Fig. 5. Inverted second-derivative infrared spectra of muscle-type lactate dehydrogenase (A₄-LDH) across the amide I region. Each panel shows spectra 2, 7, 12, 17, 25, 40 and 60 min after addition of protein to 75% D₂O buffer. Peaks in the spectra correspond to specific secondary structures, and the arrows at approximately 1655 cm^-1 (-helix) and approximately 1639 cm^-1 (ß-sheet) indicate the direction of change in peak height over time. d²A/dx², to be defined.