Bio-Rad negative stains are based on selective precipitation of metal ions in gels, leaving protein bands unstained and unmodified. Since the protein is unmodified, it is fully compatible with downstream applications such as mass spectrometry. These are easy and rapid procedures, requiring less than 15 minutes to complete. Bio-Rad offers two types of negative stains for polyacrylamide gel staining, both of which offer higher sensitivity than Coomassie Brilliant Blue R–250 stain.
Zinc stain – Bio-Rad zinc stain and destain kit, derived from the method of Fernandez-Patron et al. (1992), is a reversible negative stain for SDS- PAGE gels. A simple three-step staining procedure allows visualization of negatively stained bands in approximately 15 minutes. The opaque white background of the gel creates a high contrast for visualizing the clear bands when viewed against a dark background. Gels can be completely destained in 15 minutes, allowing western blotting, amino acid analysis, or N-terminal sequencing to be performed on samples.
Copper stain – Bio-Rad copper stain and destain kit, derived from the method of Lee et al. (1987), allows visualization of protein bands on SDS-PAGE gels in just 10 minutes. Because the proteins are negatively stained, no destaining step is necessary to see the bands. Proteins are reversibly fixed in the gel, allowing elution or blotting after a 15 minute destaining step. Copper stain has greater sensitivity than Coomassie Brilliant Blue R–250 stain.
Fernandez-Patron C et al. (1992). Reverse staining of sodium dodecyl sulfate polyacrylamide gels by imidazole-zinc salts: sensitive detection of unmodified proteins. Biotechniques 12, 564–573.
Lee C et al. (1987). Copper staining: a five-minute protein stain for sodium dodecyl sulfate-polyacrylamide gels. Anal Biochem 166, 308–312.