3,3'-Diaminobenzidine

3,3'-Diaminobenzidine
IUPAC name 3,3',4,4'-Tetraamino-diphenyl
Identifiers
CAS number	91-95-2,  [7411-49-6] (4HCl)
ChemSpider	6804 Y
RTECS number	DV8750000 DV8753000 (4HCl)
Jmol-3D images	Image 1
SMILES c2(c1cc(N)c(N)cc1)ccc(N)c(N)c2
InChI InChI=1S/C12H14N4/c13-9-3-1-7(5-11(9)15)8-2-4-10(14)12(16)6-8/h1-6H,13-16H2 Y Key: HSTOKWSFWGCZMH-UHFFFAOYSA-N Y InChI=1/C12H14N4/c13-9-3-1-7(5-11(9)15)8-2-4-10(14)12(16)6-8/h1-6H,13-16H2 Key: HSTOKWSFWGCZMH-UHFFFAOYAU
Properties
Molecular formula	C12H14N4 C12H18Cl4N4 (4HCl)
Molar mass	214.27 g/mol 360.11 g/mol (4HCl)
Melting point	175–177 °C 280 °C (4HCl.2H2O)
Hazards
MSDS	External MSDS
EU classification	Harmful (Xn)
S-phrases	S36 S37 S45
R/S statement	R20 R21 R22 R40
NFPA 704	1 2 2
LD50	mouse, oral Acute: 1834 mg/kg.
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

3,3'-Diaminobenzidine (DAB) is an organic compound. This derivative of benzidine is a precursor to polybenzimidazole fiber^[1]. As its water-soluble tetrahydrochloride, it has been used in immunohistochemical staining of nucleic acids and proteins.^{[citation needed]}

Preparation

Diaminobenzidine, which is commercially available, is prepared by reacting 3,3'-dichlorobenzidine and ammonia with a copper catalyst at high temperature and pressure, followed by acidic workup.^[2]

Applications

Diaminobenzidine is oxidized by hydrogen peroxide in the presence of hemoglobin to give a dark-brown color. This is used to detect fingerprints in blood.^[3] Improperly prepared tissue samples may give false positives^[4] In research, this reaction is used to stain cells that were prepared with hydrogen peroxidase enzyme, following common immunocytochemistry protocols. In research being done on Alzheimer's Disease, Aβ protein amyloid plaques are targeted by a primary antibody, and subsequently by a secondary antibody, which is conjugated with a peroxidase enzyme. This will bind DAB as a substrate and oxidize it, producing an easily observable brown color. Plaques can then be quantified for further evaluation.^[5] One other method uses complexes of injected biocytin with avidin or streptavidin, biotin, and then peroxidase.

References

1. ^ Hans Schwenecke, Dieter Mayer “Benzidine and Benzidine Derivatives” in Ullmann’s Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim.
2. ^ US 3943175, Druin, Melvin L. & Oringer, Kenneth, "Synthesis of pure 3,3'-diaminobenzidine", issued 1976-03-09, assigned to Celanese Corporation 
3. ^ "D.A.B. (Diaminobenzidine)". Chesapeake Bay Division, International Association for Identification. http://www.cbdiai.org/Reagents/dab.html. Retrieved 2007-11-09. 
4. ^ "Liquid DAB Substrate" (pdf). Dako. http://www.dako.co.uk/prod_downloadpackageinsert.pdf?objectid=105426004. Retrieved 2008-02-02. 
5. ^ Falangola, M. F., Lee, S. P., Nixon, R. A., Duff, K., & Helpern, J.K. (2005). Histological co-localization of iron in Abeta plaques of PS/APP transgenic mice. Neurochemical Research, 30(2). 201-205.

External links

• Fishersci.com
• Polysciences.com