Figure 6. Phase-resolved chiral SFG spectra of LK₇β on quartz surface.

(a) (L-) LK₇β and (b) (D-) LK₇β. Chiral SFG spectra in the O-H/N-H region (~3200 cm⁻¹) of LK₇β prepared in H₂O and H₂¹⁸O and chiral SFG spectra in the O-D/N-D region (~2400 cm⁻¹) of LK₇β prepared in D₂O and D₂¹⁸O. All spectra are fit to Lorentzian lineshapes. Individual vibrational bands based on the fitting are shown in gray, and the sum of these peaks are shown in solid lines. Red or blue dashed lines indicate perturbation by ¹⁸O substitution for the highest (ω₁) and lowest (ω₄) vibrational bands that are assigned to water O-H stretching. The two middle (ω₂ and ω₃) bands are not impacted by ¹⁸O substitution and are assigned to protein N-H or N-D stretches. The parameters fitting the four spectra of (L-) LK₇β are comparable to those of (D-) LK₇β, except the phase of each vibrational band reverses. Adapted with permission from ref 3. Copyright 2020 National Academy of Science.