[Protein-analysis] Re: Enthalpy of protein

Frank Küster via proteins%40net.bio.net (by frank from kuesterei.ch)
Thu Mar 29 11:59:57 EST 2007


"Protenger" <yellowish from gmail.com> wrote:

> One of my fellows said "by introducing stabilizing interaction in
> proteins (in its core or surface) its enthalpy will increase"

That doesn't sound correct.  First of all, as has been pointed out, the
absolute enthalpy is both hard to get and quite boring.  The interesting
question, therefore: Which process is considered?  If it is complete
unfolding, then the quantity of interest is the enthalpy of
folding/unfolding.

> This sentence have confused me very much, because as I have learned
> before reactions (for example protein folding) tend to
> reduce their enthalpy by releasing heat so stabilized protein (native)
> relative to intermediate one (for example molten globule state) must
> have a lower enthalpy.

Err, are we talking about enthalpy or Gibbs (Free) enthalpy?

And what is it that confuses you?  Are you sure you were both talking
about the same process?  Naturally, if the (Gibbs) enthalpy of unfolding
decreases upon a mutation, the (Gibbs) enthalpy of folding will
increase.

> So what about engineered proteins that stabilized for example by
> introduced salt bridges?
> What is the deference between intrinsic (absolute) enthalpy between
> them?
> Or clearly, which of them has higher enthalpy?

Why are you interested in absolute enthalpies, when all that is
experimentally accessible is the change in enthalpy (or Gibbs enthalpy)
associated with a process?

Regards, Frank
-- 
But this:
> For fucks sake...
is just offensive.  It should have an apostrophe(!)
[MJ Ray, nowhere]


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