[Protein-analysis] Re: Enthalpy of protein

Protenger via proteins%40net.bio.net (by yellowish from gmail.com)
Tue Mar 27 04:12:54 EST 2007


On Mar 26, 10:37 am, Frank Küster <f... from kuesterei.ch> wrote:
> "Protenger" <yellow... from gmail.com> wrote:
> > Hello
> > I have a very simple question.
> > Suppose in a protein folding pathway we have two opposite charged
> > residues seperated by "d" angstrom such that there is a weak
> > interaction between them. We name it state A, so its enthalpy is Ha.
> > As protein conformation changes through folding pathway we suppose "d"
> > decreases, so interaction between charges become stronger. Now we name
> > it State B and its enthalpy as Hb.
>
> > My simple question is: is Ha>Hb? or Hb>Ha?
>
> Well, in vacuum or even in pure water it's easy to answer, isn't it?
> (Unless you are actually asking for signing conventions for
> thermodynamic quantities.)
>
> In reality, you've got buffer ions around, which (in either of the two
> states) might or might not be able to sit near one of the charges, and
> sit either quite statically "bound", or just have a higher average
> probability of being there.  Moreover, at least one of the states will
> be partially folded and hence can only be treated as an ensemble of
> structures: Then one single distance d cannot be meaningfully assigned,
> it should be treated as a distribution of distances with a dynamic
> exchange of substates.
>
> Does that help to confuse you? ;-)
>
> Regards, Frank
> --
> But this:> For fucks sake...
>
> is just offensive.  It should have an apostrophe(!)
> [MJ Ray, nowhere]

Tanks for your reply
I ask my question in another format.
Suppose we have a native protein with its own intristic (absolute)
enthalpy, then by protein engineering we introduce a pair
of opposide charged residues on its surface so its stability
increases.
Does absolut (and not delta H) enthalpy of mutant decrease?

regards
rahim



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