2-Nitrophenyl-beta-D-galactopyranoside Chemical Properties

Melting point:

186-193 °C (dec.)

alpha 

-70 º (c=1, H2O)

Boiling point:

442.39°C (rough estimate)

Density 

1.3709 (rough estimate)

refractive index 

-68.8 ° (C=1, H2O)

storage temp. 

2-8°C

solubility 

DMSO (Slightly), Water (Slightly, Heated, Sonicated)

pka

12.69±0.70(Predicted)

form 

Powder

color 

White to very slightly yellow

optical activity

[α]20/D 70±1°, c = 1% in H2O

Water Solubility 

Soluble in water.

BRN 

92207

InChIKey

KUWPCJHYPSUOFW-RMPHRYRLSA-N

CAS DataBase Reference

369-07-3(CAS DataBase Reference)

NIST Chemistry Reference

Galactopyranoside, o-nitrophenyl, beta-d-(369-07-3)

Safety Information

Hazard Codes 

Xi

Risk Statements 

36/37/38

Safety Statements 

22-24/25-36-26

WGK Germany 

3

F 

3-10-21

HS Code 

29400090

MSDS

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2-Nitrophenyl-beta-D-galactopyranoside Usage And Synthesis

Description

2-Nitrophenyl-β-D-galactopyranoside (ONPG) is a colorimetric and spectrophotometric substrate for detecting β-galactosidase activity. This compound is usually 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 utilizing a colorimetric assay (at 420 nm wavelength). β-Galactosidase is required for lactose utilization, so the intensity of the color produced can be used to measure the enzymatic rate. Though ONPG mimics lactose and is hydrolyzed by β-galactosidase, it cannot 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.

Chemical Properties

White Crystalline Solid

Uses

2-Nitrophenyl-beta-D-galactopyranoside is a β-Galactosidase substrate for colorimetric and EIA applications; counterpart of widely employed pNPP/alkaline phosphatase substrate.

Definition

ChEBI: A beta-D-galactoside having a 2-nitrophenyl substituent at the anomeric position.

General Description

ONPG (2-Nitrophenyl β-D-galactopyranoside) is a colorimetric substrate for β-galactosidase.

Biochem/physiol Actions

β-galactosidase, breaks down lactose into galactose and glucose. β-Galactosidase is not lactose specific and can act on simple galactosides. 2-Nitrophenyl β-D-galactopyranoside hydrolysis results in the release of galactose and a yellow chromogenic compound. The test substrate does not depend on an induced or constitutive permease enzyme to enter the cell, therefore reactions are rapid and occur within a 24-hour period.

Purification Methods

Purify 2-nitrophenyl--D-galactopyranoside by recrystallisation from EtOH. [Seidman & Link J Am Chem Soc 72 4324 1950, Snyder & Link J Am Chem Soc 75 1758 1953]. It is a chromogenic substrate for -galactosidases [Jagota et al. J Food Sci 46 161 1981]. [Beilstein 17/7 V 52.]

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