Ponceau S

Ponceau S is a light red stain commonly used to stain proteins on membranes used in Western blotting, such as nitrocellulose and polyvinylidene fluoride (PVDF). As an anionic diazo dye, Ponceau S binds electrostatically to the positively charged regions of proteins. This binding is reversible, and the stain can easily be washed away with water, even to the point of complete destaining. This quality of Ponceau S allows further downstream work in addition to the Western blot, such as other immunoblots and blot-sequencing.