Proteins entropy, inverse temperature

Figure 2.8. Ordered water molecules surround oillike groups, as first shown by Stackelberg and Muller. As oil-like groups associate, this structured water becomes less ordered liquid water this is the large positive change in entropy responsible for the inverse temperature transition, the phase transition that is fundamental to protein function. As shown in the upper left, hydration of a proximal carboxylate...

Inverse Temperature Transitions Provide Negative Entropy to Protein... 

The inverse temperature transition is a specific mechanism whereby thermal energy (heat) provides an increase in order of the protein part of the system. A decrease in entropy of this sort has been termed negative entropy by Schrodinger. ° While the total entropy (disorder) for the complete system of protein and water increases as the temperature is raised, the structural protein component, critical to the conversion of thermal energy to mechanical work, increases in negative entropy. The protein component increases in order by the folding that shortens length and by the assembly of oillike domains that builds structures. 

Despite the absorption of heat for the transition and the overall increase in entropy of -(-4.0 EU for the water plus protein, the protein component actually increases in order on raising the temperature. As unambiguously demonstrated by crystallization of a cyclic analog (see Figure 2.7), in this case the protein component of the water plus protein system becomes more ordered as the temperature is raised. For this and additional reasons, noted below in section 5.1.3, we call this transition exhibited by our model protein, poly (GVGVP), an inverse temperature transition. 

Formation of hydrophobic hydration is exothermic (Butler, 1937). Accordingly, when the temperatiure of the dissolved protein with its hydrophobic hydration is raised from below to above the inverse temperature transition, an endothermic transition due to the conversion of hydrophobic hydration to bulk water occurs. The transition from hydrophobic hydration to bulk water represents a positive change in entropy. By finding a suitable solvent that allows the transition but reduces the heat of the transition to near zero, it becomes possible to determine whether a decrease in elastic... 

---