Spectroscopic and docking studies on the interaction between caseins and β-carotene

Area of Science:

• Food Science and Technology
• Biochemistry
• Molecular Biophysics

Background:

• Beta-carotene (β-carotene) is naturally present in bovine milk.
• Milk proteins, especially casein, play a key role in the stability and properties of low-fat and fat-free dairy products.
• Understanding β-carotene-casein interactions is vital for dairy product formulation and nutritional value.

Purpose of the Study:

• To investigate the molecular interactions between β-carotene and casein in bovine milk.
• To determine the binding characteristics, stoichiometry, and thermodynamic parameters of the interaction.
• To elucidate the effect of this interaction on casein conformation.

Main Methods:

• Spectroscopic techniques: Fluorescence spectroscopy, UV-Vis absorption spectroscopy.
• Circular Dichroism (CD) spectroscopy to analyze protein conformational changes.
• Computer-aided molecular modeling, including docking studies.

Main Results:

• Casein and its fractions bind to β-carotene with a binding constant of approximately 10^4 M^-1 and a 1:1 stoichiometry.
• The interaction is favored under alkaline pH, low ionic strength, and low temperatures.
• Kappa-casein (κ-casein) exhibited the highest binding affinity for β-carotene.
• Van der Waals interactions are the predominant forces driving the binding, confirmed by thermodynamic data and docking.
• Casein conformation was altered: β-casein became more folded, while α- and κ-casein adopted looser structures.

Conclusions:

• Casein effectively binds β-carotene, with κ-casein showing the strongest affinity.
• The binding process is thermodynamically favorable and driven by Van der Waals forces.
• The interaction significantly alters casein secondary and tertiary structures, impacting protein functionality in dairy systems.