau S and Coomassie Brilliant Blue R were also tried. The first gave too light a contrast; the second did not rinse well from the membrane #{149} background. After the membrane was dried in warm air for 5 mm, the heights of the precipitin peaks could be measured. EIA peak heights were reproducible to within ±4.3% across a membrane and within ±5.0% between membranes. I thank Dr. Stephen Kimzey and Mrs. Carol Keskitalo, Medical Sciences Division, Johnson Space Center, Houston, TX, in whose laboratory this work was done during my tenure as NASA/ASEE Summer (1979) Faculty Fellow; and Dr. J. Paul Miller, Baylor College of Medicine, for his gift of pure ApoA-I and its monospecific antisera, prepared in goat.