4',5'-Dibromofluorescein (Eosinic acid) is a fluorescent dye utilized as a ligand in protein characterization through spectroscopic analysis.

Instructions:
a. Solution preparation: The dyeing solution contains 0.05~0.5% 4', 5'-Dibromofluorescein by weight volume, 20~100μM zinc chloride by molar concentration, 5~20% glycerol by volume of the solution, and 30%~70% methanol aqueous solution by volume of the solution; the preferred dyeing time is 8 min, the preferred 4', 5'-Dibromofluorescein concentration is 0.3%, the preferred zinc chloride concentration is 50μM, the preferred glycerol concentration is 10%, and the preferred carbonic acid and preferred methanol concentration is 40%.
b. Operation steps:
1. Place the protein sample after SDS-PAGE electrophoresis in the staining solution for 5~15min;
2. Discard the staining solution and add the developer solution for 1~5min, wherein the developer solution is a sodium acetate-acetic acid buffer solution with a molar concentration ratio of 100mM, pH=4.6, and the preferred development time is 2min;
3. After the gel is stained, it can be observed directly with the naked eye on a black background or under a scanner.