Overview
Bromo-galactoside reagent, commonly known as X-gal, is a chromogenic substrate widely used in molecular biology and biochemistry. It is specifically designed to detect the activity of the enzyme β-galactosidase, which cleaves the compound to produce a blue indigo dye. This property makes it indispensable in techniques like blue-white screening during cloning procedures, where it helps identify recombinant bacterial colonies. First synthesized in the mid-20th century, X-gal has become a staple in laboratories due to its reliability and ease of use. Its role in visualizing enzymatic activity has advanced research in gene regulation, protein expression, and cellular processes. The reagent's specificity for β-galactosidase ensures minimal interference in complex biological systems.
Physical and Chemical Properties
Bromo-galactoside reagent is a stable, crystalline powder with a molecular weight of 408.63 g/mol. It decomposes at temperatures around 200-210°C without a distinct boiling point. The compound is sparingly soluble in water but dissolves readily in organic solvents like DMF and DMSO, which are often used to prepare stock solutions for laboratory use. Its chromogenic reaction with β-galactosidase is highly sensitive, producing an intense blue color that is easily visible even at low enzyme concentrations. This reactivity is pH-dependent, with optimal performance in neutral to slightly alkaline conditions. The reagent’s stability under standard storage conditions (2-8°C) ensures a long shelf life when protected from light and moisture.
Main Applications
The primary application of bromo-galactoside reagent is in molecular biology for detecting β-galactosidase activity. In cloning experiments, it is used alongside IPTG (isopropyl β-D-1-thiogalactopyranoside) to screen for successful insertion of DNA into plasmid vectors. Colonies with intact β-galactosidase (lacZ gene) turn blue, while recombinant colonies remain white, streamlining the selection process. Beyond cloning, X-gal is employed in histochemistry and reporter gene assays to study gene expression patterns in tissues or cells. It is also used in diagnostic kits to identify bacterial strains expressing β-galactosidase. Its versatility and specificity make it a critical tool for researchers studying genetic regulation and enzyme kinetics.
Safety and Storage
While bromo-galactoside reagent is not classified as highly hazardous, standard laboratory precautions should be followed. Direct contact with skin or eyes may cause irritation, so gloves and safety goggles are recommended. Work should be conducted in a well-ventilated area or fume hood to avoid inhalation of powder. Proper storage is essential to maintain the reagent’s stability. It should be kept in a tightly sealed container at 2-8°C, protected from light and moisture. Exposure to high temperatures or humidity can degrade the compound, reducing its effectiveness in assays. Disposal should comply with local regulations for organic waste.
B2B Procurement Guide
When procuring bromo-galactoside reagent, prioritize suppliers with a track record of providing high-purity (≥98%) products suitable for sensitive assays. Bulk purchases may require advance notice due to the specialized nature of the chemical. Pricing varies based on quantity and purity, with research-grade material typically costing $50-$200 per gram. For large-scale or recurring orders, establish relationships with reputable manufacturers to ensure consistent quality. Verify certificates of analysis (CoA) for each batch to confirm purity and performance. Consider logistical factors like shipping conditions (e.g., cold chain for temperature-sensitive shipments) to prevent degradation during transit.
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