Free energy and irreversible processes

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The discussion revolves around the challenge of assessing the thermal stability of a protein that unfolds irreversibly, complicating the use of Gibbs free energy calculations typically based on reversible processes. The user inquires whether Gibbs free energy can be defined for irreversible processes and how to calculate it without an equilibrium constant. They mention their current approach of analyzing kinetics and obtaining an Arrhenius activation energy. A suggestion is made to use an alternative equation involving changes in enthalpy and entropy to estimate Gibbs free energy. The conversation emphasizes the need for methods to evaluate thermal stability in irreversible unfolding scenarios.
arwelbath
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Hi,
I'm working on a problem of the thermal stability of a protein. Conventionlly, people compare protein thermal stability in terms of the Gibbs free energy difference between the native and unfolded state. So if it reversibly falls apart, then for N <==> U, DG(N-U) is accessed from the classical equilibrium constant for the process. (DG = -RT ln K)

But, unfortunately my system unfolds irreversibly so that N --> U.

Is the gibbs free energy defined for an irreversible process? If so, how can it be calculated without an equilibrium constant? If it's not defined, is there an equilvalent quantity which can be used?

The best I can do so far is to look at the kinetics, which I've done and got an Arrhenius activation energy. Can I get any more information from this?

Please Help!
 
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I'm pretty sure you can find delta G by using the equation
delta G = (delta H) - delta(TS) --> delta G = (Cp * delta T) - (TfSf - TiSi)

Hope this helps
 
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