Casein Interactions Studied by the Surface Plasmon Resonance Technique

• Published in: Journal of dairy science 2002-11, Vol.85 (11), p.2711-2721
• Main Authors: Marchesseau, S., Mani, J-C., Martineau, P., Roquet, F., Cuq, J-L., Pugnière, M.
• Format: Article
• Language: English
• Subjects: Adsorption; Analytical, structural and metabolic biochemistry; BIACORE; Biological and medical sciences; bovine casein; Calcium - chemistry; Calcium - pharmacology; casein interaction; Caseins - chemistry; Caseins - metabolism; Chromatography, Gel; Food industries; Fundamental and applied biological sciences. Psychology; General aspects, investigation methods; Hydrogen-Ion Concentration; Kinetics; Milk and cheese industries. Ice creams; Osmolar Concentration; Phosphorylation; Proteins; Static Electricity; surface plasmon resonance; Surface Plasmon Resonance - methods
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.S0022-0302(02)74358-0

Surface plasmon resonance technique was investigated for the first time to study the apparent hydrophobicity and association properties of the major bovine caseins: αs-(αs1- and αs2-caseins in a 4:1 proportion),β-, and κ-caseins. The apparent hydrophobicities of the caseins were evaluated by a new method based on the binding level of casein on a hydrophobic sensor chip, and kinetic and equilibrium affinity constants were determined for the following casein interactions: αs/αs, αs/β, αs/κ, β/β, and β/κ, using a sensor chip modified with covalent immobilized caseins. The study by surface plasmon resonance technology of these casein interactions under different conditions (pH, ionic strength, calcium concentration, chemical modification) demonstrated that, at neutral pH, electrostatic repulsive forces play an important role since an increase in ionic strength of the medium resulted in a stronger interaction. When charge repulsions were reduced by either acidification, increase in ionic strength, or dephosphorylation, casein interactions were reinforced, presumably due to weak attractive forces. Moreover, in this molecular model, we showed that addition of calcium greatly increased the binding response between the most phosphorylated caseins and that the added calcium (2mM) participated directly in the formation of bridges between the phosphate groups of the casein molecules.