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Title: Interactions of 1-Methylimidazole with UO₂(CH₃CO₂)₂ and UO₂(NO₃)₂: Structural, Spectroscopic, and Theoretical Evidence for Imidazole Binding to the Uranyl Ion

Abstract

The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The first definitive high-resolution single-crystal X-ray structure for the coordination of the 1-methylimidazole (Meimid) ligand to UO₂(Ac)₂ (Ac =CH₃CO₂) is reported. The crystal structure evidence is confirmed by IR, Raman, and UV-vis spectroscopic data. Direct participation of the nitrogen atom of the Meimid ligand in binding to the uranium center is confirmed. Structural analysis at the DFT (B3LYP) level of theory showed a conformational difference of the Meimid ligand in the free gas-phase complex versus the solid state due to small energetic differences and crystal packing effects. Energetic analysis at the MP2 level in the gas phase supported stronger Meimid binding over H₂2O binding to both UO₂(Ac)₂ and UO₂(NO₃)₂. In addition, self-consistent reaction field COSMO calculations were used to assess the aqueous phase energetics of combination and displacement reactions involving H₂O and Meimid ligands to UO₂R₂ (R ) Ac, NO₃). For both UO₂(NO₃)₂ and UO₂(Ac)₂, the displacement of H₂O by Meimid was predicted to be energetically favorable, consistent with experimentalmore » results that suggest Meimid may bind uranyl at physiological pH. Also, log(Knitrate/KAc) calculations supported experimental evidence that the binding stoichiometry of the Meimid ligand is dependent upon the nature of the reactant uranyl complex. These results clearly demonstrate that imidazole binds to uranyl and suggest that binding of histidine residues to uranyl could occur under normal biological conditions.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
921817
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society, 129(3):526-536; Journal Volume: 129; Journal Issue: 3
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ATOMS; CRYSTAL STRUCTURE; HISTIDINE; IMIDAZOLES; NITROGEN; RESIDUES; STOICHIOMETRY; UNIVERSE; URANIUM; Environmental Molecular Sciences Laboratory

