Ultra-sensitive microwave detection of protein conformational changes

A coaxial driven planar slot antenna resonant in the microwave regime was used to detect changes in protein conformation induced by temperature modulation. Simultaneous dielectric and UV/VIS spectroscopy measurements were obtained by attaching the slot antenna to a fused-quartz UV/VIS sample holder. Similar thermodynamic parameters (midpoint temperature and enthalpy) were obtained from both techniques over a wide concentration range and under a variety of pH condition. Here we demonstrate that a near-field antenna can be used to detect changes in conformation at very low protein concentrations, and that the protein is not destabilized by the presence of microwave power.