Over 100°C

What factors contribute to protein stability at very extreme temperatures? What gain comes from entropy and enthalpy? And how to account for the delicate effect of temperature on molecular interactions like the hydrophobic and ionic ones? All this is tackled in a very intriguing work by Y. Matsura et al. "Thermodynamics of protein denaturation at temperature over 100°C: CutA1 mutant proteins substituted with hydrophobic and charged residues" recently published in Scientific Reports [see here]. By designing sequential mutations the authors were able to construct hyper-stable versions of the CutA1 protein and to extract the main thermodynamic parameters characterising their thermal stability. It is a very important work challenging both technical biochemical problems, like the aggregation of proteins generally occurring above 80°C, and the basic thermodynamics controlling protein stability over 100°C where for instance hydrophobic interactions cease to be entropically driven and ion-pairing can benefit from water dielectric constant decrease.