Thermodynamic parameters for beta-lactoglobulin dissociation over a broad temperature range at pH 2.6 and 7.0

• Published in: Thermochimica acta 2000-08, Vol.359 (2), p.181-188
• Main Authors: Owusu Apenten, Richard K, Galani, Despina
• Format: Article
• Language: English
• Subjects: Analytical, structural and metabolic biochemistry; Animal, plant, fungal and microbial proteins, edible seaweeds and food yeasts; Beta-lactoglobulin; Biological and medical sciences; Dissociation; Food industries; Fundamental and applied biological sciences. Psychology; Glycoproteins; Protein stability; Proteins; Thermodynamics
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/S0040-6031(00)00523-2

Thermodynamic parameters were determined for the dissociation of beta-lactoglobulin(β-Lg) at temperatures from −15 to 85°C. The effect of temperature on K d (equilibrium constant for dimer ⇌ monomer dissociation) was described by a second-order Van’t Hoff equation (ln K d= AT −2+ BT −1+ C) or Gibbs–Helmholtz equation. The Gibbs free energy (Δ G), enthalpy (Δ H), entropy (Δ S) and thermal capacity (Δ C p ) for β-Lg dissociation were evaluated. At 25°C standard temperature thermodynamic parameters were Δ G 0=24.8 (±0.35) kJ mol −1, Δ H 0=57 (±13) kJ mol −1, Δ S 0=92 (±30) J mol −1 K −1 and Δ C p =2383 J mol −1 K −1 at pH 2.6. For β-Lg dissociation at pH 7, Δ G 0=28.6 (±2.7) kJ mol −1, Δ H 0=107.5 (±6.3) kJ mol −1, Δ S 0=265.7 (±39) J mol −1 K −1 and Δ C p =2383 J mol −1 K −1. Simulated temperature–dissociation profiles of β-Lg show that the fraction of dissociated protein increases with increasing temperature, decreasing pH and with decreasing protein concentration.