Protein-ligand interactions affinity measurements

Next to the detection of enzyme inhibition, ESI-MS can also be used to monitor protein-ligand interaction, employing an assay format similar to fluorescence-based receptor assays. Using a similar continuous-flow analytical screening system as shown in Fig. 5.2, a competitive assay can be set up using ESI-MS to measure the interaction of the analyte(s) with an affinity protein such as an antibody, receptor or enzyme [28]. Figure 5.10 shows the equilibrium reactions that form the basis of the assay concept. In a first step, the sample was injected into a con-... 

The dissociation constant or binding affinity, (with a unit of M), is the reciprocal of and is more frequently used (Eq. 11.6), wha-eas the binding affinity is a measure of the strength of the protein-ligand interaction. When the fi-ee protein and ligand reach the same value as the dissociation constant, 50% of the complex is formed ... 

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