Figure 5

H/D exchange in D ₂ O-dissolved lysozyme. Note that there is an oscillation here as well, like in membranes, between the ISO and the ΔT difference spectra both in the intensity (panel A) and the frequency (panel B) of the disappearing amide II frequency, but this oscillation disappears at the maximal H/D exchange rate (the exchange rates became so small that the frequencies could not be determined any more). In lysozyme, H/D exchange is not leading to protein heat-denaturing. Here, H/D exchange involves only reversible protein movements, the irreversible denaturing happens only at much higher temperatures.