Question

Energy and entropy: When a protein folds, it is able to lower its potential energy by making favorable electrostatic and hydrophobic/hydrophilic interactions. However, when you increase the temperature of its environment, you can cause the protein to unfold. Explain why the folded state is dependent on temperature.

Answer 1

ANSWER in denaturation involves a change Prote in the protein structure with the loss of activity. The free energy change on folding on anfololing is due to the combined I effects of both peotein folding / unfololing and bydration changes. There are both enthalpic and entropie contributions to this free energy that change with temperature and so give rise to heat denaturation and cold olenátwalion. Protein unfolding at higher temperatures is easily understood, but the widespread existence of protein unfolding at low temperatures is seaprising. 100 Protein % unfolded Temperature

T The midpoint temperatures of both heat and cold denaturation may be determined of the peaks in the temperature dependence of the heat copauty, where the intermediate Streuf Stuefuer oue absorbing the adobtional heat. The temperature lange is relatively narrow (~ 15°c) with the "molting temperature " (Tom) of the peétein de fined as the midpoint of the unfolding transition, where the Gribb's free energy of unfolding , A6100. The unfolding is due to the competition befun. the enthalpy of the hydrogen-bonding between aming and residues and the bydration Il amino and residues. The extent of the effect / kosmotropic and chao tropic flatur ons the protein stability has been found to depend on the water activity (an). 2/2