The KinExA 3000, manufactured by Sapidyne Instruments, is designed for the measurement of equilibrium and kinetic parameters via kinetic exclusion assay (KinExA) methods. This method utilizes a combination of specialized fluidics and optics to ensure reliable and accurate results. What separates this instrument from other instruments is its flow cell technology. Typically, a major problem with measuring concentration or kinetic parameters is that the process of measuring often distorts the solution concentration. The theory behind the KinExA method is that the measurement must be reported before that action perturbs the solution (e.g. kinetically excluding changes in concentration by limiting exposure time to less than a receptor-ligand dissociation time). This instrument controls exposure time via flow cell technology that minimizes the time samples and reagents pass over the solid phase. A small column with a solid phase is used with a flow rate that is controllable between 50 milliseconds and about one second to measure solution parameters.
The KinExA method is ideal for defining any parameter in affinity and kinetics. As one example, Kd measurements are very accurate due to free receptor concentration not being affected by measurement. In addition to being an effective tool for solution chemistry, this instrument has proven to be a valuable immunoassay platform. Sensitivity in assay methods such as ELISA can suffer due to competition at the ligand/antibody sites. Kinetic exclusion assays, however, avoid this competition and maximize sensitivity to be 10 – 1000 fold more than ELISA when using the same reagents. This opens numerous applications in immunobiology, primarily those including the characterization of antigen-antibody interactions. Because of this sensitivity, antibodies with very low affinities can be successfully investigated and characterized, and can be run using either recombinant or unpurified native antigens. Beyond sensitivity, flexibility permits a variety of techniques to be used, including reverse assay and whole cell binding.