MS-based ligand binding assays with speed, sensitivity, and specificity.

Immunoassays are widely used in biochemical/clinical laboratories owing to their simplicity, speed, and sensitivity. We combined self-assembled monolayer-based immunoassays with MALDI-TOF MS to show that high-fidelity surface preparations with a novel matrix deposition/crystallization technique permits quantitative analysis of monolayer-bound antigens at picomolar detection limits. Calibration curves for intact proteins are possible over a broad concentration range and improved specificity of MS-immunoassays is highlighted by simultaneous label-free quantitation of ligand-bound protein complexes.