When working with cell lines, assessing the expression level of target receptors on the cell surface becomes a critical parameter for interpreting the outcomes of functional assays and determining receptor occupancy levels in dose-response studies. Traditional methods often require calibration and laborious protein purification, adding complexity and cost to the process. However, our Membrane-Protein Affinity and Concentration (MAffCon) Assay simplifies this by directly working with membrane proteins derived from cells and providing a straightforward approach to measure expression levels, all without the need for purification, immobilization, or extensive assay optimization.