Antibody-antigen interactions measured by surface plasmon resonance: Global fitting of numerical integration algorithms

The interactions between adenylate kinase (AK) and a monoclonal antibody ag ainst AK (McAb3D3) were examined by means of optical biosensor technology, and the sensograms were fitted to four models using numerical integration a lgorithms. The interaction of a solution of McAb3D3 with immobilized AK fol lows a double exponential function and the data fitted well to an inhomogen eous ligand model. The interaction of a solution AK with immobilized McAb3D 3 follows a single exponential function and the data fitted well to a pseud o-first order reaction model. The true association constants of AK binding to McAb3D3 in solution were obtained from competition BIAcore measurements. The difference in results obtained with solid-phase BIAcore and competitio n BIAcore may be due to rebinding of the dissociated analyte to the immobil ized surface. The results obtained with BIAcore are compared to those obtai ned by ELISA methods. We suggest that the best method for analysis of BIAco re data is direct, global fitting of sensorgrams to numerical integration a lgorithms corresponding to the different possible models for binding.