B3928

Blue-White Select^™ Screening Reagent

for selection of recombinant bacterial clones

• Synonym(s): Blue-White Reagent, Screening Reagent, Selection Reagent
• UNSPSC Code: 12352200
• NACRES: NA.85

Properties

• grade: for molecular biology
• Quality Level: 200
• form: liquid
• usage: sufficient for 125 dishes (90 mm)
• technique(s): nucleic acid detection: suitable
• suitability: suitable for nucleic acid staining
• shipped in: dry ice
• storage temp.: −20°C

Description

General description

Sigma′s Blue-White Select^™ Screening Reagent is a chromogenic substrate for β-galactosidase, used to determine the presence or absence of a cloned DNA insert in bacteria growing on agar plates. Blue-White Select^™ Screening Reagent is designed for blue-white selection of recombinant bacterial colonies with the lac+ phenotype.

Features and Benefits

• Intense color contrast for easy colony selection
• Convenient, ready-to-use solution

Components

40 mg/mL IPTG
40 mg/mL X-Gal
(prepared in DMSO)

Principle

When Blue-White Select^™ Screening Reagent is cleaved by β-galactosidase, the resulting product will form a blue precipitate. Lac+ colonies grown in the presence of Blue-White Select^™ Screening Reagent remain white in color, allowing for easy differentiation between lac+ and lac- colonies.

The technique is based on vectors such as the pUC and the M13mp series that carry a fragment of the β-galactosidase gene encoding an a-fragment of β-galactosidase. Exploitation of these vectors requires use of a bacteria strain carrying the complementing gene fragment to allow the assembly of an active complex, resulting in the formation of blue colonies. Disruption of the ß-galactosidase gene by insertion of a DNA fragment into the vector′s multiple cloning site results in the loss of functional β-galactosidase activity; these colonies remain white, allowing for easy differentiation between lac+ and lac- colonies.

Legal Information

Blue-White Select is a trademark of Sigma-Aldrich Co. LLC

Safety Information

• Storage Class: 10 - Combustible liquids
• wgk_germany: WGK 3
• flash_point_f: 188.6 °F
• flash_point_c: 87 °C
• ppe: Eyeshields, Gloves, type ABEK (EN14387) respirator filter