From: Jack Correia <jcorreia@umsmed.edu>
  To  : csaez <csaez@CCTR.UMKC.EDU>
  Date: Mon, 18 Aug 1997 15:35:57 -0500

Re: Van't Hoff Plots ...

Cristian Saez


        Fitting a nonlinear plot to a quadratic is not very informative?
There is a lot of published work on the interpretation of nonlinear van't
Hoff plots - your comments suggest you do not know about them!  Do a full
search & read more about it.  Exciting times in this area right now!  I
provided an off the "top" list below.  The functional form of the fitter
usually comes in two flavors - truncated van't Hoff or a form that uses
references states.  Protein denaturation at 20 C?

Vulevic & Correia (1997) Biophys J72: 1357-1375
        Discussion fitting & interpretation of curved van't Hoff plots for
microtubule assembly - uses the truncated form - references a paper by
Johnson that observed two straight lines with a sharp break - molecular
interpretation possible because the reaction mode probably changes!

Chaires (1997) Biophys Chem 64:15-23 - the issue on the 10th anniversity of
the Gibbs Conference - discusses difficulty in estimating deltaCp < |200
cal/mol/T|.  Read the whole issue!

Burz & Ackers (1996) Biochemistry 35:3341 - XLA self-association study of
lambda cI repressor where a sharp break occurs - uses reference states model 

recent papers by Spolar & Record - interpret heat capacity changes in terms
of buried surface in the complex - see Kip Murphy's work for an alternate
approach! 

Eftink et al (1983) Biochemistry 22:3884-3896 - curved van't Hoff plots can
also come from coupled equilibria - even protonation reactions can cause it!


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|   Dr. Jack Correia                                    |
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