Electron Spin Echo Envelope Modulation Spectroscopy Reveals and Distinguishes Equatorial and Axial Nitrogen Ligands Bound to VO<sup>2+</sup>

LoBrutto, Russell; Hamstra, Brent J.; Colpas, Gerard J.; Pecoraro, Vincent L.; Frasch, Wayne D.

doi:10.1021/ja973517s

Cited by 34 publications

(40 citation statements)

References 23 publications

(62 reference statements)

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“…In agreement with the experiments, all the functionals predict a small value of A N iso and A N z for an axially coordinated nitrogen, like the amino nitrogen in cis-[VO(Hhida) (H 2 O)] [74], but BHandH gives the best results. For this reason, the latter functional is preferred to the others in the application to the models of vanadium proteins.…”

Section: Validation Of the Dft Methodssupporting

confidence: 82%

“…Information on this superhyperfine coupling can be provided by ESEEM spectroscopy, a variant of EPR spectroscopy [62,[69][70][71]. The superhyperfine coupling constants reported for 14 N are in the range 1-8 MHz and vary with the nature, position, and orientation of the ligands [72][73][74]. In studies on the identification of nitrogen donors bound to vanadium in VO 2?…”

Section: Validation Of the Dft Methodsmentioning

confidence: 99%

“…The following VO 2? species, for which ESEEM data are available in the literature, were simulated: [VO(salen)] (4) [72] [74]. We tested several functionals: besides B3LYP, B3PW91, B3P86, and BHandHLYP, also another half-and-half functional BHandH, which is available in Gaussian 03, was used.…”

Section: Validation Of the Dft Methodsmentioning

confidence: 99%

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Application of DFT methods to the study of the coordination environment of the VO2+ ion in V proteins

et al. 2012

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Density functional theory (DFT) methods were used to simulate the environment of vanadium in several V proteins, such as vanadyl-substituted carboxypeptidase (sites A and B), vanadyl-substituted chloroplast F(1)-ATPase (CF(1); site 3), the reduced inactive form of vanadium bromoperoxidase (VBrPO; low- and high-pH sites), and vanadyl-substituted imidazole glycerol phosphate dehydratase (IGPD; sites α, β, and γ). Structural, electron paramagnetic resonance, and electron spin echo envelope modulation parameters were calculated and compared with the experimental values. All the simulations were performed in water within the framework of the polarizable continuum model. The angular dependence of [Formula: see text] and [Formula: see text] on the dihedral angle θ between the V=O and N-C bonds and on the angle φ between the V=O and V-N bonds, where N is the coordinated aromatic nitrogen atom, was also found. From the results it emerges that it is possible to model the active site of a vanadium protein through DFT methods and determine its structure through the comparison between the calculated and experimental spectroscopic parameters. The calculations confirm that the donor sets of sites B and A of vanadyl-substituted carboxypeptidase are [[Formula: see text], H(2)O, H(2)O, H(2)O] and [N(His)(||), N(His)(⊥), [Formula: see text], H(2)O], and that the donor set of site 3 of CF(1)-ATPase is [[Formula: see text], OH(Thr), H(2)O, H(2)O, [Formula: see text]]. For VBrPO, the coordination modes [N(His)(||), N(His)(∠), OH(Ser), H(2)O, H(2)O(ax)] for the low-pH site and [N(His)(||), N(His)(∠), OH(Ser), OH(-), H(2)O(ax)] or [N(His)(||), N(His)(∠), [Formula: see text], H(2)O] for the high-pH site, with an imidazole ring of histidine strongly displaced from the equatorial plane, can be proposed. Finally, for sites α, β, and γ of IGPD, the subsequent deprotonation of one, two, and three imidazole rings of histidine and the participation of a carboxylate group of a glutamate residue ([N(His)(||), [Formula: see text], H(2)O, H(2)O], [N(His)(||), N(His)(||), [Formula: see text], H(2)O], and [N(His)(||), N(His)(||), [Formula: see text], OH(-), [Formula: see text]], respectively) seems to be the most plausible hypothesis.

