Temperature control device for single molecule measurements using the atomic force microscope

Abstract

The design and implementation of a temperature control device for the atomic force microscope (AFM) are described. This device is based on a thermoelectric module which can be used for both heating and cooling the samples in the AFM liquid chamber within the range of 5–50°C. A thermocouple is inserted in the liquid chamber to measure the sample temperature. A commercial thermoelectric temperature controller is used to keep the temperature constant during a measurement, which can be stabilized within 0.1°C. To dissipate the heat generated by the thermoelectric module during cooling, a water cooled heat sink is used. Using this device, imaging and mechanical unfolding experiments were carried out at different temperatures. The results show that the temperature control device does not significantly reduce the imaging capacities of the AFM, and that the force-induced unfolding of individual protein molecules can be readily observed at different temperatures. Temperature dependent single molecule measurements can broaden the applications of AFM and reveal new insights into the macromolecular structures and processes.