X-Gal (CAS 7240-90-6) | β-Galactosidase Substrate for Blue-White Screening

X-Gal (CAS 7240-90-6)

5-Bromo-4-chloro-3-indolyl β-D-galactopyranoside

Chromogenic Substrate for β-Galactosidase Detection

Catalog Number: ASE-906
HS / AHECC Code: 2932.99.00 – Heterocyclic compounds (laboratory reagents)
Grade: Molecular Biology / Research
Form: Powder

Synonyms

• BCIG

• 5-Bromo-4-chloro-3-indolyl β-D-galactopyranoside

• 5-Bromo-4-chloro-3-indolyl β-D-galactoside

• X-Gal

Technical Specifications

• CAS Number: 7240-90-6

• Molecular Formula: C₁₄H₁₅BrClNO₆

• Molecular Weight: 408.64 g/mol

• Appearance: Off-white to pale powder

• Light Sensitivity: Light-sensitive compound

Product Overview

X-Gal is a highly specific chromogenic substrate used for the detection of β-galactosidase (lacZ) activity in molecular biology, microbiology, and biochemical applications.

In its intact form, X-Gal is colourless. Upon enzymatic hydrolysis by β-galactosidase, it releases 5-bromo-4-chloro-3-hydroxyindole, which rapidly oxidises and dimerises to produce an insoluble blue indigo precipitate.

This visible blue reaction enables rapid identification of lacZ-positive colonies and enzyme activity in a wide range of experimental systems.

Core Applications

• Blue-white screening of recombinant Escherichia coli colonies

• Detection of β-galactosidase activity in cloning workflows

• Reporter gene assays using the lacZ system

• Indicator substrate in coliform and E. coli detection media

• Enzymatic detection in biochemical and blotting assays

Principle of Reaction

X-Gal is hydrolysed by β-galactosidase, cleaving the galactoside bond and forming an indoxyl intermediate.
This intermediate oxidises and dimerises to produce an insoluble blue compound at the site of enzyme activity.

In cloning systems, X-Gal is commonly used with IPTG, which induces lacZ expression by inactivating the lac repressor. This combination enables clear differentiation between:

• lacZ-positive colonies → Blue

• lacZ-negative (recombinant) colonies → White

Key Features & Benefits

• Highly specific substrate for β-galactosidase

• Produces intense, clearly visible blue precipitate

• Essential reagent for blue-white screening workflows

• Compatible with IPTG-inducible lac systems

• Reliable performance in molecular cloning applications

Storage & Stability

• Store at 2–8 °C

• Protect from light and moisture

• Keep container tightly sealed

• Prepare solutions fresh or store aliquots appropriately

Quality & Compliance

• Supplied for molecular biology and biochemical research

• Manufactured under controlled handling conditions

• Certificate of Analysis (COA) available

• Safety Data Sheet (SDS) available

Intended Use Statement

For laboratory research use only.
Not for human or veterinary therapeutic use.