Polyoxometalate Binding to Human Serum Albumin: A Thermodynamic and Spectroscopic Approach

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• 作者：Guangjin Zhang ; Bineta Keita ; Constantin T. Craescu ; Simona Miron ; Pedro de Oliveira ; Louis Nadjo
• 刊名：Journal of Physical Chemistry B
• 出版年：2007
• 出版时间：September 27, 2007
• 年：2007
• 卷：111
• 期：38
• 页码：11253 - 11259
• 全文大小：420K
• 年卷期：v.111,no.38(September 27, 2007)
• ISSN：1520-5207

文摘

The molecular recognition of polyoxometalates by human serum albumin is studied using two differentpolyoxometalates (POMs) at pH 7.5. The results are compared with those obtained at pH 3.5 and 9.0. At pH7.5, both POMs strongly interact with the protein with different binding behaviors. The Keggin shaped POM,[H₂W₁₂O₄₀]^6- (H2W12), specifically binds the protein, forming a complex with a 1:1 stoichiometry with K_a= 2.9 × 10⁶ M^-1. The binding constant decreased dramatically with the increase of the ionic strength, thusindicating a mostly electrostatic binding process. Isothermal titration calorimetry (ITC) experiments showthat the binding is an enthalpically driven exothermic process. For the wheel shaped POM [NaP₅W₃₀O₁₁₀]^14-(P5W30), there are up to five binding sites on the protein. Increasing the ionic strength changes the bindingbehavior significantly, leading to a simple exothermic process, with several binding sites. Competitive bindingexperiments indicate that the two POMs share one common binding site. In addition, they show the existenceof another important binding site for P5W30. The two POMs exhibit different binding dependences on thepH. The combination of the experimental results with the knowledge of the surface map of the protein in itsN-B conformation transition domain leads to the proposal for the probable binding site of POMs. The presentwork reveals a protein conformation change upon P5W30 binding, a new feature not explicitly documentedin previous studies.