| ortho-Nitrophenyl-β-galactoside | |
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(2R,3R,4S,5R)-2-(Hydroxymethyl)-6-(2-nitrophenoxy)oxane-3,4,5-triol |
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Other names
2-Nitrophenylgalactoside |
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| Identifiers | |
| CAS number | 19710-96-4 |
| PubChem | 123646 |
| MeSH | 2-nitrophenylgalactoside |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C12H15NO8 |
| Molar mass | 301.249 |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) | |
| Infobox references | |
ortho-Nitrophenyl-β-galactoside (ONPG) is a colorimetric and spectrophotometric substrate for detection of beta-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 IPTG, β-galactosidase will not be transcribed and ONPG will not be hydrolyzed.
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