Eu(III) luminescence and tryptophan fluorescence spectroscopy as a tool for understanding interactions between hen egg white lysozyme and metal-substituted Keggin type polyoxometalates.

Eu(III) luminescence and tryptophan fluorescence spectroscopy as a tool for understanding interactions between hen egg white lysozyme and metal-substituted Keggin type polyoxometalates. J Inorg Biochem. 2015 Apr 1; Authors: Goovaerts V, Stroobants K, Absillis G, Parac-Vogt TN Abstract The interaction between the lacunary Keggin K7PW11O39, the Eu(III)-substituted Keggin K4EuPW11O39 (Eu-Keggin) and the Ce(IV)-substituted Keggin [Me2NH2]10[Ce(PW11O39)2] (Ce-Keggin) polyoxometalates (POMs), and the proteins hen egg white lysozyme (HEWL) and the structurally homologous α-lactalbumin (α-LA) was studied by steady state and time-resolved Eu(III) luminescence and tryptophan (Trp) fluorescence spectroscopy. The excitation spectrum of Eu-Keggin at lower concentrations ([Eu-Keggin]<100μM) is dominated by a ligand-to-metal charge transfer band (291nm). For higher concentrations ([Eu-Keggin]>250μM) the (5)L6←(7)F0 transition becomes the most intense peak. In the absence of protein, the number of coordinated water molecules to the Eu(III) centre of Eu-Keggin is 4, indicating a 1:1 Eu(III):POM species. In the presence of phosphate buffer this number linearly decreases from 4 to 2 upon increasing phosphate buffer concentration. Upon addition of HEWL, there are no coordinated water molecules, suggesting interaction between Eu-Keggin and the protein surface. In addition, this interaction results in a more than threefold increase of the hype...
Source: Journal of Inorganic Biochemistry - Category: Biochemistry Authors: Tags: J Inorg Biochem Source Type: research