QCM: Quartz Crystal Microbalance

A Quartz Crystal Microbalance enables the detection of mass variation by measuring the change in frequency of a quartz crystal resonator (the sensor). When molecules bind to the surface, the thickness of the crystal changes and this translates into a drop in frequency. The device can be used for example to study molecular interactions between proteins and other molecules such as proteins or DNA and also living cells. Ligand-analyte interactions can be measured by functionalizing the sensor surface via ligand binding.

What are the sample requirements?

  • Sample volume of the measuring cell is about 30-40 µl.
  • For static state measurements, around 100 µl is needed to exchange the liquid inside the cell.
  • Protein concentrations of around 1 mg/ml is used for surface functionalization with the ligand.
  • Analyte concentration can be much lower, e.g. around 0.1 mg/ml.

What other specific considerations are relevant?

  • Purity of the ligand (molecule attached to the sensor chip) should be as high as possible, to prevent unspecific binding.
  • Knowing the molecular weight of the analyte is important since the sensor detects the changes of mass on the surface
  • If possible, viscous buffers should be avoided as they interfere with the QCM sensor.
  • Buffers and samples should withstand degassing by vacuum.

Partners offering this technique

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