Spicy SDS-PAGE Gels: Curcumin/Turmeric as an Environment-Friendly Protein Stain

Abstract

Gel proteins are commonly stained with calorimetric/fluorescent dyes. Here, we demonstrate that heat-solubilized curcumin can serve as a nontoxic and environment-friendly fluorescent/colorimetric reversible protein stain. Curcumin, the yellow pigment found in the rhizomes of the perennial herb Curcuma longa (turmeric), is insoluble in aqueous solvents. However, heat (100 C) solubilization in water renders 1.5% of curcumin soluble. Curcumin solubilized by ethanol or alkali is ineffective in staining proteins. Heat solubilized curry spice turmeric stains proteins similarly. Staining is achieved in 30 min, with a sensitivity almost equaling that of Coomassie Brilliant Blue (CBB). Destaining is not required, and excess curcumin/turmeric can be discarded into the sink. Binding of proteins by silver inhibits curcumin binding, suggesting similarity of protein binding by silver and curcumin. It costs $1.5-2.0 to stain a mini-gel with curcumin, while turmeric costs less than 0.005 cent. CBB staining/destaining costs about 2 cents. However, CBB is toxic and its use necessitates specialized disposal efforts. Curcumin/turmeric, thus, can serve as an ideal nontoxic protein stain. © 2012 Springer Science+Business Media, LLC.