A study of zinc ions immobilization by β-lactoglobulin
Bogusław Buszewski, Agnieszka Rodzik, Viorica Railean-Plugaru, Myroslav Sprynskyy, Paweł Pomastowski
Colloids and Surfaces A
The aim of the study was to immobilize zinc ions by β-lactoglobulin (βLG) micelles. The investigation focused on physicochemical properties of β-lactoglobulin and zinc-β-lactoglobulin complexes as well as the stability of the obtained complex in synthetic physiological fluids. Kinetic and isothermal studies of zinc ion immobilization by βLG were conducted based on batch sorption approach, while the mechanism of binding zinc ions to βLG was determined and described by application of several kinetic and isotherm models, such as zero order, first and pseudo-first order, intraparticle Weber-Morris diffusion, Langmuir and Freundlich models. The nature of binding/immobilization of zinc ions to βLG was determined with instrumental complementary analysis by using the spectrometric, spectroscopic, microscopic, thermal and X-ray diffraction methods. The results revealed that zinc ion binding to βLG is a heterogeneous process which consists of three main stages: the stage one was associated with rapid sorption of zinc ions on the surface of βLG micelles, while stages two and three resulted from intramolecular diffusion of zinc ions. Moreover, based on instrumental and stability study it was proven that acidic (Glu, Asp) and aromatic (Tyr, Trp, Phe) amino acid groups participate in formation of Zn-βLG complex as a metallocomplex with nutraceutical potential.
Fluorescence, Protein structure, Ligand binding, Biochemistry