Affiliations: Laboratory of Physical Chemistry, Department of Chemistry, Faculty of Science, University of Guilan, Rasht, Iran | Laboratory of Biophysical Chemistry, Chemistry Department, University of Isfahan, Isfahan, Iran
Note: [] Corresponding author: Hamid Dezhampanah, Laboratory of Physical Chemistry, Department of Chemistry, Faculty of Science, University of Guilan, P.O. Box 41335-1914, Rashat 0098, Iran. Tel.: +98 131 32436305; Fax: +98 131 3233262; E-mails: h.dpanah@guilan.ac.ir, h_dpanah@yahoo.com.
Abstract: The thermodynamic of the binding of nickel (II) tetrasulfonated phthalocyanine anion [Ni(tspc)4−], to human serum albumin (HSA) was investigated in 5 mM aqueous phosphate buffer of pH 7.40 at 25°C using optical absorption spectroscopy. The results show that [Ni(tspc)4−] does not have any affinity for aggregation due to increasing of salt concentration and exists as monomers even in homogeneous aqueous solutions of high ionic strengths (more than 2 M NaCl). The binding constant (K) was obtained by analysis of optical absorption spectra of mentioned complex at various HSA concentrations using SQUAD software. The value of K was estimated to be 4.89×105±0.03 (M−1) at 25°C. The thermodynamic parameters were calculated by van't Hoff equation. The enthalpy and entropy changes were 28.08 kJ/mol and 203.09 J/(mol · K) at 25°C, respectively. The results indicate that the binding is mainly entropy driven and the enthalpy is unfavorable for it, the hydrophobic forces thus playing a major role in the binding process.
Keywords: Human serum albumin, nickel (II) tetrasulfonated phthalocyanine, thermodynamic of binding, optical absorption
DOI: 10.3233/SPE-2011-0512
Journal: Spectroscopy, vol. 25, no. 5, pp. 235-242, 2011
