Aquacobalamin (Vitamin B<sub>12</sub><sub>a</sub>) Does Not Bind NO in Aqueous Solution. Nitrite Impurities Account for Observed Reaction

Wolak, Maria; Stochel, Grażyna; Hamza, Mohamed S. A.; Eldik, Rudi van

doi:10.1021/ic991266d

Cited by 71 publications

(80 citation statements)

References 20 publications

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“…[9] NOCbl itself has been associated with considerable controversy in the literature, notwithstanding its existence, [10] and, more recently, whether or not aquacobalamin reacts directly with NO to form NOCbl (it is now generally accepted that this is not the case). [11,12] Indeed, NOCbl was referred to as "elusive" in a recent comprehensive review of vitamin B 12 structures, [13] in which the absence of structural information on NOCbl was noted.…”

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confidence: 99%

“…[13,14] The oxidation state of the Co center of NOCbl is also of considerable interest. [11,12,[15][16][17] Herein, we report the synthesis and X-ray structural characterization of NOCbl, which was prepared by reacting hydroxycobalamin hydrochloride with the NO donor 2-(N,Ndiethylamino)diazenolate-2-oxide (DEA-NONOate) under strictly anaerobic, alkaline conditions (pH 8.9). Isolation of the bulk material by precipitation with acetone gave a bright orange product in 85 % yield that was approximately 97 % pure (see the Supporting Information).…”

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Nitroxylcob(III)alamin: Synthesis and X‐ray Structural Characterization

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Nitroxylcob(III)alamin: Synthesis and X‐ray Structural Characterization

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“…Some authors had interpreted them as the spectrum of NO [11]. However, it was confirmed that those UV-vis spectra were obtained in polar solvents and could be attributed to the formation of HNO 2 [1,12].…”

Section: β-Carotene and Free Radical Reactions With Nitrogen Oxidesmentioning

confidence: 93%

β‐Carotene and Free Radical Reactions with Nitrogen Oxides

Mendiara¹,

Perissinotti²

2017

Carotenoids

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The following presentation is based on experimental work we have already developed and published. We investigated the nitrogen oxides in different solvents and analyzed their reaction with β-carotene. The electron paramagnetic resonance spectroscopy (EPR) and ultraviolet and visible (UV-vis) spectroscopy were applied to investigate the reaction of β-carotene with nitrogen dioxide and nitric oxide in both pure dioxane and dioxane/ water solvent. Free radicals were detected and evaluated with the EPR technique, which is highly selective and sensitive. A reaction mechanism was proposed on the basis of the experimental kinetic and EPR results. The validity of the mechanism was checked by applying simulation set up conditions that reproduced the results achieved. The radical intermediates proposed in the reaction: the β-carotene neutral radicals and the cyclic nitroxide neutral radicals were theoretically studied. For that purpose, the density functional theory (DFT) level was applied, selecting the most suitable method, the unrestricted Becke-style 3-parameter with the Lee-Yang-Parr correlation functional (UB3LYP) and the 6-31G(d) basis sets (d orbital functions). We developed an appropriate discussion on the importance of carotenoids compounds and their reactions in biological media. Also, we evaluated the role and the possible reactions of nitroxide intermediates.

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“…[74] Experimental and theoretical work from our laboratory proved that Cbl(H 2 O) does not react with NO at pH 7. [75,76] Nevertheless, it was reported later that Cbl(H 2 O) reacts with NO at low pH, under conditions in which the dimethylbenzimidazole group is protonated and subsequently dechelates. [77] The final product of this reaction was not a Co III -(NO) complex but Co II -(NO), or better described as Co III -(NO -).…”

Section: Reductive Nitrosylation Of Water-soluble Cobalt Porphyrinsmentioning

confidence: 99%

“…[72c, 75] The reactions of the three complexes under study were strongly pH dependent. At pH Ͼ 3, two reaction steps were clearly observed, whereas at pH Ͻ 3, a single reaction step was observed.…”

Section: Reductive Nitrosylation Of Water-soluble Cobalt Porphyrinsmentioning

confidence: 99%

Mechanistic Studies on the Activation of NO by Iron and Cobalt Complexes

2007

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In this review, the reactions of nitric oxide with selected Fe and Co complexes of biological and environmental importance are reviewed. Fundamental chemical kinetics and mechanisms of reactions that lead to the formation and decay of nitrosyl complexes are illustrated and discussed on the basis of studies on Fe II and the release of NO from metal complexes and on the nature of the stable metal-NO complexes produced in solution.As will be seen for most of the presented reactions, the interaction of NO with the metal complex involves activation of the small NO molecule so that charge transfer occurs as a result of the formation of the metal-NO bond.

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Aquacobalamin (Vitamin B₁₂_a) Does Not Bind NO in Aqueous Solution. Nitrite Impurities Account for Observed Reaction

Cited by 71 publications

References 20 publications

Nitroxylcob(III)alamin: Synthesis and X‐ray Structural Characterization

Nitroxylcob(III)alamin: Synthesis and X‐ray Structural Characterization

β‐Carotene and Free Radical Reactions with Nitrogen Oxides

Mechanistic Studies on the Activation of NO by Iron and Cobalt Complexes

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Aquacobalamin (Vitamin B12a) Does Not Bind NO in Aqueous Solution. Nitrite Impurities Account for Observed Reaction

Cited by 71 publications

References 20 publications

Nitroxylcob(III)alamin: Synthesis and X‐ray Structural Characterization

Nitroxylcob(III)alamin: Synthesis and X‐ray Structural Characterization

β‐Carotene and Free Radical Reactions with Nitrogen Oxides

Mechanistic Studies on the Activation of NO by Iron and Cobalt Complexes

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Product

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Aquacobalamin (Vitamin B₁₂_a) Does Not Bind NO in Aqueous Solution. Nitrite Impurities Account for Observed Reaction