Antibody molecules often show a range of mechanisms (monoclonal, polyclonal, avidty effcts) and wildly varying dissociation equilibrium constants (KD), or simply affinity), which can be elucidated with the SKi Pro biomolecular interaction analysis approach. By removing the need to use labels, the real time kinetics of the antibody-antigen interaction may be followed and quantified.
In the antibody binding figure a polyclonal anti-IgG is shown interacting with human IgG. A close look at the two-state fit (orange lines), as it differs from the label free signal (gray lines) shows the heterogeneity one would expect for a polyclonal antibody. Here, human IgG is interacted at concentrations between 160 pM and 40 nM.
In the case of the mouse monoclonal antibody interacting with leptin, the two state fit appears quite good, but this particular antibody is not a particularly good binder as KD is only 33 nM.
In last plot and antibody against an extracelluar domain of a surface protein in the botulism toxin is shown to be quite good with an affinity of 130 pM and a dissociation rate (koff) of 4.5x10-6 sec-1.
|system||range (nm)||KD (nM)||kon (M-1sec-1)||koff (sec-1)|
Results of pseudo-global two state binding model to the raw data in the figure. Fitted lines are shown in orange.