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 1.75×104 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.