Hydrolysis of phosphotriesters promoted by a zinc(II) complex bearing an alcohol pendant

Kady, Ismail O.; Tan, Biao; Ho, Zhanying; Scarborough, Todd

doi:10.1039/c39950001137

Cited by 38 publications

(20 citation statements)

References 11 publications

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“…It was interesting to note that a sigmoidal rate profile was obtained for both of the cases, suggesting a definite pH dependence on phosphodiester bond cleavage (Figures 6 and 7). Similar profiles have been previously reported in the literature for phosphate ester hydrolysis promoted by Cu 2 , [14] Zn 2 , [15] and Co 3 [16] complexes. As proposed in these reports, a sigmoidal rate profile is indicative of a hydrolytic mechanism, mediated by a metalhydroxy or a metal-alkoxy intermediate, rather than a radicalinduced cleavage.…”

Section: Resultssupporting

confidence: 77%

Nucleobase-Containing Metallated Polymeric Resins as Artificial Phosphodiesterases: Kinetics of Hydrolysis, pH Dependence, and Catalyst Recycling

Srivatsan

Verma

2001

Chem. Eur. J.

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Two metallated polymeric resins that contain the nucleobase adenine have been investigated for their ability to catalyze the hydrolysis of model phosphodiester substrates. These resins behave in a catalytic manner and display classical Michaelis-Menten kinetics. Consequently, parameters such as kobs, Km, Vmax, and kcat were determined for the two resins for both of the substrates. The most attractive feature of our nucleolytic system is its facile reusability that permits catalysis of multiple hydrolytic reactions, after resin recovery and a simple washing step, without significantly compromising the reaction rate. Involvement of a hydrolytic mechanism for phosphodiester cleavage is proposed on the basis of pH versus hydrolytic rate profiles for the two resins. We have also been able to demonstrate temperature-dependence, solvent effects, and inhibitory nature of vanadate ions on the observed rate of hydrolytic reaction aided by the resins. In conclusion, metallated nucleobase resins represent a new class of nucleolytic reagents and these systems have the potential to be further developed for multifarious applications in chemical biology.

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Section: Resultssupporting

confidence: 77%

Nucleobase-Containing Metallated Polymeric Resins as Artificial Phosphodiesterases: Kinetics of Hydrolysis, pH Dependence, and Catalyst Recycling

Srivatsan

Verma

2001

Chem. Eur. J.

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“…Kady et al [31] found that mononuclear Zn II models with N 3 and N 3 O ligands showed k obs values of between 4.5 î 10 À2 and 1.5 î 10 À6 s À1 for diethyl(4-nitrophenyl)phosphate hydrolysis in water. Itoh et al [32] studied the catalytic hydrolysis of 2,4-dinitrophenyl ethylphosphate using mononuclear Cu II complexes with N 3 ligands.…”

Section: Magnetic Propertiesmentioning

confidence: 98%

Pentacoordinate Nickel(II) Complexes Double Bridged by Phosphate Ester or Phosphinate Ligands: Spectroscopic, Structural, Kinetic, and Magnetic Studies

Santana

Garcı́a

Lozano

et al. 2004

Chemistry A European J

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The bis(phosphatediester)-bridged complexes [[Ni([12]aneN(3))(mu-O(2)P(OR)(2))](2)](PF(6))(2) [[12]aneN(3)=Me(3)[12]aneN(3), 2,4,4-trimethyl-1,5,9-triazacyclododec-1-ene; R=Me (1), Bu (2), Ph (3), Ph-4-NO(2) (4); [12]aneN(3)=Me(4)[12]aneN(3), 2,4,4,9-tetramethyl-1,5,9-triazacyclododec-1-ene; R=Me (5), Bu (6), Ph (7), Ph-4-NO(2) (8)] were prepared by hydrolysis of the phosphate triester with the hydroxo complex [[Ni([12]aneN(3))(mu-OH)](2)](PF(6))(2) or by acid-base reaction of the dialkyl or diaryl phosphoric acid and the above hydroxo complex. The acid-base reaction was also used to synthesise the phosphinate-bridged complexes [[Ni([12]aneN(3))(mu-O(2)PR(2))](2)](PF(6))(2) [[12]aneN(3)=Me(3)[12]aneN(3), R=Me (9), Ph (10); [12]aneN(3)=Me(4)[12]aneN(3), R=Me (11), Ph (12)]. The molecular structures of complexes 2, 3 and 12 were established by single crystal X-ray diffraction studies. The eight-membered rings defined by the nickel atoms and the bridging ligands show distorted twist-boat, chair and boat-boat conformations in 2, 3 and 12, respectively. The experimental susceptibility data for compounds 2, 3 and 12 were fitted by least-squares methods to the analytical expression given by Ginsberg. The best fit was obtained with values of J=-0.11 cm(-1), D=-9.5 cm(-1) and g=2.20 for 2; J=-0.97 cm(-1), D=-9.3 cm(-1) and g=2.21 for 3; and J=-0.14 cm(-1), D=-11.9 cm(-1) and g=2.195 for 12. The magnetic-exchange pathways must involve the phosphate/phosphinate bridges, because these favour antiferromagnetic interactions. The observation of a higher exchange parameter for compound 3 is a consequence of a favourable disposition of the O-P-O bridges. The kinetics for the hydrolysis of TNP (tris(4-nitrophenyl)phosphate) with the dinuclear nickel(II) hydroxo complex [[Ni(Me(3)[12]aneN(3))(mu-OH)](2)](PF(6))(2) was studied by UV-visible spectroscopy. The proposed mechanism for TNP-promoted hydrolysis can be described as one-substrate/two-product, and can be fitted to a Michaelis-Menten equation.

