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 conventionally studied by gel mobility shift assay. This technique gives us only qualitative information, we must label enzymes radioactive or fluorescent molecules, and it takes a relatively long time to analyze the results. Here we introduce a new tool of a highly sensitive 27 MHz quartz-crystal microbalance (QCM), in which the resonance frequency decreases linearly with the increase 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 solution. The results are also compared with those from a surface plasmon resonance sensor.