Pulldown

The Pull-down assay is designed to determine the interaction of two or more proteins. This method of purification and detection is different from the IP and Co-IP assays in that it is not an antibody to antigen interaction. A ″bait″ protein is tagged and captured on an immobilized ligand (support beads) by covalent attachment or through an affinity tag such as immobilized metal affinity chromatography (IMAC). This forms a complex, a ″secondary affinity support″, which is then incubated with a protein source such as cell or tissue lysate. The proteins of interest are eluted from the beaded support through a series of washes and collected by centrifugation. Similar to the IP and Co-IP assays, the sample is analyzed by SDS-PAGE, followed by Western blot detection.
The pull down assay is ideal for verification of co-immunoprecipitation results and an excellent method of identifying unknown protein to protein interactions along with the activation status of specific proteins.

Avidin Biotin Matrices

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A9207 Avidin−Agarose from egg white aqueous glycerol suspension
B0519 Biotin−Agarose PBS suspension
A1559 Monoclonal Anti-Biotin–Agarose antibody produced in mouse clone BN-34, purified immunoglobulin, PBS suspension
E5529 EZview Red Streptavidin Affinity Gel
S1638 Streptavidin−Agarose from Streptomyces avidinii buffered aqueous suspension

Glutathione S-transferase (GST)

Glutathione S-transferase (GST) is a 211 amino acid protein that can be found in most organisms. GST is often integrated into expression vectors of E. coli to produce fusion tags. The GST-Tag is a large protein tag, approximately 26 kDa and can be expressed in bacteria, yeast, mammalian, and infected insect cells. The GST-Tag is advantageous when protection of the recombinant protein from intracellular protease cleavage is required, and when there is a need to enhance the solubility of the tagged protein. In addition, the GST-Tag provides a high-affinity tag for easy purification and for pull-down experiments utilizing inexpensive affinity resins that are performed in mild elution conditions.

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E6406 EZview Red Glutathione Affinity Gel
G4510 Glutathione−Agarose lyophilized powder
G3907 Glutathione−Agarose set of 3 pre-packed columns (2.5 ml each)
G0924 Glutathione High Capacity Magnetic Agarose Beads

His

HIS-Select products from Sigma Life Science have the ability to purify histidine-tagged proteins quickly and with high selectivity. This is due to HIS-Select′s patented, non-charged, hydrophilic nickel chelate linkage. This non-charged linkage greatly diminishes non-specific binding.

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H8162 HIS-Select® Cobalt Affinity Gel
H0537 HIS-Select® HF Nickel Affinity Gel
P6611 HIS-Select® Nickel Affinity Gel
H9914 HIS-Select® Nickel Magnetic Agarose Beads