[A new method for the preparation of linear polyacrylamide gradients (author's transl)]

Continuous linear gradients improve electrophoretic separations in polyacrylamide. They are obtained by overlayering equal volumes of two monomer solutions with different acrylamide concentrations, namely 180-260 and 23-50 g/l, in the usual gel tubes. The tubes are tilted 3-10 degrees to the horizontal, and rotated around their longitudinal axis until the parts of both solutions in contact are mixed homogeneously. Subsequent polymerization takes place in the vertical position. The more concentrated lower solution contains 4-nitrophenol, so that the final polymer concentration at any point of the gel can be measured densitometrically. The construction and handling of the rotation device are simple and yield highly reproducible results. This versatile method was evaluated for the separation of proteins, lipoproteins, and enzymes in human serum and yields 27-30 protein fractions by additional use of a pH-gradient.