Ortho-Nitrophenyl-β-galactoside

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ortho-Nitrophenyl-β-galactoside

IUPAC name (2R,3R,4S,5R)-2-(Hydroxymethyl)-6-(2-nitrophenoxy)oxane-3,4,5-triol
Other names 2-Nitrophenylgalactoside
Identifiers
CAS number	369-07-3
PubChem	123646
	MeSH	2-nitrophenylgalactoside
Jmol-3D images	{{#if:O=[N+]([O-])C1=CC=CC=C1O[C@@H]2O[C@H](CO)[C@H](O)[C@H](O)[C@H]2O\|Image 1
SMILES O=[N+]([O-])C1=CC=CC=C1O[C@@H]2O[C@H](CO)[C@H](O)[C@H](O)[C@H]2O
Properties
Molecular formula	C₁₂H₁₅NO₈
Molar mass	301.25 g mol⁻¹
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

ortho-Nitrophenyl-β-galactoside (ONPG) is a colorimetric and spectrophotometric substrate for detection of β-galactosidase activity. This compound is normally colorless. However, if β-galactosidase is present, it hydrolyzes the ONPG molecule into galactose and ortho-nitrophenol. The latter compound has a yellow color that can be used to check for enzyme activity by means of a colorimetric assay (at 420 nm wavelength). β-Galactosidase is required for lactose utilization, so the intensity of the color produced can be used as a measure of the enzymatic rate.

Though ONPG mimics lactose and is hydrolyzed by β-galactosidase, it is unable to act as an inducer for the lac operon. Without another lactose analog that can act as an inducer, such as isopropyl β-D-1-thiogalactopyranoside (IPTG), β-galactosidase will not be transcribed and ONPG will not be hydrolyzed.

v t e Glycosides

Bond	O-glycosidic bond N-glycosidic bond S-glycosidic bond C-glycosidic bond

Geometry	α-Glycoside β-Glycoside 1,4-Glycoside 1,6-Glycoside

Glycone	Fructoside Galactoside Glucoside Glucuronide Rhamnoside Riboside

Aglycone	Alcoholic glycoside Anthraquinone glycoside Cardiac glycoside Bufadienolide Cardenolide Coumarin glycoside Cyanogenic glycoside Flavonoid glycoside Glycosylamine Phenolic glycoside Saponin Steviol glycoside Thioglycoside

Biochemical families: carbohydrates alcohols glycoproteins glycosides lipids eicosanoids fatty acids / intermediates phospholipids sphingolipids steroids nucleic acids constituents / intermediates proteins Amino acids / intermediates tetrapyrroles / intermediates

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