Quantitative evaluation of the aqueous dihydronitroxide nitrogen hyperfine coupling constant from QM/MM//MD computations

Houriez, Céline; Ferré, Nicolas; Masella, Michel; Siri, Didier

doi:10.1016/j.theochem.2008.06.010

Cited by 10 publications

(21 citation statements)

References 36 publications

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“…In line with our earlier studies [8,17], we handle the nitrogen out-of-plane displacement by using a harmonic potential U imp = k imp h 2 , where h is the \ONCC improper dihedral angle. We assign k imp together with the parameters of the torsional energy term corresponding to the dihedral angle / ¼ \H b CNC: This allows us to reproduce accurately the quantum PES as a function of (h, /) for the IPENO-OH model nitroxide (see Supporting Information for details).…”

Section: Force Field Parameters and Dmpo-ohmentioning

confidence: 99%

Assessing the accuracy of a QM/MM//MD combined protocol to compute spectromagnetic properties of polyfunctional nitroxides in solution

et al. 2012

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WOS:000305517600003International audienceIn the field of spin trapping chemistry, we proposed a promising new theoretical QM/MM//MD combined protocol to assist the development of new nitrone-based spin traps (Houriez et al. in J Phys Chem B 114:11793-11803, 2010). In the present study, we test its accuracy and its transferability by investigating the spectromagnetic properties in water of DMPO-OH, the nitroxide spin adduct of the 5,5-dimethyl-1-pyrroline-N-oxide nitrone (DMPO) with the OH center dot radical. Thanks to our theoretical method, we obtain quantitative estimates of the DMPO-OH hyperfine coupling constants (hcc's) in very good agreement with experiment. Moreover, our study reveals that the DMPO-OH hcc values are related to the main features of an equilibrium between two major conformations of the nitroxide five-membered ring. Together with our earlier results, the present study clearly establishes the reliability of our theoretical protocol to investigate in condensed phase the behavior of flexible and large nitroxides. Particularly, note that with our method, it is possible to point out clearly fundamental differences in spectromagnetic properties even for two molecules very similar in geometrical structure

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Section: Force Field Parameters and Dmpo-ohmentioning

confidence: 99%

Assessing the accuracy of a QM/MM//MD combined protocol to compute spectromagnetic properties of polyfunctional nitroxides in solution

et al. 2012

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“…Among quantum chemistry methods that treat the interaction between the radical and the environment beyond the continuum model, the QM/MM methods have now received considerable popularity, and several works have recently appeared devoted to QM/MM modeling of electronic g -tensors and hyperfine coupling constants of radicals and other paramagnetic species in solution and protein environments. − Studies, like that of the Cu(II) ion in blue copper proteins, have demonstrated that the QM/MM approach is of superior accuracy for electronic g -tensors compared to QM methods combined with the continuum solvent model. However, QM/MM methods suitable for computation of EPR spin Hamiltonian parameters have so far been limited to rudimentary approaches in which the interaction between the QM and MM regions is described by the QM density interacting with point charges in the MM region ,, or by an approximate electrostatic interaction between fitted multipoles, determined from the QM electron density with “point charges + higher order multipoles” in the MM region .…”

Section: Introductionmentioning

confidence: 99%

Density Functional Theory/Molecular Mechanics Approach for Electronic g-Tensors of Solvated Molecules

et al. 2011

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A general density functional theory/molecular mechanics approach for computation of electronic g-tensors of solvated molecules is presented. We apply the theory to the commonly studied di-tert-butyl nitroxide molecule, the simplest model compound for nitroxide spin labels, and explore the role of an aqueous environment and of various approximations for its treatment. It is found that successive improvements of the solvent shift of the g-tensor are obtained by going from the polarizable continuum model to discrete solvent models of various levels of sophistication. The study shows that an accurate parametrization of the electrostatic potential and polarizability of the solvent molecules in terms of distributed multipole expansions and anisotropic polarizabilities to a large degree relieves the need to explicitly include water molecules in the quantum region, which is the common case in density functional/continuum model approaches. It is also shown that the local dynamics of the solvent around the solute significantly influences the electronic g-tensor and should be included in benchmarking of exchange-correlation functionals for evaluation of solvent shifts of g-tensors. These findings can have important ramifications for the use of advanced hybrid density functional theory/molecular mechanics approaches for modeling spin labels in solvents, proteins, and membrane environments.

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“…Accordingly, such results have to be considered with particular care. [34][35][36] Moreover, because of the molecular size of systems such as DMPO-OOH, their study in solution based on CP MD techniques with long enough simulation times is far from being feasible. During the last years, we devised an alternative strategy based on the combination of classical MD, featuring an ad hoc parametrized polarizable force field, with large scale QM/MM calculations.…”

Section: Introductionmentioning

confidence: 99%

Structure and Spectromagnetic Properties of the Superoxide Radical Adduct of DMPO in Water: Elucidation by Theoretical Investigations

et al. 2010

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In the field of spin trapping chemistry, the design of more efficient radical traps can be assisted by the development of theoretical methods able to give a quantitative evaluation of the electron paramagnetic resonance (EPR) spectrum features of the spin-adduct radical, even before initiating the experimental work. The superoxide radical adduct of the 5,5-dimethyl-1-pyrroline-N-oxide nitrone (DMPO-OOH) has been reported in a huge number of papers devoted to the study of the oxidative stress. Here, we present for the first time the theoretical study of DMPO-OOH in an explicit water solution, based on the combined QM/MM//MD protocol we recently proposed, featuring a full coupling between the solute and all the explicit water molecules. Our results show that the DMPO-OOH EPR spectrum, whose interpretation is still debated, can be explained in the light of two sites in chemical exchange, in agreement with the most recent experimental data. Moreover, we demonstrate that each site consists of an equilibrium between the two main 5-membered ring conformations of DMPO-OOH. We provide also an analysis of the solvent contribution to the hyperfine coupling constants (hcc's) as well as an exhaustive study of the possible relationship between the hcc's and the main structural characteristics of DMPO-OOH. Our QM/MM//MD protocol appears thus to be an accurate theoretical tool allowing the investigation of the magnetic properties of large nitroxide spin adducts in complex environments.

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Quantitative evaluation of the aqueous dihydronitroxide nitrogen hyperfine coupling constant from QM/MM//MD computations

Cited by 10 publications

References 36 publications

Assessing the accuracy of a QM/MM//MD combined protocol to compute spectromagnetic properties of polyfunctional nitroxides in solution

Assessing the accuracy of a QM/MM//MD combined protocol to compute spectromagnetic properties of polyfunctional nitroxides in solution

Density Functional Theory/Molecular Mechanics Approach for Electronic g-Tensors of Solvated Molecules

Structure and Spectromagnetic Properties of the Superoxide Radical Adduct of DMPO in Water: Elucidation by Theoretical Investigations

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