Characterization of a human pancreatic secretory trypsin inhibitor mutant binding to Legionella pneumophila as determined by a quartz crystal microbalance.

We describe the isolation from a large phagemid library of a human pancreatic secretory trypsin inhibitor (hPSTI) mutant that binds to Legionella pneumophila. To gain further insight into the binding kinetics of the isolated hPSTI mutant, an immunosensing system based on a quartz crystal microbalance (QCM) was used. In contrast to ELISA procedures, k(on) and k(off) rates could be derived from the QCM sensograms. Thus, it is possible to characterize specific intermolecular interactions between proteins and phages isolated from large phage display libraries by QCM.