Europium–Streptavidin Conjugates

Our Europium (Eu) Streptavidin Conjugates are manufactured using covalent attachment of streptavidin to the specially treated surface of 200nm Eu particles. The surface treatment of the particles makes the conjugates resistant to aggregation, while the extremely broad Stokes shift of the Eu chelate particle allows for higher sensitivity in any immunoassay, preventing nonspecific fluorescence interference.

Streptavidin is a tetrameric biotin binding protein that is isolated from Streptomyces avidinii. It is composed of identical subunits, with the tetramer having a molecular weight of approximately 53kDa. Each subunit binds one biotin molecule with a very high degree of specificity and affinity. The streptavidin–biotin complex is the strongest known noncovalent interaction (Kd = 10-15M) between a protein and a ligand.

The combination between the Eu fluorescence properties and the specific interaction of streptavidin with biotin makes our conjugate a useful tool in designing detection systems with excellent sensitivity.

Features and Benefits of Europium–Streptavidin Conjugates

  • Highly stable, easy to use conjugates
  • Resistant to aggregation
  • No sonication, shaking or vortexing required
  • No need for blocking solution
  • Possibility to work with low conjugate concentrations
  • Conjugates can be run on an immunochromatographic assay as well as a microwell based assay*
  • Lyophilized for easy shipping and long term storage.


Material: Polystyrene

Appearance: White

Dye: Europium chelate

Specificity: Biotin

Excitation: 365nm

Emission: 610nm

Format: Lyophilized

Product size: 1 Mini and 1 Midi vial

Storage: -20oC.

Please get in contact with us to know more about this product.

Expedeon Competitor data Eu–Streptavidin Conjugates

Figure 1. Brighter than the competitor product under UV excitation.

Figure 2. Typical ELISA data with a time resolved fluorescence (TRF) readout. Varying dilutions of Expedeon’s Europium–Streptavidin conjugate were added to a plate coated with biotinylated ovalbumin, and detected using a plate reader.

When excited with UV light, the Eu chelate particle shows a maximal absorbance at 365nm and emits at 610nm. The large Stokes shift leads to a low background signal and makes the conjugated particles ideal for immunochromatographic assay as well as a microwell based assay.
Thanks to the extended lifetime of approximately 0.5 milliseconds, the 200nm Eu Streptavidin conjugate can be used in a wide range of time resolved fluorescence application for the indirect detection of antigens and DNA targets in many biotin / streptavidin interaction based assays.


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