Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Free energy and irreversible processes

  1. Sep 30, 2004 #1
    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!!
  2. jcsd
  3. Sep 30, 2004 #2
    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
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook