Ponceau S solution can be used for rapid staining of protein bands on PVDF and nitrocellulose membrane. Since the dye of this reagent is with negative charge, it can combine with amino-acid residue with positive charge. Meanwhile, it also can combine with non-polar area of protein to form red bands thereby. For the reversible protein staining, protein can be cleaned again by washing with distilled water, PBS buffer or other appropriate solution. With advantages of convenient use, low background and high sensitivity, this product can detect protein at minimum 250ng, but it is not suitable for protein detection on nylon membrane.