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Section: Validation Of the Dft Methodssupporting

confidence: 82%

Section: Validation Of the Dft Methodsmentioning

confidence: 99%

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Application of DFT methods to the study of the coordination environment of the VO2+ ion in V proteins

et al. 2012

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“…The apparent inhibitory effect of VO 2ϩ can be abolished by substitution of NH 4 ϩ for K ϩ in the reaction mixture whereas the reaction in the presence of Mg 2ϩ or Mn 2ϩ is not influenced by addition of NH 4 ϩ . Because VO 2ϩ can be coordinated by amines and other nitrogen-donor ligands 3 (41)(42)(43), the high concentration of NH 4 ϩ is likely to cause coordination to VO 2ϩ , converting the system to be equivalent to that in the absence of added divalent metal ion. 4 Table II compares the results of our studies showing the influence of divalent metal ions under single turnover conditions for both intrinsic GTPase and kirromycin-stimulated GTPase activity in the absence of programmed ribosomes.…”

Section: Role Of Mg 2ϩ In Ef-tu Actionmentioning

confidence: 99%

Mg2+ Is Not Catalytically Required in the Intrinsic and Kirromycin-stimulated GTPase Action of Thermus thermophilus EF-Tu

Rütthard

Banerjee

Makinen

2001

Journal of Biological Chemistry

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The influence of divalent metal ions on the intrinsic and kirromycin-stimulated GTPase activity in the absence of programmed ribosomes and on nucleotide binding affinity of elongation factor Tu (EF-Tu) from Thermus thermophilus prepared as the nucleotide-and Mg 2؉ -free protein has been investigated. The GTPase superfamily of proteins, known more commonly as G-proteins, are ubiquitous in cellular systems and serve as key regulatory molecules catalyzing the hydrolysis of the ␤,␥-phosphate bond in GTP (1-4). For most G-proteins this process yields a tightly bound enzyme-product complex requiring the action of a nucleotide exchange factor to kinetically facilitate exchange of the GTP for GDP in the active site. Nucleotide binding and hydrolysis are key to regulating the activity of these enzymes, and both of these steps occur in the presence of the divalent metal ion Mg 2ϩ as the naturally occurring cofactor in the cell. However, in EF-Tu 1 function it has not been possible hitherto to establish whether there is a differential role of the divalent metal ion in nucleotide hydrolysis as opposed to nucleotide binding.In all G-proteins defined hitherto by x-ray crystallographic studies, the substrate analog guanosine 5Ј-(␤,␥-imido)-triphosphate is bound as a complex with Mg 2ϩ in which the divalent metal ion is coordinated to oxygen atoms from the ␤-phosphate and ␥-phosphate groups, and the guanine and divalent metal ion binding sites appear to be tightly coupled (5, 6). For ras (7), for elongation factor Tu from both thermophilic bacteria (8 -11) and Escherichia coli (12, 13), and for G␣-subunits of heterotrimeric G-proteins (14, 15), the dissociation constants for release of protein-bound nucleotide measured in the presence of Mg 2ϩ indicate differential binding affinities for GDP and GTP by at least an order of magnitude. Binding affinities for both nucleotides are often measured kinetically by ligand displacement because G-proteins are less stable when prepared in their nucleotide-free form. Because nucleotide separation is necessary for complete removal of Mg 2ϩ from the protein, the less stable, nucleotide-free form of G-proteins complicates efforts to determine whether the divalent metal ion has differential roles in nucleotide hydrolysis and nucleotide binding.In contrast to the structural instability of elongation factor Tu of mesophiles such as E. coli, the homologous thermostable protein in its nucleotide-free form is less prone to inactivation, and comparison of the kinetics of nucleotide binding shows it to be identical to EF-Tu isolated as the GDP-bound complex from the cytosol (11,16). This characteristic has allowed application of efficient biochemical purification methods for preparation of the nucleotide-free elongation factor from Thermus thermophilus (16,17) and Bacillus stearothermophilus (18, 19) for x-ray structure analysis of the complex formed with an inhibitor analog of GTP in the active site (5, 6). Isolation of nucleotidefree elongation factor Tu (17-20) and p21 ras (7) has also allowed comp...

