According to Eq., a van’t Hoff plot

According to Eq., a van’t Hoff plot, i.e., of R ln K versus 1/T,would yield from its slope ΔH , and from its intercept ΔS. There is, however, a difficulty, sine ΔH and ΔS generally depend on temperature in the case of protein unfolding, as illustrated in Figure 7.5. ΔH. Can also be determined by DSC (differential scanning calorimetry:see Figure 6.25 for an explanation). The example given in Figure 7.6a shows a sharp peak in heat uptake, almost like a melting transition. When results from a van’t Hoff plot and DSC can be compared, good agreement is mostly observed for single - domain proteins ( within 5% or so ). From such results and the observed denaturation temperatures, and with some interpolation,values for ΔH and ΔS can be derived as a function of temperature, to obtain curves like those in Figure 7.5.
Figure 7.4 shows that the transtion N→U occurs over a very small range of the variable applied. This is typical for a copperative transtion,where several bonds are broken ( or formed ) simultaneously. In other words, the molecule would either be in the native or in a (nearly ) fully unfolded state. Also the narrowness of the peaks on DSC plots (Figure 7.6 ) points to a copperative transition. For the unfolding at high temperature.