Yoctoliter thermometry for single-molecule investigations: A generic bead-on-a-tip temperature-control module

A new temperature-jump (T-jump) strategy avoids photo-damage of individual molecules by focusing a low-intensity laser on a black microparticle at the tip of a capillary. The black particle produces an efficient photothermal effect that enables a wide selection of lasers with powers in the milliwatt range to achieve a T-jump of 65 °C within milliseconds. To measure the temperature in situ in single-molecule experiments, the temperature-dependent mechanical unfolding of a single DNA hairpin molecule was monitored by optical tweezers within a yoctoliter volume. Using this bead-on-a-tip module and the robust single-molecule thermometer, full thermodynamic landscapes for the unfolding of this DNA hairpin were retrieved. These approaches are likely to provide powerful tools for the microanalytical investigation of dynamic processes with a combination of T-jump and single-molecule techniques. T-Jump: A simple and generic temperature control system is capable of achieving a large-scale temperature jump within milliseconds by focusing low-intensity lasers on black microparticles. The mechanochemical properties of a single molecule, such as a DNA hairpin molecule, are exploited to measure the temperature in a yoctoliter volume in real time.