Direct FAC-MS Methods for Compound Binding Data

A plot of [A]q + y versus reciprocal breakthrough volume supports the determination of Bt and by linear regression analysis. As with all FAC methods for ligand characterization, the cartridge does not require precalibration before a measurement is made, because is a product of the measurement. One disadvantage of this method is that any error in the earlier measurements is carried forward in subsequent ones however the speed of these measurements and the ability to accurately measure Vq usually makes this the method of choice. 

These sorts of analyses are limited only by the ability of the chosen mass spectrometer to detect the test-compound under infusion-buffer conditions. In many cases, there will not be a problem even at low nanomolar compound concentrations, but in others MS will be hard-pressed to detect compounds even at micromolar concentrations. The online FAC-MS system will always be challenged by the inherent incompatibility of routine assay buffers with MS, but there are opportunities to reconfigure either the ion source or the buffer composition for 

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