The Michael Gross group intersects two lasers: the first is a temperature jump at 1900 cm-1(IR) to heat a flowing solution containing a protein and perturb its folding. The second at 248 nm (UV) is an FPOP probe generating OH radicals that footprint the folding state of the protein on the microsec time scale. For a description of this work, see: T-jump and Fast Photochemical Oxidation Probe Sub Millisecond Protein Folding, Jiawei Chen, Don L. Rempel, Michael L. Gross, J. Am. Chem. Soc. 132, 15502–15504 (2010).