Isothermal titration calorimetry

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SUMMARY

This discussion focuses on calculating the standard entropy change (\Delta S^{0}_{bind}) for a protein-ligand binding reaction at 37°C using isothermal titration calorimetry (ITC). The user successfully determined the standard Gibbs free energy change (\Delta G^{0}) to be -12300.1 cal/mol at 25°C and utilized the van't Hoff equation to relate temperature changes to binding constants (K_d). The binding enthalpy (\Delta H^{o}_{bind}) was established at -5000 cal/mol. The user concluded that the van't Hoff equation is essential for deriving \Delta S^{0}_{bind} at the elevated temperature.

PREREQUISITES
  • Understanding of isothermal titration calorimetry (ITC)
  • Familiarity with thermodynamic equations, particularly the van't Hoff equation
  • Knowledge of Gibbs free energy (\Delta G) and its relation to binding constants (K_d)
  • Basic principles of protein-ligand interactions
NEXT STEPS
  • Study the van't Hoff equation and its applications in thermodynamics
  • Learn about the calculation of binding constants (K_d) from ITC data
  • Explore the relationship between enthalpy (\Delta H) and entropy (\Delta S) in biochemical reactions
  • Investigate advanced topics in isothermal titration calorimetry, including data analysis techniques
USEFUL FOR

Researchers in biochemistry, biophysics, and molecular biology, particularly those involved in studying protein-ligand interactions and thermodynamic properties of biomolecules.

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Homework Statement



Using isothermal titration calorimetry, you calculate \DeltaH^{o}_{bind} (= -5000 cal/mol) for a protein-ligand binding reaction at 25°C. You then perform a separate assay in which you measure equilibrium ligand binding at two different temperatures:

L_{0} (nM) Ceq (nM) at 25°C Ceq (nM) at 37°C
0.01 :: 0.007 :: 0.006
0.03 :: 0.021 :: 0.017
0.1 ;: 0.070 :: 0.058
0.3 :: 0.197 ;: 0.166
1 :: 0.537 :: 0.439
3 ;: 0.830 :: 0.778
10 :: 0.943 :: 0.930
30 :: 1.002 :: 0.964
100 :: 0.981 :: 1.009

What is \DeltaS^{0}_{bind} at 37C

Homework Equations


\DeltaG^{0}=RTlnK_{D}

\DeltaG=\DeltaG^{0} + RTln[L]_{eq}/[P]_{eq}[L]_{eq}

\DeltaG=\DeltaH-T\DeltaS


The Attempt at a Solution



I can find K_{d} graphically and therefore find \DeltaG^{0} to be -12300.1 cal. At the same temperature, \DeltaG^{0}=\DeltaG at 25C, so i can find \DeltaS at 25C. But I don't know how this helps me find \DeltaS^{0}_{bind} at 37C or if this helps me at all.

thanks for any help or direction
 
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never mind, I think i figured it out using the van't hoff equation to find delta H at 37C since I can find the different Kds and am given the different temperatures.