The “nonequilibrium" experiment, in which a system-of-interest is perturbed away from its natural, relaxed state, often unveils fundamental mechanisms invisible to mere observation: Enzymes rapidly mixed with their substrates divulge how biological reactions are initiated; retinal, the molecule responsible for animal vision, can no longer hide its critical structural changes when manipulated by pulsed laser illumination; chemical reactions triggered by electrical currents reveal the first moments of atomic exchange. However, the nonequilibrium experiment is often hindered by the necessity of finding highly specific “triggers" to affect the system in question.
We have developed a novel tool termed Diffusion Nanoscale Temperature-Shift (DINT), which generalizes the concept of a nonequilibrium measurement. Specifically, DINT enables the extremely rapid generation of heat at the scale of one hundred nanometers, providing a general trigger — temperature — with which to manipulate nearby molecular species and observe their subsequent dynamics.
In our first completed work, DINT was used to provide an unprecedented confirmation of “hot Brownian motion" (HBM), the enhanced diffusion of an entity held at a higher temperature than its surroundings. These experiments not only validated the theoretical underpinnings of HBM, but they also hinted at a greater significance of “temperature" at the nanoscale. Importantly, this work has also set the stage for future nonequilibrium measurements of single biomolecules. By allowing direct, rapid and generalizable nonequilibrium perturbations, such experiments will shed insight into the various dynamic motions and conformations that endow biomolecules with their life-sustaining abilities.