QCM-D study of molecular conformational effects on protein - DNA interactions

Quartz Crystal Microbalance with Dissipation (QCM-D) monitoring is a surface sensitive technique for assessment of mass and viscoelastic properties of thin films. It is commonly used for evaluation of binding and interactions of biological molecules in liquid environment. Since the QCM-D working principle is based on lateral movement of a quartz sensor, both deposited biomolecules and associated water, are coupled to the sensor motion. Therefore, the output data describes hydrated films, where frequency of the sensor movement (∆f) reflects film mass, and damping of the movement (∆D) correlates to viscoelastic properties. In contrast, surface analytical techniques based on optical principles, such as Surface Plasmon Resonance (SPR), can only sense the biomolecules and omit the surrounding medium. By complementing QCM-D data with information from SPR, parameters such as film hydration and density can be accurately calculated. Furthermore, with the QTools* modeling software film thickness, viscosity and elasticity can be determined. This application note describes capability of QCM-D technology to characterize protein – DNA interactions.