Chromogenic β-Galactosidase Substrate for Blue-White Colony Screening
Catalogue No: ASE-906-1G
X-Gal is a chromogenic substrate for β-galactosidase, the standard tool for blue-white screening of recombinant clones in molecular biology laboratories. Upon cleavage by β-galactosidase, X-Gal releases galactose and 5-bromo-4-chloro-3-indoxyl, which spontaneously dimerises and oxidises to form an insoluble blue indigo dye — giving immediate, visual confirmation of enzyme activity.
- Blue-White Screening: Used with IPTG in lacZ α-complementation cloning vectors — blue colonies indicate an intact lacZ gene (non-recombinant), white colonies indicate successful insertional disruption (recombinant)
- Reporter Gene Assays: lacZ fusion constructs for gene expression studies, promoter analysis, and protein localisation
- General β-Galactosidase Research: lacZ pathway and enzyme activity studies
Blue-white screening requires a compatible lacZ-based host/vector system — confirm your strain and vector support α-complementation before use.
- Dissolve X-Gal in DMF or DMSO at 20–50 mg/mL (X-Gal is not water-soluble).
- Store stock at -20°C, protected from light.
- Use at 20–40 µg/mL final concentration in culture media/plates (commonly ~40 µL of stock per standard plate).
- If using an inducible system, add IPTG at 0.1–1.0 mM alongside X-Gal.
| Powder | -15 to -20°C, desiccated, protect from light and moisture |
| DMF/DMSO stock | -20°C, protected from light |
| Do not use if | Discolouration or contamination is observed |
| Product Name | X-Gal |
| Catalogue Number | ASE-906-1G |
| CAS Number | 7240-90-6 |
| Molecular Formula | C14H15BrClNO6 |
| Molecular Weight | 408.63 g/mol |
| Grade | Molecular Biology Grade |
| Manufacturer | AuSaMicS Pty Ltd, Melbourne, Australia |
| Appearance | White to pale yellow/off-white crystalline powder |
| Solubility | Insoluble in water; freely soluble in DMF or DMSO |
| Storage | -15 to -20°C, desiccated, protect from light and moisture |
Chromogenic substrate analogue of lactose; hydrolysed by β-galactosidase (lacZ gene product) to release an insoluble blue indigo dye. Used together with IPTG for visual blue-white screening of recombinant clones in lacZ α-complementation systems.
| Test | Organism / System | Expected Result | Acceptance Criterion |
|---|---|---|---|
| Functional cleavage | E. coli DH5α (lacZΔM15, pUC19), 37°C 16-18h on LB+Amp+IPTG+X-Gal | White colonies (recombinant) vs blue (control) | Clear blue/white differentiation in a compatible lacZ screening system |
- Sambrook, J. & Russell, D.W. (2001). Molecular Cloning: A Laboratory Manual, 3rd edn. CSHL Press.
- Horwitz, J.P. et al. (1964). Substrates for cytochemical demonstration of enzyme activity. J Med Chem. 7(4):574-575.
- Vieira, J. & Messing, J. (1982). The pUC plasmids. Gene. 19(3):259-268.
| Product Name | X-Gal |
| Catalogue Number | ASE-906-1G |
| CAS Number | 7240-90-6 |
| Intended Use | Laboratory reagent — molecular biology research use only |
| Supplier | AuSaMicS Pty Ltd | 36/25 Trafalgar Road, Epping VIC 3076 |
| ABN | 56 676 640 467 |
| Emergency Phone | +61 412 520 598 | Poisons Information Centre: 13 11 26 (Australia, 24 hr) |
| support@ausamics.com |
Hazard Statement: H302+H312+H332 – Harmful if swallowed, in contact with skin or if inhaled.
Precautionary Statements: P261 Avoid breathing dust/fume/gas/mist/vapours/spray. P280 Wear protective gloves/protective clothing/eye protection/face protection. P301+P312 IF SWALLOWED: call a POISON CENTER or doctor if you feel unwell. P302+P352 IF ON SKIN: wash with soap and water. P304+P340 IF INHALED: remove to fresh air and keep at rest. P305+P351+P338 IF IN EYES: rinse cautiously with water for several minutes.
Light-sensitive — protect from light during storage and use.
| Component | CAS No. | Concentration |
|---|---|---|
| X-Gal | 7240-90-6 | Single-constituent substance (see COA for lot-specific assay) |
| Inhalation | Remove to fresh air. Seek medical attention if breathing is difficult. |
| Skin Contact | Wash with plenty of soap and water. Seek medical advice if irritation persists. |
| Eye Contact | Rinse cautiously with water for several minutes. Remove contact lenses if present. |
| Ingestion | Rinse mouth. Do not induce vomiting. Call a poison centre or doctor if unwell. |
| Storage | -15 to -20°C, desiccated, protect from light and moisture |
| Handling | Handle in a well-ventilated area. Avoid generating or inhaling dust. Wash hands after handling. |
| Respiratory | Dust mask (P1/P2) if handling in poorly ventilated area |
| Eye protection | Safety glasses required |
| Gloves | Nitrile laboratory gloves |
Dispose of as laboratory chemical waste per local EPA regulations. Do not discharge to sewer in bulk quantity.
Not classified as Dangerous Goods for transport (ADG/IATA/IMDG) in the quantities and packaging typically supplied.
⬇ Download Full SDS — 16 Sections (PDF)This tab does not show a generic or "typical" result set, because a COA belongs to one manufactured lot — not to the product in general. To obtain the actual Certificate of Analysis for the container you have (or are about to order), contact us with the product code and lot number printed on the label.
| Product Code | ASE-906-1G |
| Lot Number | Printed on your container label |
| Test Parameter | Method |
|---|---|
| Appearance | Visual |
| Identity | TLC / HPLC |
| Purity | HPLC |
| Moisture | Karl Fischer / loss on drying |
| Functional performance | Blue-white screening test, E. coli DH5α + pUC19 |
This table lists what each lot is tested against — it is not a result. Your lot's actual measured values are stated on its own Certificate of Analysis.
| Released by | Hassan Salimi |
| Title | Founder and Technical Director |
| Organisation | AuSaMicS Pty Ltd |
Contact us with your order number, product code and lot number and we will issue the corresponding COA within 1 business day.
support@ausamics.com | +61 412 520 598
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