Time-resolved vibrational spectroscopy is an important tool for understanding biological processes and chemical reaction pathways . Today, all available methods to our knowledge require many repetitions of an experiment to acquire a microsecond time-res. mid-IR spectrum.
We present the IRspectrometer, a quantum cascade laser dual frequency comb spectrometer [2-3]. It allows for parallel acquisition of hundreds of mid-infrared wavelengths with microsecond time resolution. The formation of the light-activated L, M and N-states in bacteriorhodopsin – which only have µs to ms lifetimes – has been recorded that show the infrared response of bacteriorhodopsin to 10 ns visible light pulses with microsecond time-resolution. The different wavelengths were all measured in parallel thanks to the dual-comb approach. The spectra as well as the kinetics show good agreement with those from step-scan FT-IR measurements. As a benchmark, the spectral signature of several intermediate states of the bacteriorhodopsin photocycle has been recorded in a single shot measurement. This approach greatly reduces the complexity of time-resolved bio-spectroscopy measurements in the mid-infrared which currently require many repetitions.
Markus Geiser, Jessica L. Klocke, Markus Mangold, Pitt Allmendinger, Andreas Hugi, Pierre Jouy, Balint Horvath, Jérôme Faist, and Tilman Kottke, "Single-shot microsecond-resolved spectroscopy of the bacteriorhodopsin photocycle with quantum cascade laser frequency combs (Conference Presentation)," Proc. SPIE 10685, Biophotonics: Photonic Solutions for Better Health Care VI, 106852G (Presented at SPIE Photonics Europe: April 26, 2018; Published: 24 May 2018); https://doi.org/10.1117/12.2306831.5789228724001.
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