Energetic laser pulses (300 ?J- 2 mJ) have been utilized to excite absorptive dyes in solution. These dyes act as heat transducers, taking the optical energy and converting it to thermal energy. This thermal energy diffuses throughout the bulk solvent in ca. 100 ps, raising the temperature of the solvent on the order of 8-10 C. This phenomena has been utilized to induce conformational changes associated with unfolding in proteins. Ultrafast infrared probes have been developed to monitor the kinetics of these changes. Distinctive changes have been observed on a ns timescale in RNase A. Further modifications are being made to the apparatus to allow for observation of spectral changes on the ps to ms timescale. In addition, optical parametric generation of near-IR pulses are being generated. The pulses can pump solvent modes directly, creating temperature rise. Other protein candidates are being considered, in particular those which undergo cold ?naturation? such that we may observe changes associated with the folding processes.
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