Sirius Red F 3B (Direct Red 80) is an azo dye primarily used in staining methods for collagen and amyloid.^[1] It has the molecular formula C₄₅H₂₆N₁₀Na₆O₂₁S₆.

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Sirius Red

Names
IUPAC name Hexasodium (3E)-4-oxo-7-[[(6E)-5-oxo-7-sulfonato-6-[[2-sulfonato-4-[(4-sulfonatophenyl)diazenyl]phenyl]hydrazinylidene]naphthalen-2-yl]carbamoylamino]-3-[[2-sulfonato-4-[(4-sulfonatophenyl)diazenyl]phenyl]hydrazinylidene]naphthalene-2-sulfonate
Other names Direct Red 80; Picrosirius Red
Identifiers
CAS Number	2610-10-8 Y
3D model (JSmol)	Interactive image
ECHA InfoCard	100.018.208
PubChem CID	9571131
UNII	1294D5G72N Y
CompTox Dashboard (EPA)	DTXSID8044628
SMILES C1=CC(=CC=C1N=NC2=CC(=C(C=C2)N/N=C/3\C(=O)C4=C(C=C3S(=O)(=O)[O-])C=C(C=C4)NC(=O)NC5=CC6=C(C(=O)/C(=N\NC7=C(C=C(C=C7)N=NC8=CC=C(C=C8)S(=O)(=O)[O-])S(=O)(=O)[O-])/C(=C6)S(=O)(=O)[O-])C=C5)S(=O)(=O)[O-])S(=O)(=O)[O-].[Na+].[Na+].[Na+].[Na+].[Na+].[Na+]
Properties
Chemical formula	C45H26N10Na6O21S6
Molar mass	1373.05 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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In histology, sirius red staining is used in various domains of diagnostic to observe fibrosis levels in a lot of cases of inflammation induced by cancer, vascular or metabolic pathologies.^[2]

In bright field microscopy the following can be observed:

• The nuclei in yellow
• The cytoplasm in yellow
• Collagen fibers in red
• Muscular fibers in yellow
• Red blood cells in yellow

• Collagen Hybridizing Peptide, a peptide that stains denatured collagen in tissues