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 ofKwas 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.
Highlights
Phthalocyanines have been one of the most extensively studied classes of organic functional materials because of their aromatic 18-π electron system [8]
The human serum albumin (HSA) solutions were freshly prepared before spectral analysis and the Ni(tspc)4− solutions were protected from direct sunlight and fluorescent light until they were inserted into the cell compartment
The affinity of serum albumin for this phthalocyanine indicates the role of this protein as endogenous carriers of this phthalocyanine as DNA binders
Summary
Phthalocyanines have been one of the most extensively studied classes of organic functional materials because of their aromatic 18-π electron system [8]. They are important blue and green dyes; recently they have been used as photoconducting agents in photocopying machines, as sensing elements in chemical sensors [20,26], electrochromic display devices and photodynamic reagents for cancer therapy and for other medical applications. There have been a number of previous studies on phthalocyanines and metallophthalocyanines as potential microbicides to kill the human immunodeficiency virus [27], the vesicular stomatitis virus [19], bovine viral diarrhea virus [2], pseudorabies virus [2] and herpes simplex virus [25]. Conjugation of sensitizer with biological targeting agents, e.g., monoclonal antibodies or lipoproteins, increases the
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