Comparison of the polypeptide composition of cystic fibrosis plasma with normal plasma by high resolution electrophoresis

Abstract

Cystic fibrosis and normal plasma proteins were compared by the method of high resolution two-dimensional electrophoresis in polyacrylamide gels. For the first dimension, samples were treated with urea and dithiothreitol and then subjected to isoelectric focusing in pH gradients of 3.5–10.0 or 5.0–8.0. The second dimension involved sodium dodecyl sulfate electrophoresis into gels of 10–20% polyacrylamide gradients. In one “blind” experiment, an attempt to segregate 12 plasma samples into six cystic fibrosis and six normals based on the polypeptide patterns was unsuccessful. Experiments using known cystic fibrotic and normal plasma samples (three further samples of each), depleted of albumin prior to electrophoresis, also failed to confirm the presence of cystic fibrosis related proteins or peptides. We have not been able to substantiate, by electrophoretic means, changes of sialic acid content of any plasma glycoprotein which might be expected to occur, for example, as a result of the postulated altered sialyltransferase activity in cystic fibrosis liver.