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Solution Speciation of the Dinuclear Zr IV ‐Substituted Keggin Polyoxometalate [{α‐PW 11 O 39 Zr(μ‐OH)(H 2 O)} 2 ] 8– and Its Reactivity towards DNA‐Model Phosphodiester Hydrolysis
Author(s) -
Luong Thi Kim Nga,
Absillis Gregory,
Shestakova Pavletta,
ParacVogt Tatja.
Publication year - 2014
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201402735
Subject(s) - chemistry , phosphodiester bond , polyoxometalate , enthalpy , reaction rate constant , hydrolysis , activation energy , phosphate , catalysis , inorganic chemistry , equilibrium constant , crystallography , entropy of activation , bond energy , medicinal chemistry , stereochemistry , kinetics , molecule , organic chemistry , rna , biochemistry , physics , quantum mechanics , gene
Abstract The solution speciation of the Zr IV ‐substituted Keggin polyoxometalate (Et 2 NH 2 ) 8 [{α‐PW 11 O 39 Zr(μ‐OH)(H 2 O)} 2 ] · 7H 2 O (ZrK 2:2) was fully determined under different pD, temperature, and concentration conditions. Subsequently, 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 k obs = (4.75 ± 0.25) × 10 –6 s –1 at pD 6.4 and 60 °C, which represented a 320‐fold rate enhancement relative to the spontaneous hydrolysis of BNPP. The pD dependence of k obs exhibits a bell‐shaped profile, with the fastest rate observed at pD 6.4. An activation energy ( E a ) of 60.16 kJ mol –1 , enthalpy of activation (Δ H # ) of 57.44 kJ mol –1 , entropy of activation (Δ S # ) of –173.16 J mol –1 K –1 , and Gibbs activation energy (Δ G # ) of 111.12 kJ mol –1 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 to 6.0 m M . The results showed that ZrK 2:2 is able to hydrolyze an excess amount of BNPP, thus 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.