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Biotin is commonly used as a protein tag to facilitate the detection, purification, and immobilization of the proteins. The bond between biotin and its binding partner Avidin (or Streptavidin) is unique in the following ways:
- Strong (Ka of 1015 M-1)
- Minimal interference
- Biotin-avidin binding structure
With characteristics mentioned above, biotin-(strept) avidin system is now considered a versatile independent technology in following applications.
ELISA - Biotinylated proteins can be used in ELISA as two-way antibodies for both capture and detection with high specificity and detection sensitivity.
FACS - Biotinylated proteins can be used along fluorophore-tagged SA to detect/isolate cells expressing particular surface markers.
Biopanning - It’s a technique often used for the selection of phage displays during antibody drug development. Biotinylated proteins can be used with SA-coated magnetic beads/surface in biopanning with higher coating density and uniformed antigen presentation.
SPR - It’s a standard method used by pharmaceutical researchers to study protein binding kinetics. Biotinylated proteins can be used along with Biacore Sensor Chip SA for SPR analysis with low baseline drift and noise, and low activity loss during surface regeneration cycle.
Immuno-Capture and Enrichment - This approach is used to isolate low abundant antibody drug in high complicated plasma sample, in order to monitor drug concentration in clinical or translational research. Biotinylated proteins can be used to isolate antibodies from plasma or other biological fluid for subsequent analyses with high sensitivity, and the processed sample can be easily analyzed in quantitative mass spectrometry.
Mabsol[R] biotinylated protein collection includes two unique and complimentary product series, the PrecisionAvi series built upon the Avitag[TM] technology, and the UltraLys series produced using the in-house developed chemical labeling method. These products are made with every attention to details. The products in this series are exclusively produced using the AvitagTM technology. Briefly, a unique 15 amino acid peptide, the Avi tag, is introduced into the recombinant protein during expression vector construction. The single lysine residue in the Avi tag is enzymatically biotinylated by the E. Coli biotin ligase BirA.
This single-point enzymatic labelling technique brings many advantages for commonly used binding assays. The biotinylation happens on the lysine residue of Avi tag, and therefore does NOT interfere with the target protein’s natural binding activities. In addition, when immobilized on an avidin-coated surface, the protein orientation is uniform because the position of the Avi tag in the protein is precisely controlled since biotin is labelled at single lysine in the Avi tag. The labelling ratio range is 0.5-1.
UltraLys Series is a unique series of chemically labelled biotinylated proteins with ultra-sensitivity. The products in this series are produced using our in-house developed chemical labelling approach. The primary amines in the side chains of lysine residues and the N-terminus of protein are conjugated with biotins.
Chemical labelling usually results in multiple biotin attachment on a single protein molecule, which could potentially lead to higher detection sensitivity.
The labelling ratio is depended on the number of accessible lysine residues in the protein, and usually more than 1.
For further details and examples please click here.