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“…It has been demonstrated that ESEEM results not only show the presence or absence of nitrogen nuclei coordinated to vanadyl (and possibly the number of the coordinating nitrogen atoms) but also makes it possible to distinguish different types of nitrogen donors based on the empirical correlation between the type of the nitrogen and the 14 N-hyperfine coupling parameters. 28 The application of the ESEEM technique, for example, to vanadyl complexes with ligands, such as hydroxamic acids, 45 N-(2-hydroxyethyl)iminodiacetic acid, 46 4-[2-(salicylidenamino)ethyl]imidazole, 47 N-{2-[(2-pyridylmethylene)amino]phenyl}pyridine-2-carboxamide (Hccapca), 48 and 1,2-bis(2-hydroxybenzamido)benzene (H 4 hybeb) 49 is well documented.…”

Section: Solution Chemistry Of Vanadium and Zinc Complexesmentioning

confidence: 99%

Chemistry and Biochemistry of Insulin-Mimetic Vanadium and Zinc Complexes. Trial for Treatment of Diabetes Mellitus

Sakurai¹,

Katoh²,

Yoshikawa³

2006

Bulletin of the Chemical Society of Japan

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The number of patients suffering from diabetes mellitus (DM), which is a chronic metabolic disorder and mainly classified as either insulin-dependent type 1 or non-insulin-dependent type 2, is increasing throughout the world. The sequence of DM progression makes this disease a major health risk in regard to microvascular disease that leads to kidney failure, blindness, and nerve damage as well as macrovascular disease that leads to amputations, cardiovascular disease, and stroke. To treat DM, several types of insulin preparations and synthetic drugs for type 1 and type 2 DM, respectively, are in clinical use. However, there are several problems concerning the insulin preparations and synthetic drugs, such as physical and mental pain due to daily insulin injections and defects involving several side effects, respectively. Thus, the disease demands extraordinary effects to define pathobiochemical pathways and strategies for prevention and to find new therapeutic approaches. For this purpose, oxovanadium(IV) (vanadyl, VO 2þ ) and zinc(II) containing complexes have been explored as treatments for both types of DM. This article reviews the current state of research on insulin-mimetic and antidiabetic metal complexes, with special focus on paramagnetic vanadyl and diamagnetic zinc(II) complexes with different coordination modes, together with possible reaction mechanisms. New drug delivery systems involving enteric-coated capsulation and a biopolymer are also reviewed.One of the most important findings in the 20th century was that metal ions and their biomolecular complexes are essential for life on the earth and play roles in not only metalloproteins and metalloenzymes but also gene expression.1,2 This fundamental knowledge showed that our health, aging, physiological disorders and diseases are related to the state of the metal ions and their biomolecular complexes in our body. Some clinically useful metal-containing compounds and metal complexes known as metallopharmaceuticals that can regulate human health have been developed to treat or cure many types of diseases. The most distinctive examples are the platinum (Pt) anti-tumor agents, cisplatin and related newly developed Pt complexes, the gold (Au) orally active anti-rheumatoidal agent auronofin, the aluminum (Al) and zinc (Zn) anti-ulcer agents scralfate and polaprezinc, respectively, the selenium (Se) antiinflammatory agent ebselen, and the lithium (Li) anti-manicdepressive agent lithium carbonate.

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Electron Spin Echo Envelope Modulation Spectroscopy Reveals and Distinguishes Equatorial and Axial Nitrogen Ligands Bound to VO²⁺

Cited by 34 publications

References 23 publications

Application of DFT methods to the study of the coordination environment of the VO2+ ion in V proteins

Application of DFT methods to the study of the coordination environment of the VO2+ ion in V proteins

Mg2+ Is Not Catalytically Required in the Intrinsic and Kirromycin-stimulated GTPase Action of Thermus thermophilus EF-Tu

Chemistry and Biochemistry of Insulin-Mimetic Vanadium and Zinc Complexes. Trial for Treatment of Diabetes Mellitus

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Electron Spin Echo Envelope Modulation Spectroscopy Reveals and Distinguishes Equatorial and Axial Nitrogen Ligands Bound to VO2+

Cited by 34 publications

References 23 publications

Application of DFT methods to the study of the coordination environment of the VO2+ ion in V proteins

Application of DFT methods to the study of the coordination environment of the VO2+ ion in V proteins

Mg2+ Is Not Catalytically Required in the Intrinsic and Kirromycin-stimulated GTPase Action of Thermus thermophilus EF-Tu

Chemistry and Biochemistry of Insulin-Mimetic Vanadium and Zinc Complexes. Trial for Treatment of Diabetes Mellitus

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Electron Spin Echo Envelope Modulation Spectroscopy Reveals and Distinguishes Equatorial and Axial Nitrogen Ligands Bound to VO²⁺