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“…All these reactions were investigated in solvents of much higher polarity than ours, and a very high influence of solvent polarity, for example, for the hydrolysis of 6 b, [37,54] was found for them, as it was found here for the hydrolysis of 6 d. Taking this into consideration it must be concluded that the [Tp'ZnÀOH] complexes are indeed powerful nucleophiles. Their hydrolytic activity is surpassed significantly only by that of bifunctional [57] or bimetallic [58] reagents. The reason for their nucleophilic strength must be the fact that the corresponding [Tp' ZnÀOH 2 ] complexes have very low pK a values [44,53] resulting in the existence of [Tp'ZnÀOH] as such under neutral conditions, with their ZnÀOH functions being available without assistance by a base.…”

Section: Measurementsmentioning

confidence: 93%

Evidence for a Trajectory of Hydrolytic Reactions brought about by [L3Zn−OH] Species

et al. 1999

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A kinetic study has been performed on the hydrolytic cleavage of various triorganophosphates PO-(OR) 2 (OR') by three pyrazolylborate ± zinc hydroxide complexes [Tp'Zn À OH] to form [Tp'Zn À OPO(OR) 2 ] and HOR'. The nature of the reactions (first order both in the zinc complex and the phosphate) and the strongly negative activation entropies (À 54 to À 126 J mol) indicate an intimate association of the ZnÀOH and PO functions in the rate-determining step. Some ester cleavages by [Tp'Zn À OH] show the same kinetic pattern and similar activation parameters. The observations are in accord with a four-center arrangement (ZnOPO or ZnOCO) in the activated complex, that is, the hybrid mechanism discussed for zinc enzyme as well as zinc complex catalyzed hydrolyses. A trajectory for reactions passing through this intermediate has been constructed with the Bürgi ± Dunitz structure correlation method, based on the geometries of 30 [Tp'Zn(X)(Y)] species with truly five-coordinate zinc centers. Its first step is the approach of the substrates oxygen atom to the tetrahedral L 3 ZnÀOH species along the axis of a trigonal bipyramid. In the resulting four-center intermediate with five-coordinate zinc a Berry pseudorotation describes the synchronous formation of the Zn À O-(substrate) and breaking of the ZnÀO-(OH) bonds. The concluding step in the coordination sphere of zinc is the expulsion of the former OH oxygen, now part of the substrate, again along the axis of a trigonal bipyramid. This mechanism, which is applicable to phosphate as well as to ester, amide, and carbon dioxide hydrolysis, is in accord with theoretical models of carbonic anhydrase action.

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Hydrolysis of phosphotriesters promoted by a zinc(II) complex bearing an alcohol pendant

Abstract: A polyamine-zinc(ii) complex with an alcohol pendant promotes the hydrolysis of diethyl(4-nitropheny1)phosphate via transfer of the diethylphosphate group to its alkoxy pendant.

Cited by 38 publications

References 11 publications

Nucleobase-Containing Metallated Polymeric Resins as Artificial Phosphodiesterases: Kinetics of Hydrolysis, pH Dependence, and Catalyst Recycling

Nucleobase-Containing Metallated Polymeric Resins as Artificial Phosphodiesterases: Kinetics of Hydrolysis, pH Dependence, and Catalyst Recycling

Pentacoordinate Nickel(II) Complexes Double Bridged by Phosphate Ester or Phosphinate Ligands: Spectroscopic, Structural, Kinetic, and Magnetic Studies

Evidence for a Trajectory of Hydrolytic Reactions brought about by [L3Zn−OH] Species

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