Isothermal titration calorimetry

Click For Summary
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.

Quickdry135
Messages
10
Reaction score
0

Homework Statement



Using isothermal titration calorimetry, you calculate [tex]\Delta[/tex]H[tex]^{o}_{bind}[/tex] (= -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[tex]_{0}[/tex] (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 [tex]\Delta[/tex]S[tex]^{0}_{bind}[/tex] at 37C

Homework Equations


[tex]\Delta[/tex]G[tex]^{0}[/tex]=RTlnK[tex]_{D}[/tex]

[tex]\Delta[/tex]G=[tex]\Delta[/tex]G[tex]^{0}[/tex] + RTln[L][tex]_{eq}[/tex]/[P][tex]_{eq}[/tex][L][tex]_{eq}[/tex]

[tex]\Delta[/tex]G=[tex]\Delta[/tex]H-T[tex]\Delta[/tex]S


The Attempt at a Solution



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

thanks for any help or direction
 
Physics news on Phys.org
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.