GE HEALTHCARE Biacore T100, Handbook

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Biacore T100 Software Handbook BR-1006-48 Edition AE
197
Thermodynamic analysis 10
10 Thermodynamic analysis
Biacore T100 supports automated measurement of kinetics or affinity at a
series of temperatures using the
Thermodynamics wizard (Section 4.5.4). In
addition to displaying the variation of kinetic and affinity constants with
temperature, the evaluation software extracts standard thermodynamic
parameters from the data.
10.1 Background
10.1.1 Equilibrium thermodynamics
For equilibrium thermodynamics, the van’t Hoff equation states:
Substituting in the expression
and rearranging gives:
A plot of ln K
D
against 1/T should thus be a straight line, with slope
Δ
H°/R and
intercept on the y-axis
Δ
S°/R.
This simplified relationship does not hold if the heat capacities of reagents and
products differ, since different amounts of energy will be required to raise the
temperature by the same amount on the two sides of the reaction. In such
cases, the plot of ln K
D
against 1/T is not linear, and the relationship becomes
where
Δ
G° is the standard free energy change
R is the universal gas constant
T is the absolute temperature (K)
K
D
is the equilibrium dissociation constant
where
Δ
H° is the standard enthalpy change
Δ
S° is the standard entropy change
Δ
G
°
RT
1
K
D
------
ln
–
RT K
D
ln
= =
Δ
G
° Δ
H
°
T
Δ
S
°
– =
K
D
ln
Δ
H
°
RT
----------
Δ
S
°
R
---------
– =