Computer-AssistedAnalysisof Two-DimensionalElectrophoresesof

Two-dimensional electrophoresis in polyacrylamide gel provides a highly reproducible display of biosynthetically pulse-labeled cellular polypeptides, whose relative rates of synthesis can be judged from the relative spot densities they produce in fluorographic images of the electrophor-eses. When experimental and control cell populations synthesize protein at differing rates, either the sample load per gel or the duration of exposure of gel to film may be adjusted to produce comparable experimental and control images with no alteration in the rank order of relative spot density. However, variation in the duration of pulse-labeling may significantly alter relative spot density. Film density saturation and nonlinear response to radiation may also alter relative spot density for polypeptides with very large or very small amounts of radioactivity. Stimulation o