Quantitative analysis of electrophoretically separated proteins using Coomassie blue.

Electrophoresis of 125I-labelled rat albumin from 0.5 to 700 ng was performed with a 5 microliter capillary tube in which 4-40% continuous gradient polyacrylamide gel was prepared. The linear relationship was obtained by using double logarithm plots between protein amounts and densitometric areas of the protein bands stained with Coomassie blue. The radioactivities of the same gels and the protein amounts were also shown to be linear. In the case of rat gamma-globulin, the linear relationship was also obtained. As an applied example of this method, the urinary gamma-globulin excretion showed marked changes caused by the circadian rhythm in rats.