Advantages of separations on "giant" two-dimensional gels for detection of physiologically relevant changes in the expression of protein gene-products.

"Giant" 2-D gel electrophoretic protein separations (Methods Enzymol 91, part I, 190-214, 1983) offer a significant increase in resolving power over the usual methods. The increased capacity (good resolution up to 1 mg and as much as 10 mg of sample can be applied) and the improvement in resolution reveal some 3000 individual proteins when whole-cell extracts from diverse sources are separated on broad-range (pH 4.5-7.5) isoelectric-focusing (IEF) gels, and an additional 2000 when non-equilibrium and lower pH range IEF gels are also run. When applied to several types of steroid target cells, the giant-gel methods have allowed detection, among the minor protein species not resolved on standard-size gels, of a group of rapidly evolving (within the first 30 min or so) adrenal glucocorticoid inductions. These are likely mediators of the characteristic hormone effects. The giant gels have also greatly expanded the range of changes in protein gene-products in response to heat shock, growth factors, and retrovirus-induced malignant transformation, and should substantially enlarge the number of protein polymorphisms useful in genetic studies for linkage mapping.