QUESTIONS: alpha-helix "signals" in proteins
Simon Brocklehurst Bioc
smb18 at mole.bio.cam.ac.uk
Wed Jul 6 13:10:49 EST 1994
sre at al.cam.ac.uk (Sean Eddy) writes:
>In article <2veoju$dur at lyra.csx.cam.ac.uk> smb18 at mole.bio.cam.ac.uk (Simon Brocklehurst (Bioc)) writes:
> >1) There is no thermodynamic (!!) advantage for main-chain polar groups
> > to make intramolecular hydrogen bonds rather than to make hydrogen
> > bonds with solvent -- is there?
>I've always thought that there was a favorable entropic term. If you
>make intramolecular H-bonds, you free up a lot of individual water
>molecules that would otherwise be constrained. Even though the newly
>freed waters go and H-bond to other waters in solution (so there's no
>significant enthalpic contribution) it seems like the number of
>degrees of freedom in the system increase, so the entropy increases.
>Is this wrong?
But the protein chain becomes more constrained when it forms
intramolecular hydrogen bonds, compared to when it is making
h-bonds with solvent.
>- Sean Eddy
>- MRC Laboratory of Molecular Biology, Cambridge, England
>- sre at mrc-lmb.cam.ac.uk
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