The fluorescent, noncovalent staining method, using SYPRO® Ruby dye resembles colorimetric staining procedures, such as colloidal Coomassie Blue dye staining. The dye provides noncovalent staining and is applied postelectrophoretically, which means that no alteration in the migration of proteins during electrophoresis can occur. The SYPRO Ruby dye-based staining method is also compatible with downstream applications such as Edman-based protein sequencing and peptide mass profiling by mass spectrometry-based methods.