Study on the interaction of La3+ with bovine serum albumin at molecular level

The interaction of La3+ to bovine serum albumin (BSA) has been investigated mainly by fluorescence spectra, UV-vis absorption spectra, and circular dichroism (CD) under simulative physiological conditions. Fluorescence data revealed that the quenching mechanism of BSA by La3+ was a static quenching process and the binding constant is 1.75x104 L mol-1 and the number of binding sites is 1 at 289 K. The thermodynamic parameters (ΔH=-20.055 kJ mol-1, ΔG=-23.474 kJ mol-1, and ΔS=11.831 J mol-1 K-1) indicate that electrostatic effect between the protein and the La3+ is the main binding force. In addition, UV-vis, CD, and synchronous fluorescence results showed that the addition of La3+ changed the conformation of BSA. - Highlights: → Fluorescence data was used to demonstrate that BSA fluorescence can be quenched by La3+. → La3+ can bind to BSA with stoichiometric ratio of 1:1. → BSA-La3+ complex is stabilized mainly by electrostatic effect. → Synchronous fluorescence and CD data revealed that BSA undergoes conformational changes upon binding to La3+.