Ponceau S

Ponceau S

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Identifiers
CAS Number	6226-79-5
ChEBI	CHEBI:90319 Y
Jmol 3D model	Interactive image
InChI InChI=1S/C22H16N4O13S4/c27-22-20(43(37,38)39)10-12-9-16(41(31,32)33)6-7-17(12)21(22)26-25-18-8-3-14(11-19(18)42(34,35)36)24-23-13-1-4-15(5-2-13)40(28,29)30/h1-11,27H,(H,28,29,30)(H,31,32,33)(H,34,35,36)(H,37,38,39)/b24-23+,26-25+
SMILES OC1=C(N=NC3=CC=C(N=NC4=CC=C(S(=O)(O)=O)C=C4)C=C3S(=O)(O)=O)C2=C(C=C(S(=O)(O)=O)C=C2)C=C1S(=O)(O)=O
Properties
Chemical formula	C22H16N4O13S4
Molar mass	672.63 g·mol−1
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Ponceau S, Acid Red 112, or C.I. 27195 is a sodium salt of a diazo dye of a light red color, that may be used to prepare a stain for rapid reversible detection of protein bands on nitrocellulose or polyvinylidene fluoride (PVDF) membranes (Western blotting), as well as on cellulose acetate membranes. A Ponceau S stain is useful because it does not appear to have a deleterious effect on the sequencing of blotted polypeptides and is therefore one method of choice for locating polypeptides on Western blots for blot-sequencing. It is also easily reversed with water washes, facilitating subsequent immunological detection. The stain can be completely removed from the protein bands by continued washing. Common stain formulations include 0.1% (w/v) Ponceau S in 5% acetic acid or 2% (w/v) Ponceau S in 30% trichloroacetic acid and 30% sulfosalicylic acid.

A nitrocellulose membrane stained with Ponceau S dye for protein detection during western blotting. The blue bands on the left are protein markers for various molecular weights.

See also

• Western blotting
• Coomassie Brilliant Blue
• Ponceau family of Azo dyes