Information Protein spots stained with ChromaPhor Green Stain are much more sensitively detected and quantified by helium-neon laser scanners than are spots stained with Coomassie blue. This offers significant advantages for analysis of 2-D gel patterns. One ancillary service often used is quantification of proteins resolved on 2-D gels. For example, when evaluating 2-D gel results, a researcher may notice that a few polypeptides in a cell culture preparation appear to be increased in concentration by hormone treatment. To convert the visual scoring of spot densities to quantitative data, the stained 2-D gels are scanned by a laser densitometer and the resultant images are analyzed using a microcomputer.
Integrated densities are determined for the spots of interest and for control spots.
Once averages and standard deviations are obtained, statistics are used to determine the significance of the observation. A decision then may be made to proceed with partial sequencing and cloning to further characterize the spots of interest. In cases where radiolabeling is not convenient or desirable, Coomassie blue staining often is used for 2-D quantification. One problem with Coomassie blue, however, is low sensitivity. Figure 1 shows the absorbance spectra of the two stains.