Citation Formats

Gutowski, Keith E., Cocalia, Violina A., Griffin, Scott T., Bridges, Nicholas J., Dixon, David A., and Rogers, Robin D. Interactions of 1-Methylimidazole with UO₂(CH₃CO₂)₂ and UO₂(NO₃)₂: Structural, Spectroscopic, and Theoretical Evidence for Imidazole Binding to the Uranyl Ion. United States: N. p., 2007. Web. doi:10.1021/ja064592i.
Gutowski, Keith E., Cocalia, Violina A., Griffin, Scott T., Bridges, Nicholas J., Dixon, David A., & Rogers, Robin D. Interactions of 1-Methylimidazole with UO₂(CH₃CO₂)₂ and UO₂(NO₃)₂: Structural, Spectroscopic, and Theoretical Evidence for Imidazole Binding to the Uranyl Ion. United States. doi:10.1021/ja064592i.
Gutowski, Keith E., Cocalia, Violina A., Griffin, Scott T., Bridges, Nicholas J., Dixon, David A., and Rogers, Robin D. Wed . "Interactions of 1-Methylimidazole with UO₂(CH₃CO₂)₂ and UO₂(NO₃)₂: Structural, Spectroscopic, and Theoretical Evidence for Imidazole Binding to the Uranyl Ion". United States. doi:10.1021/ja064592i.
@article{osti_921817,
title = {Interactions of 1-Methylimidazole with UO₂(CH₃CO₂)₂ and UO₂(NO₃)₂: Structural, Spectroscopic, and Theoretical Evidence for Imidazole Binding to the Uranyl Ion},
author = {Gutowski, Keith E. and Cocalia, Violina A. and Griffin, Scott T. and Bridges, Nicholas J. and Dixon, David A. and Rogers, Robin D.},
abstractNote = {The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The first definitive high-resolution single-crystal X-ray structure for the coordination of the 1-methylimidazole (Meimid) ligand to UO₂(Ac)₂ (Ac =CH₃CO₂) is reported. The crystal structure evidence is confirmed by IR, Raman, and UV-vis spectroscopic data. Direct participation of the nitrogen atom of the Meimid ligand in binding to the uranium center is confirmed. Structural analysis at the DFT (B3LYP) level of theory showed a conformational difference of the Meimid ligand in the free gas-phase complex versus the solid state due to small energetic differences and crystal packing effects. Energetic analysis at the MP2 level in the gas phase supported stronger Meimid binding over H₂2O binding to both UO₂(Ac)₂ and UO₂(NO₃)₂. In addition, self-consistent reaction field COSMO calculations were used to assess the aqueous phase energetics of combination and displacement reactions involving H₂O and Meimid ligands to UO₂R₂ (R ) Ac, NO₃). For both UO₂(NO₃)₂ and UO₂(Ac)₂, the displacement of H₂O by Meimid was predicted to be energetically favorable, consistent with experimental results that suggest Meimid may bind uranyl at physiological pH. Also, log(Knitrate/KAc) calculations supported experimental evidence that the binding stoichiometry of the Meimid ligand is dependent upon the nature of the reactant uranyl complex. These results clearly demonstrate that imidazole binds to uranyl and suggest that binding of histidine residues to uranyl could occur under normal biological conditions.},
doi = {10.1021/ja064592i},
journal = {Journal of the American Chemical Society, 129(3):526-536},
number = 3,
volume = 129,
place = {United States},
year = {Wed Jan 24 00:00:00 EST 2007},
month = {Wed Jan 24 00:00:00 EST 2007}
}
  • The first definitive high-resolution single-crystal X-ray structure for the coordination of the 1-methylimidazole (Meimid) ligand to UO₂(Ac)₂ (Ac ) CH₃CO₂) is reported. The crystal structure evidence is confirmed by IR, Raman, and UV-vis spectroscopic data. Direct participation of the nitrogen atom of the Meimid ligand in binding to the uranium center is confirmed. Structural analysis at the DFT (B3LYP) level of theory showed a conformational difference of the Meimid ligand in the free gas-phase complex versus the solid state due to small energetic differences and crystal packing effects. Energetic analysis at the MP2 level in the gas phase supported strongermore » Meimid binding over H₂O binding to both UO₂(Ac)₂ and UO₂(NO₃)₂. In addition, self-consistent reaction field COSMO calculations were used to assess the aqueous phase energetics of combination and displacement reactions involving H₂O and Meimid ligands to UO₂R₂ (R ) Ac, NO₃). For both UO₂(NO₃)₂ and UO₂(Ac)₂, the displacement of H₂O by Meimid was predicted to be energetically favorable, consistent with experimental results that suggest Meimid may bind uranyl at physiological pH. Also, log(Knitrate/KAc) calculations supported experimental evidence that the binding stoichiometry of the Meimid ligand is dependent upon the nature of the reactant uranyl complex. These results clearly demonstrate that imidazole binds to uranyl and suggest that binding of histidine residues to uranyl could occur under normal biological conditions.« less
  • /sup 15/N, /sup 1/H and /sup 13/C NMR spectra for (/sup 15/N/sub 2/)imidazole and (/sup 15/N/sub 2/)-1-methylimidazole in aqueous solution as functions of pH provide shift and coupling-constant information useful in characterizing the protonated and unprotonated forms of these compounds and as background for determining N binding to other species, such as metal ions. When combined with similar data for the imidazole-ring atoms in histidine, these data give more reliable estimates of tautomeric equilibrium constants for the amphionic and anionic forms of histidine than possible from the histidine data alone.
  • The crystal structure of P450 2B4 bound with 1-(4-chlorophenyl)imidazole (1-CPI) has been determined to delineate the structural basis for the observed differences in binding affinity and thermodynamics relative to 4-(4-chlorophenyl)imidazole (4-CPI). Compared with the previously reported 4-CPI complex, there is a shift in the 1-CPI complex of the protein backbone in helices F and I, repositioning the side chains of Phe-206, Phe-297, and Glu-301, and leading to significant reshaping of the active site. Phe-206 and Phe-297 exchange positions, with Phe-206 becoming a ligand-contact residue, while Glu-301, rather than hydrogen bonding to the ligand, flips away from the active site andmore » interacts with His-172. As a result the active site volume expands from 200 {angstrom}{sup 3} in the 4-CPI complex to 280 {angstrom}{sup 3} in the 1-CPI complex. Based on the two structures, it was predicted that a Phe-206{yields}Ala substitution would alter 1-CPI but not 4-CPI binding. Isothermal titration calorimetry experiments indicated that this substitution had no effect on the thermodynamic signature of 4-CPI binding to 2B4. In contrast, relative to wild-type 1-CPI binding to F206A showed significantly less favorable entropy but more favorable enthalpy. This result is consistent with loss of the aromatic side chain and possible ordering of water molecules, now able to interact with Glu-301 and exposed residues in the I-helix. Hence, thermodynamic measurements support the active site rearrangement observed in the crystal structure of the 1-CPI complex and illustrate the malleability of the active site with the fine-tuning of residue orientations and thermodynamic signatures.« less
  • Ammonia interactions and competition with water at the interface of nanoporous metal organic framework thin films of HKUST-1 (Cu 3Btc 2 , Btc = 1,3,5-benzenedicarboxylate) are investigated with ambient pressure X-ray photoelectron spectroscopy (APXPS). In the absence of water, ammonia adsorption at the Cu 2+ metal center weakens the metal-linker bond of the framework. In the presence of water, due to the higher binding energy (adsorption strength) of ammonia compared to water, ammonia replaces water at the unsaturated Cu 2+ metal centers. The water molecules remaining in the pores are stabilized by hydrogen bonding to ammonia. Hydrogen bonding between themore » water and ammonia strengthens the metal-ammonia interaction due to cooperative interactions. Cooperative interactions result in a reduction in the metal center oxidation state facilitating linker replacement by other species explaining the previously reported structure degradation.« less
  • The dehydration of studtite, [UO 2(2-O 2)(H 2O)2]·2H 2O, to metastudtite, [UO 2(2-O 2)(H 2O) 2], uranyl peroxide minerals that are major oxidative alteration phases of UO2 under conditions of geological storage, has been studied using X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy. XPS of the U 4f region shows small but significant differences between studtite and metastudtite, with the 4f binding energy of studtite the highest reported for a uranyl mineral studied by this technique. Further information on the changes in the electronic structure was elucidated using U M4-edge High Energy Resolution XANES (HR-XANES) spectroscopy, which directly probesmore » f-orbital states. The transition from the 3d to the 5f* orbital is sensitive to variations of the U=Oaxial bond length and to changes in the bond covalency. We report evidences that the covalence in the uranyl fragment decreases upon dehydration. Photoluminescence spectroscopy at near liquid helium temperatures reveals significant spectral differences between the two materials, correlating with the X-ray spectroscopy results. A theoretical investigation has been conducted on the structures of both studtite and metastudtite and benchmarked to the HR-XANES spectra. These illustrate the sensitivity of the 3d to the 5f * transition towards U=Oaxial bond variation.« less