Study on the Interaction of Nd3+ with Human Serum Albumin at Molecular Level

Neodymium is applied widely in agriculture to improve crop nutrition and incidentally in fertilizers, yet little is known of its effect on the biological function of human serum albumin (HSA). The interaction of Nd3+ to HSA 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 HSA by Nd3+ was a static quenching process and the binding constant is 5.71 x 10(4) L mol(-1) and the number of binding sites is 1 at 292 K. The thermodynamic parameters (Delta H-0 = -20.79 kJ mol(-1), Delta G(0) = -26.58 kJ mol(-1), and Delta S-0 = 19.85 J mol(-1) K-1) indicate that electrostatic effect between the protein and Nd3+ is the main binding force. The distance r = 2.91 nm between donor (HSA) and acceptor (Nd3+) was obtained according to Forster's nonradiative energy transfer. In addition, UV-vis, CD and synchronous fluorescence results showed that the addition of Nd3+ changed the conformation of HSA.