Automated 2D IR spectroscopy using a mid-IR pulse shaper and application of this technology to the human islet amyloid polypeptide

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   Fig. 1.

   Pulse sequences for different 2D IR methods. (a and b) The traditional pulse sequence for measuring 2D IR spectra by hole-burning with an etalon (a) and by a heterodyned photon echo (b). (c–e) The pulse sequences we implement here use pump pulses shaped to be a time-reversed etalon (c), a Gaussian (d), and a pulse pair (e).

   
   
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   Fig. 2.

   2D IR spectra of W(CO)₆ dissolved in hexane, obtained with pump pulses shaped as a traditional etalon (a), a time-reversed etalon (b), a Gaussian (c), and a pulse pair (d) for T = 2.0, 1.0, and 0.2 ps. Fifteen contours were drawn, from minimum to maximum of normalized intensities.

   
   
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   Fig. 3.

   FTIR and 2D IR spectrum of the amide I transition of hIAPP fibrils in D₂O. The 2D IR spectrum was collected by using the pulse-pair method, which was also phase-cycled to reduce scatter. The dotted line in the FTIR panel represents the spectrum of the probe pulse.