Biacore affinity determination

In essence, this technique allows for the detection of surface binding interactions in real time without the use of labels. Immunosensors that rely on these principles are commercially available from Biacore AB (formerly Pharmacia Biosensor). These are based on the popular BIACORE 3000, BIACORE 2000 and BIACORE probe instruments in conjunction with disposable sensor chips, which may be purchased with affinity capture chemistries in place (e.g. SA5 Sensor Chips with streptavidin bearing surfaces for capture of biotinylated compounds) [92]. These devices incorporate micro-fluidic systems for delivery of reagents required for analysis and are capable of measuring affinities and kinetics of antibody-antigen interactions in addition to analyte concentrations, which can be determined to the picomolar range [93]. 

As shown above, a broad optimization effort for the 9-position had led to the identification of p-chlorobenzamide as the best substituent ( 147, entry 63 in Table 7). Because the sheer enlargement of the hydrophobic group in the 2-position did not exhibit improved affinities (entries 6-12 in Table 7), the electron densities of the aromatic aglycones were altered in a next step (entries 4-9, Table 8) [81]. Then, with the substituents in the 2- and 9-positions set, a further optimization of the acyl group in the 5-position was conducted (entries 10-16). The binding properties of the neuraminic acid derivatives 155-167 again were evaluated with the hapten binding assay relative to sialoside 147. In addition, the dissociation constants Kjj were determined in a surface plasmon resmiance (SPR) based biosensor (Biacore) experiment [70]. 

Nieba L., Krebber A. and Pliickthun A. (1996) Competition BIAcore for measuring true affinities Large differences from values determined from binding kinetics. Anal. Biochem. 234 155-165. 

---