Thermo Scientific™

EZ-Link™ Phosphine-PEG4-Desthiobiotin, No-Weigh™ Format

Catalog number:  16133

 Related applications: Protein Labeling & Crosslinking

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Thermo Scientific EZ-Link Phosphine-PEG4-Desthiobiotin is a pegylated reagent whose biotin-like group is elutable from streptavidin, activated for chemoselective ligation and purification of azide targets tagged by metabolic labeling.

Features of EZ-Link Phosphine-PEG4-Desthiobiotin:

Desthiobiotin—analog of biotin allows easy elution from streptavidin, an ideal feature for affinity purification applications
Chemoselective—the phosphine reactive group is specific in biological samples for azide-tagged molecules, ensuring specific capture and purification of labeled targets
Compatible—Staudinger reaction chemistry proceeds efficiently in simple buffer conditions; requires no accessory reagents such as copper or reducing agents
PEG spacer—polyethylene glycol spacer arm helps maintain solubility of labeled molecules and decreases steric hindrance for affinity-binding to avidin, streptavidin or NeutrAvidin Protein
Soluble—easily dissolves in water-miscible solvents (e.g., DMSO) for subsequent dilution in aqueous reaction mixtures with cell lysates and other biological samples

When used in combination with azide labeling strategies, Phosphine-PEG4-Desthiobiotin enables affinity purification of protein interactions and post-translational modifications using streptavidin resins. The phosphine moiety selectively crosslinks via the Staudinger reaction mechanism to molecules that have been tagged or metabolically labeled with bioorthogonal azide groups. The desthiobiotin tag binds to streptavidin and other biotin-binding proteins with high specificity yet readily elutes with mild conditions (i.e., by competitive displacement with regular, free biotin). As such, this reagent is a useful alternative to Phosphine-PEG3-Biotin (Part No. 88901) for avidin-biotin techniques in which nondenaturing elution of the labeled proteins is desired. The No-Weigh Format (5 x 1 mg resealable vials) eliminates the difficulties associated with weighing small quantities of reagent and maximizes protection of unused reagent from degradation.

Desthiobiotin vs. Biotin
Desthiobiotin is a single-ring, sulfur-free analog of biotin that binds to streptavidin with nearly equal specificity but less affinity than biotin (1/Kd = 1011 vs. 1015M, respectively). Consequently, desthiobiotinylated bait proteins and their interacting partners can be eluted readily and specifically from streptavidin affinity resin using mild conditions based on competitive displacement with free biotin. For pull-down assay experiments with biological samples, this soft-release characteristic of desthiobiotin also helps to minimize co-purification of endogenous biotinylated molecules, which remain bound to streptavidin upon elution of the target protein complexes with free biotin. The modified avidin-biotin affinity system also eliminates the need to use harsh elution conditions that might disassociate complexes and/or damage the target protein or cell. Desthiobiotin-based techniques are ideal when using native or recombinant proteins that are not expressed with a fusion tag and when isolating captured proteins under native conditions, such as targeting intact cells or cell surface proteins.

Labeling with Phosphine Reagents
Azide groups can be introduced into proteins or other cellular targets through in vivo labeling with azide-derivatives of naturally occurring metabolic building blocks. Because phosphines and azides are foreign and invisible to biological systems (bioorthogonal), they comprise a chemoselective (mutually specific) ligation pair for labeling and conjugation.
For Research Use Only. Not for use in diagnostic procedures.


Cell Permeability: Cell-Impermeant
Spacer: Extra-Long, Pegylated
Chemical Reactivity: Azide
Label or Dye: Biotin Analog
Product Line: EZ-Link™
Product Size: 5 x 1 mg
Solubility: DMF (Dimethylformamide), DMSO (Dimethylsulfoxide), Water

Contents & storage

Store at 4°C.


Manuals & protocols

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