Biological activation of heteropoly complex of molybdotungstosilicate containing lanthanum K10H 3La(SiMo6W5O39)2x26H2O: spectroscopic approach and microcalorimetry.

In this paper, the biological activation of heteropoly complex of molybdotungstosilicate containing lanthanum K(10)H(3)La(SiMo(6)W(5)O(39))(2)x26H(2)O (LaW(5)) was investigated by spectroscopic approach and microcalorimetry under the human physiological conditions. Fluorescence spectroscopy in combination with UV-Vis absorption spectroscopy was employed to investigate the binding of LaW(5) to bovine serum albumin (BSA). In the mechanism discussion, it was proved that the fluorescence quenching of BSA by LaW(5) is a result of the formation of LaW(5)-BSA complex. Binding parameters were determined using the Stern-Volmer equation. The results of thermodynamic parameters G, H, S at different temperatures indicate that van der Waals interactions and hydrogen bonds play a major role for LaW(5)-BSA association. The distance r between donor (BSA) and acceptor (LaW(5)) was obtained according to fluorescence resonance energy transfer. Furthermore, the calorimetric method was used to monitor the biological activity of LaW(5) in Escherichia coli.