The equilibrium constant for the interaction between a monoclonal Fab fragment and an influenza virus neuraminidase.

The affinity or equilibrium constant between an Fab fragment derived from monoclonal IgG directed against influenza virus neuraminidase was measured as 4.1 X 10(7) M-1. The method, which makes use of an air-driven ultracentrifuge, is simple and uses extremely small amounts (10(-11) mol) of material. Furthermore, interpretation of the data is based on sound theoretical considerations. The technique also allows m.w. of the interacting species to be measured and the stoichiometry of the reaction to be determined.