Ponceau S (Acid Red 112) is a common stain used for Western blot. Ponceau S may be used in an acidic aqueous solution that is compatible with antibody-antigen binding and stains proteins on the membrane red.

Physicochemical Properties

Molecular Formula	C22H12N4NA4O13S4
Molecular Weight	760.57
Exact Mass	759.887
CAS #	6226-79-5
PubChem CID	2723873
Appearance	Brown to black solid powder
Density	1.01 g/mL at 20 °C
Index of Refraction	n20/D 1.338
LogP	7.315
Hydrogen Bond Donor Count	1
Hydrogen Bond Acceptor Count	17
Rotatable Bond Count	4
Heavy Atom Count	47
Complexity	1430
Defined Atom Stereocenter Count	0
InChi Key	KQHKSGRIBYJYFX-UHFFFAOYSA-J
InChi Code	InChI=1S/C22H16N4O13S4.4Na/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);;;;/q;4*+1/p-4
Chemical Name	tetrasodium;3-hydroxy-4-[[2-sulfonato-4-[(4-sulfonatophenyl)diazenyl]phenyl]diazenyl]naphthalene-2,7-disulfonate
HS Tariff Code	2934.99.9001
Storage	Powder-20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.
Shipping Condition	Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Biological Activity

ln Vitro	Ponceau S, BS is a biochemical reagent that can be utilized in studies pertaining to life sciences as an organic compound or biological material.
References	[1]. Ponceau S waste: Ponceau S staining for total protein normalization. Anal Biochem. 2019 Jun 15; 575: 44-53. [2]. Litovchick. Staining the Blot for Total Protein with Ponceau S. Cold Spring Harb Protoc. 2020 Mar 2; 2020(3): 098459. [3]. Reversible Ponceau staining as a loading control alternative to actin in Western blots. Anal Biochem. 2010 Jun 15;401(2):318-20.
Additional Infomation	Ponceau S is an organic sodium salt that is the tetrasodium salt of 3-hydroxy-4-({2-sulfo-4-[(4-sulfophenyl)diazenyl]phenyl}diazenyl)naphthalene-2,7-disulfonic acid. It has a role as a histological dye and a fluorochrome. It is an organic sodium salt and an organosulfonate salt. It contains a Ponceau S(4-).

Solubility Data

Solubility (In Vitro)

DMSO: 100 mg/mL (131.48 mM) H2O: 35.71 mg/mL (46.95 mM)

Solubility (In Vivo)

Solubility in Formulation 1: ≥ 2.5 mg/mL (3.29 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution. For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly. Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.  (Please use freshly prepared in vivo formulations for optimal results.)

Preparing Stock Solutions		1 mg	5 mg	10 mg
	1 mM	1.3148 mL	6.5740 mL	13.1480 mL
	5 mM	0.2630 mL	1.3148 mL	2.6296 mL
	10 mM	0.1315 mL	0.6574 mL	1.3148 mL

*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.