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Enthalpy of antibody--cytochrome c binding
C S Raman1, M J Allen, B T Nall
1Department of Biochemistry, University of Texas Health Science Center, San Antonio 78284-7760, USA.
Biochemistry
|May 2, 1995
Summary
High-sensitivity titration calorimetry reveals distinct binding thermodynamics between monoclonal antibodies (MAbs) and cytochrome c. Differences in heat capacity suggest varied binding modes and highlight factors beyond hydrophobicity in antibody-antigen interactions.
Area of Science:
- Biophysical Chemistry
- Immunology
- Protein-Ligand Interactions
Background:
- Cytochrome c is a crucial protein in cellular respiration.
- Monoclonal antibodies (MAbs) are vital tools in research and therapeutics.
- Understanding antibody-antigen binding thermodynamics is key to characterizing molecular recognition.
Purpose of the Study:
- To quantify the thermodynamic parameters of monoclonal antibody binding to cytochrome c.
- To investigate the influence of distinct binding sites on binding thermodynamics.
- To elucidate the contributions of enthalpy, entropy, and heat capacity to antibody-antigen interactions.
Main Methods:
- High-sensitivity titration calorimetry was employed to measure binding.
- Enthalpy, heat capacity, and protonation changes were determined.
- Association rate constants were analyzed.
Main Results:
- Two MAbs, 2B5 and 5F8, bind to different sites on cytochrome c with high affinity.
- MAb 2B5 binding involves proton uptake, while MAb 5F8 binding does not.
- Significant differences in the temperature dependence of enthalpy (ΔCp) were observed between the two MAbs, suggesting distinct binding mechanisms.
Conclusions:
- The binding of MAbs to cytochrome c exhibits distinct thermodynamic profiles.
- Differences in ΔCp indicate variations in the buried molecular surfaces and binding modes.
- Factors beyond hydrophobic effects likely contribute to the thermodynamics of these antibody-cytochrome c interactions.