EPR Spectroscopic Studies of Lipoxygenases

Gaffney, Betty J.

doi:10.1002/asia.201901461

Cited by 8 publications

(9 citation statements)

References 53 publications

(192 reference statements)

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“…[5][6][7] An enzymatically active diamagnetic ion in the biomolecules is replaced with a paramagnetic ion, or diamagnetic molecules are labeled with a paramagnetic ion to study them by electron paramagnetic resonance (EPR) spectroscopy. [8][9][10][11][12][13][14][15] This provides scope for structural characterization of biomolecules [16][17][18][19][20] and understanding the local environment around the paramagnetic center. [21][22][23][24] In view of this, many biologically important metal ions, such as copper(II), [25][26][27] cobalt (II), [28][29][30][31] iron(III), [32][33][34] manganese(II), [35,36] and other ions, [37][38][39] have been studied by EPR spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Interpretation of EPR and optical spectra of Ni(II) ions in crystalline lattices at ambient temperature

Kathirvelu

2021

Magnetic Reson in Chemistry

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Many biologically important paramagnetic metal ions are characterized by electron paramagnetic resonance (EPR) spectroscopy to use as spin probes to investigate the structure and function of biomolecules. Though nickel(II) ions are an essential trace element and part of many biomolecules, the EPR properties are least understood. Herein, the EPR and optical absorption spectra measured at 300 K for Ni(II) ions diluted in two different diamagnetic hosts are investigated and reported. The EPR spectrum of a polycrystalline Ni/Mg (3-methylpyrazole) 6 (ClO 4 ) 2 [Ni/MMPC] shows two transitions at X-band frequency ($9.5 GHz), suggesting the zero-field splitting parameter (D) is larger than the resonance field of the free electron (H o ). This incomplete and complex spectrum is successfully analyzed to obtain EPR parameters. The EPR spectrum of the polycrystalline Ni/Zn(pyrazole) 6 (NO 3 ) 2 [Ni/ZPN] shows a triplet spectrum indicating D < H o . A detailed analysis of single-crystal EPR data yielded the spin Hamiltonian parameters. The optical absorption spectra are deconvoluted to understand the symmetry of the coordination environment in the complex.

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Section: Introductionmentioning

confidence: 99%

Interpretation of EPR and optical spectra of Ni(II) ions in crystalline lattices at ambient temperature

Kathirvelu

2021

Magnetic Reson in Chemistry

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“…Hamadou et al (2020) studied the influence of physicochemical characteristics of neem seeds in the biodiesel production. Gaffney (2020) studied via EPR spectroscopy the lipoxygenases, an important and abundant component in soybean seeds. Chakraborty and Bhattacharjee (2020) investigated substances in mustard seeds via EPR spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Ferritin and Free Radicals Species in Seeds by Electron Paramagnetic Resonance

Valezi

Mantovani

Constante

et al. 2021

EUR J SUSTAIN DEV RES

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Biodiesel is a relevant source of renewable energy which has received a lot of attention due to the need to create a renewable fuel matrix. An important source of raw material for the biodiesel production is oilseeds. Considering the lack of studies characterizing magnetic species present in seeds, different types of oilseed samples were characterized and compared using X-band Electron Paramagnetic Resonance spectroscopy, at room temperature and 30 K. It was identified the presence of the semiquinone radical in all seed's samples. Besides the free radical resonance, the presence of ferritin was observed, that is an important Fe complex present in seeds and plants, which, although very studied, still lacks a precise description related with its storage and other processes. This study can potentially assist future research about biodiesel and other products that have seeds as raw material.

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“…2,6,10−12 The most widely accepted mechanism involves two states for the iron site: a high-spin ferric hydroxide and a high-spin ferrous aqua complex (Scheme 1a). 2,13 In the initial step of the reaction cycle, the ferric hydroxide converts the pentadiene unit into a pentadienyl radical via an overall H atom abstraction (Scheme 1b).…”

Section: ■ Introductionmentioning

confidence: 99%

“…All novel compounds (1)(2)(3)(4)6) were structurally characterized by X-ray structure analyses. Representative perspective views of the complex cations 1, 2, and 3 are given in Figure 1, including the applied numbering of those atoms relevant to the subsequent discussion.…”

Section: ■ Introductionmentioning

confidence: 99%

“…54 The reason behind this discrepancy could be the slightly longer Fe−N and Fe−O bonds in the rLOX 7,8 and the extensive hydrogen bonding donor network provided by the protein environment around the active site of the enzyme. 2 H Atom Abstractions from O−H Bonds. The functional model character was established by investigating the reactivity of the ferric complex 1 in abstracting H atoms from both O−H and C−H bonds of organic substrates.…”

Section: ■ Introductionmentioning

confidence: 99%

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Combining Structural with Functional Model Properties in Iron Synthetic Analogue Complexes for the Active Site in Rabbit Lipoxygenase

et al. 2021

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Iron complexes that model the structural and functional properties of the active iron site in rabbit lipoxygenase are described. The ligand sphere of the mononuclear pseudo-octahedral cis-(carboxylato)(hydroxo)iron(III) complex, which is completed by a tetraazamacrocyclic ligand, reproduces the first coordination shell of the active site in the enzyme. In addition, two corresponding iron(II) complexes are presented that differ in the coordination of a water molecule. In their structural and electronic properties, both the (hydroxo)iron(III) and the (aqua)iron(II) complex reflect well the only two essential states found in the enzymatic mechanism of peroxidation of polyunsaturated fatty acids. Furthermore, the ferric complex is shown to undergo hydrogen atom abstraction reactions with O−H and C−H bonds of suitable substrates, and the bond dissociation free energy of the coordinated water ligand of the ferrous complex is determined to be 72.4 kcal•mol −1 . Theoretical investigations of the reactivity support a concerted proton-coupled electron transfer mechanism in close analogy to the initial step in the enzymatic mechanism. The propensity of the (hydroxo)iron(III) complex to undergo H atom abstraction reactions is the basis for its catalytic function in the aerobic peroxidation of 2,4,6-tri(tert-butyl)phenol and its role as a radical initiator in the reaction of dihydroanthracene with oxygen.

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EPR Spectroscopic Studies of Lipoxygenases

Cited by 8 publications

References 53 publications

Interpretation of EPR and optical spectra of Ni(II) ions in crystalline lattices at ambient temperature

Interpretation of EPR and optical spectra of Ni(II) ions in crystalline lattices at ambient temperature

Ferritin and Free Radicals Species in Seeds by Electron Paramagnetic Resonance

Combining Structural with Functional Model Properties in Iron Synthetic Analogue Complexes for the Active Site in Rabbit Lipoxygenase

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