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Desperate Need of Help

  1. Sep 24, 2006 #1
    Desperate Need of Help!!!

    I've done my homework (except one problem) and I want to make sure I am correct?

    1. What is the sign (delta G) for the folding process? Unfolding? How do you know?
    -(delta G) at low temp is positive and equilibrium will favor protein folding. At high temperature, delta G is negative and unfolding occurs because strong increase of change of entropy that lowers Gibbs free energy.

    2. What is the sign for (delta S) “ “
    -Unfolding (delta S) is positive and folding is negative because breaking of favorable interactions holding the folded protein will need input of energy , and delta H will increase also. When temperature increases, randomness increases and denaturation occurs at high temperature. Folding is in relation to decrease in randomness (at low temperature) and becomes more ordered.
    3. What will contribution of delta S to the free energy change be positive or negative? What does this mean?

    4. What are the main bonds and interactions that must be broken or disrupted is a folded polypetide is to be unfolded? Why does heat or ph cause unfolding?
    -H-bonds, disulphide, salt bridges, and hydrophobic interactions are disrupted. If heat is added, vibrational modes in the molecule will be excited and will disrupt hydrophobic interactions and dipole-dipole interactions and denature protein. If ph were to change, the protonation state of amino and carboxyal groups change and ionic bonds in the proteins disrupt and disrupts salt-bridges.
  2. jcsd
  3. Sep 24, 2006 #2


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    Staff: Mentor

    Biochemistry is not my area, although I do find it fascinating. Nevertheless, I found this. http://en.wikipedia.org/wiki/Protein_folding
    If a process if spontaneous, what is the sign on Gibbs free energy?

    Protein structure forces, and folding pdf file.


  4. Sep 24, 2006 #3
    Thank you very much!

    Can you interpret question 3 for me?:
    3. What will contribution of delta S (entropy) to the free energy change be positive or negative?
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