A highly sensitive 27 MHz quartz-crystal microbalance as a device for kinetic measurements of molecular recognition on DNA strands

DNA-DNA hybridization and DNA-protein or enzyme interactions are essential steps in biomolecular recognitions. These interactions have been convention ally studied by gel mobility shift assay. This technique gives us only qual itative information, we must label enzymes radioactive or fluorescent molec ules, and it takes a relatively long time to analyze the results. Here we i ntroduce a new tool of a highly sensitive 27 MHz quartz-crystal microbalanc e (QCM), in which the resonance frequency decreases linearly with the incre ase of mass on the electrode area at the nanogram level. Thus, when a host molecule is immobilized on a QCM, the binding behavior and its kinetics can be monitored from frequency changes due to the guest binding in aqueous so lution. The results are also compared with those from a surface:plasmon res onance sensor.