MadSci Network: Chemistry
Query:

Re: Hydrogen bonds in macromolecules as statistical bonds

Date: Thu Nov 19 09:52:45 1998
Posted By: Dan Berger, Faculty Chemistry/Science, Bluffton College
Area of science: Chemistry
ID: 910983067.Ch
Message:

Hydrogen bonds are said to be statistical bonds, with 10-11 s half-life. If we suppose that for 1 second, there is no energy available from the environment to rebuild these bonds, what would happen in macromolecules: implosion, explosion, something else? (Let's consider residual energy of breaking energy H bonds not sufficient for rebuilding bonds during 1 second.)


Unfortunately you can't have it both ways. Hydrogen bonds have a strength of about 10 kcal/mol, 10% of the strength of a typical covalent bond to hydrogen. If you have enough environmental energy to break hydrogen bonds, there's enough vibrational energy available for the molecule to reform them.

If you don't have enough energy for the molecule to do the hydrogen-bond shuffle, you won't have enough to break the hydrogen bonds.

On the other hand, putting in too much energy is very destructive. When you cook egg whites, the proteins are "denatured." This means that the hydrogen bonds which hold the protein in its active, folded form are broken, and the molecule is thrashing about so violently that they can't reform. Because protein folding is a somewhat delicate process, proteins once denatured often can't re-fold; this can be seen by the fact that egg whites don't turn clear and liquidy again when you take them out of the frying pan, even if you soak them in water.

Denaturing is also probably what would happen if you grant the miraculous energy removal posited by your question.

  Dan Berger
  Bluffton College
  http://cs.bluffton.edu/~berger


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