Temp & Ab binding

Brian M. Baker brian-baker at uiowa.edu
Mon Apr 1 18:58:35 EST 1996

In message <4jmtp5$1d0 at news.iastate.edu> - baker at iastate.edu (Wayne R. Baker)
:>In bionet.molbio.proteins,  Louis Hom <lhom at nature.berkeley.edu> wrote
:>:A theoretical question on protein-protein interactions:
:>:	What effect would one expect temperature to have on binding
:>:strength between two proteins, say an antibody and a protein?  Is it the
:>:exact same model as the hydrophobic effect in protein folding, or is it
:>:different since it involves the solvent-exposed surfaces of the molecules?
:>  Depends on what drives the interaction. For any association, 
:>    dG = dH - T*dS
:>  Free energy as a function of temperature will therefore depend on how
:>the energy is partitioned between enthalpy and entropy. 
:>Wayne Baker (baker at iastate.edu)  	He who has a why to live for
:>4288 Molecular Biology Building  	can bear almost any how.
:>Iowa State University            	--Nietzsche

Depends on the enthalpy change for the reaction.  The Van't Hoff equation

(dlnK/dT) = DH/(RT^2)

leads to the temperature dependence of the equilibrium constant

K2 = K1*exp(-(DH/R)*((1/T2)-(1/T1)))

Check out Eisenberg & Crothers (Physical Chemistry w/ Applications to the Life
Sciences), chapter 4, specifically pages 158 - 160.  This is also covered
fairly well in Atkins.

To address the original poster, the temperature dependence would depend on the
sign and magnitude of the enthalpy change for the reaction.  With some
caveats, DH for binding reactions can be approximated from the change in polar
and apolar surface area using parameters derived from protein unfolding data. 
To this extent, association is similar to protein folding.


Brian M. Baker                             	      brian-baker at uiowa.edu
Graduate Student Peon              
Protein Structural Energetics       "I am becalmed and virtured, lost
Department of Biochemistry               to nothing on a bay of dreams..."
University of Iowa                                    -Blue Oyster Cult

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