Rare Earth Metal Ions With Serum Albumin Binding Reaction Studies

The study of interaction between metal ions and proteins is a new frontier of chemistry and life science. Serum albumin (SA) is the most abundant protein in blood plasma and serves as a depot protein and transport protein for numerous endogenous and exogenous compounds. Rare earth ions can be used as a kind of effective probe in biomolecular studies, and their biological effects have received increasingly attention nowadays. Rare earth ions and serum albumin have occupied the important role in aspects of chemistry, biology as well as production and daily life. However, the articles on the interaction between them are less and scattered, therefore, this paper systemically studied the interaction between rare earth ions and serum albumin by fluorescence spectroscopy and ultraviolet spectroscopy.In this paper, The fluorescence of trivalent terbium ion (Tb³⁺) enhanced by serum albumin was studied; the conclusions on the binding sites category and the binding number between Tb³⁺ and SA were drawn by using sensitized fluorescence spectroscopy for the first time; and the quenching effect on Tb₂SA sensitized fluorescence by the titration with other rare earth ions was also studied, from which a "tetrad effect" in the coordination between rare earth ions and serum albumin, and the phenomenon that the position of yttrium ion moves forward were found.Then, the conformational change of SA induced by rare earth ions and pHwas studied by synchronous fluorescence spectroscopy for the first time. The results show that the synchronous fluorescence spectra of tryptophan (Trp) residue have blue shift and are quenched in the presence of rare earth ions; while the spectra of tyrosine (Tyr) residue have no obvious shift, and the fluorescence intensity of Tyr residue decreases when the concentration of rare earth ions is lower, however it increases when the rare earth ions concentration becomes higher. Furthermore, the change of Trp, Tyr residue microenvironment and SA conformation induced by rare earth ions and pH was deduced and the functional difference between rare earth ions and pH was discussed.At last, the interaction between actinium element thorium and bovine serum albumin and that of other relative systems were studied; and additional researches about rare earth ions and serum albumin by ultraviolet spectroscopy were made, which reinforce the conclusions drawn through fluorescence spectroscopy.These studies help us to realize the interaction laws between metal ions and biomolecules. It's very important for the further study on the biological effect of rare earth. More over, the study methods and discussion in this article will have some of reference value on other research fields such as Bioinorganic Chemistry, Analytical Chemistry, etc.