Solution Speciation of the Dinuclear ZrIV-Substituted Keggin Polyoxometalate [{α-PW11O39Zr(μ-OH)(H2O)}2]8– and Its Reactivity towards DNA-Model Phosphodiester Hydrolysis

The solution speciation of the Zr(IV)-substituted Keggin polyoxometalate (Et2NH2)8[{α-PW11O39Zr(µ-OH)(H2O)}2]•7H2O (ZrK 2:2) was fully determined under different pD, temperature, and concentration conditions. Subsequently, the phosphodiester bond hydrolysis of the DNA model substrate bis-4-nitrophenyl phosphate (BNPP) promoted by ZrK 2:2 was studied in detail. In the presence of ZrK 2:2, phosphoester bond hydrolysis in BNPP proceeded with a rate constant of kobs = 4.75 (± 0.25) × 10-6 s-1 at pD 6.4 and 60 °C, representing a 320-fold rate enhancement in comparison with the spontaneous hydrolysis of BNPP. The pD dependence of kobs exhibits a bell-shaped profile, with the fastest rate observed at pD 6.4. An activation energy (Ea) of 60.16 kJ/mol, enthalpy of activation (∆H#) of 57.44 kJ/mol, entropy of activation (∆S#) of -173.16 J/mol K, and Gibbs activation energy (∆G#) of 111.12 kJ/mol at 37 °C were calculated. The influence of the concentration of ZrK 2:2 on the reaction rate constant was studied in the concentration range 0.5 mM to 6.0 mM. The results showed that ZrK 2:2 is able to hydrolyse an excess of BNPP, demonstrating that ZrK 2:2 acts as a catalyst for phospho(di)ester bond hydrolysis. In addition, the influence of ionic strength and the inhibitor diphenyl phosphate on BNPP hydrolysis were examined.

Publication year:2014

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Authors:International

Authors from:Higher Education

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