Highly efficient immobilization of beta-lactoglobulin in functionalized mesoporous nanoparticles: A simple and useful approach for enhancement of protein stability

The immobilization of β-lactoglobulin-B (BLG-B) onto the amine-functionalized KIT-6 [n-PrNH ₂-KIT-6], which has average pore diameter around 6.5 nm, was studied. [n-PrNH ₂-KIT-6] proved to be highly effective agent for BLG-B adsorption. UV-visible spectroscopy studies demonstrated that the immobilized BLG-B was less prone to thermally induced aggregation than the free protein. Circular dichroism (CD) spectra of free and immobilized BLG-B were recorded and significant differences in both the backbone and aromatic regions of the spectra were observed upon thermic stress. The obtained results showed that structural elements of the immobilized BLG-B are kept strongly together, making the protein more resistant to heat denaturation. The melting temperatures of the free and immobilized BLG-B were measured by far-UV CD, which showed 19 °C higher heat resistance of the immobilized BLG-B compared with its free form. Acrylamide quenching of fluorescence of free and immobilized forms of BLG-B as a function of temperature revealed that the immobilized BLG-B was more resistant to Trp quenching. Therefore immobilization of BLG-B onto [n-PrNH ₂-KIT-6] is accompanied by favorable structural stability of BLG-B in the confined space.