Reactivity of tunichromes: reduction of vanadium(V) and vanadium(IV) to vanadium(III) at neutral pH

Ryan, Daniel E.; Ghatlia, Naresh D.; McDermott, Ann E.; Turro, Nicholas J.; Nakanishi, Kōji; Kustin, Kenneth

doi:10.1021/ja00050a056

Cited by 25 publications

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“…568 In the reaction of tunichrome with V(V), the reduction of V(V) to V(IV) readily took place, whereas the reduction to V(III) only happened with difficulty, if at all, under physiological conditions. 540 Details of the ligand oxidation and the metal reduction will vary with the specific catechol, although some generalizations can be made. 568,569 Several intermediates, including semiquinones and quinones, form although in some of these systems it is difficult to determine the location of the unpaired electron.…”

Section: Catechol-based Model Chemistrymentioning

confidence: 99%

“…577 Fundamental studies of the reaction of V(V) with the simple catechols and substituted catechols are crucial for a detailed understanding of this rich redox chemistry 568,570,[578][579][580] and have been reviewed. 246,250,540,581,582 V(V) catechol complexes have been reported in solution 578,579 and in the solid state. 461 Speciation studies have been carried out showing the formation of 1:1 (105), 1:2 (106), and 1:3 (107) species in various protonation states.…”

Section: Catechol-based Model Chemistrymentioning

confidence: 99%

“…553 Model studies on a range of vanadium catechol and catechol-derived complexes show that when V(V) reacts with a catechol, the ligand undergoes oxidation. 246,250,540,581,582 The resulting vanadium catechol complexes contain vanadium in either oxidation states III or IV with the structures shown as in (102)(103)(104). The ligand-metal electron-transfer reaction varies depending on the solvent.…”

Section: Catechol-based Model Chemistrymentioning

confidence: 99%

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The Chemistry and Biochemistry of Vanadium and the Biological Activities Exerted by Vanadium Compounds

et al. 2004

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Section: Catechol-based Model Chemistrymentioning

confidence: 99%

Section: Catechol-based Model Chemistrymentioning

confidence: 99%

Section: Catechol-based Model Chemistrymentioning

confidence: 99%

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The Chemistry and Biochemistry of Vanadium and the Biological Activities Exerted by Vanadium Compounds

et al. 2004

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“…The tunichromes (Pm-1, Pm-2 and Pm-3) have a dipeptide structure incorporating a b(3, 4, 5-trihydroxyphenyl) group (Taylor et al 1997b). These residues are reactive (Ryan et al 1992), affected by pH changes and might be involved in the colour changes, but because purified tunichrome is not presently available for reconstitution experiments, this assignment remains suggestive and not conclusive. Oltz et al (1988) proposed that the function of tunichrome is to form tunicin fibres "analogous to ... the sclerotization of insect cuticle".…”

Section: Discussionmentioning

confidence: 99%

Analysis of the Henze precipitate from the blood cells of the ascidian Phallusia mammillata

Ciancio

Scippa

Nette

et al. 2004

Naturwissenschaften

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The Henze precipitate, a peculiar blue-green microparticulate obtained by lysis of the blood cells of the ascidian Phallusia mammillata (Protochordata), was investigated with atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray microanalysis. The precipitate was collected from the Henze solution, an unstable red-brown product obtained by treating blood with distilled water, whose degradation yields a characteristic blue-green product. The microparticulates measured 50-100 micro m in diameter and appeared irregular in shape. SEM examination showed smooth, roughly round boundaries. The microparticulate surface examined with AFM appeared as an irregular matrix formed by 70-320-nm-wide mammillate composites, including and embedding small (500-800 nm wide) crystal-like multilayered formations. X- ray analysis showed that the elements present in these same precipitates were mainly C, Si, Al and O. The microparticulate composition appeared close to those of natural waxes or lacquers, embedding amorphous silicates and/or other Si-Al components. The unusual occurrence of Si in ascidian blood and its role are discussed.

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“…Tunichromes, which are a class of hydroxy-dopa-containing tripeptides, have been isolated from some ascidian species (74,75,84,85). Because tunichromes contain pyrogallol and cathecol moieties that can have a reducing functionality, it was proposed that tunichromes participate in the reduction of vanadium in ascidians (86). In fact, pyrogallol (a model tunichrome) reduces V IV to V III in tetrahydrofuran (87).…”

Section: Redox Mechanism Of Vanadiummentioning

confidence: 99%

Advances in research on the accumulation, redox behavior, and function of vanadium in ascidians

Michibata

Ueki

2010

BioMolecular Concepts

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The discovery of high levels of vanadium-containing compounds in ascidian blood cells goes back to 1911. Ascidians, which are also known as tunicates or sea squirts, belong to a subphylum of the Chordata, between the vertebrates and invertebrates. This discovery attracted the attention of an interdisciplinary group of chemists, physiologists, and biochemists, in part because of interest in the possible role of vanadium in oxygen transport as a prosthetic group in respiratory pigments, which was later shown not to be such a role, and in part because of the fact that high levels of vanadium were unknown in other organisms. The intracellular concentration of vanadium in some ascidian species can be as high as 350 mm, which is 107 times that in seawater. Vanadium ions, which are thought to be present in the +5 oxidation state in seawater, are reduced to the +3 oxidation state via the +4 oxidation state and are stored in the vacuoles of vanadium-containing cells called vanadocytes, where high levels of protons and sulfate ions are also found. Recently, many proteins and genes that might be involved in the accumulation and reduction of vanadium have been isolated. In this review, we not only trace the history of vanadium research but also describe recent advances in our understanding of the field from several viewpoints: (i) vanadium-accumulating blood cells, (ii) the energetics of vanadium accumulation, (iii) the redox mechanism of vanadium, (iv) the possible role of sulfate, and (v) the physiological roles of vanadium.

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Reactivity of tunichromes: reduction of vanadium(V) and vanadium(IV) to vanadium(III) at neutral pH

Cited by 25 publications

References 0 publications

The Chemistry and Biochemistry of Vanadium and the Biological Activities Exerted by Vanadium Compounds

The Chemistry and Biochemistry of Vanadium and the Biological Activities Exerted by Vanadium Compounds

Analysis of the Henze precipitate from the blood cells of the ascidian Phallusia mammillata

Advances in research on the accumulation, redox behavior, and function of vanadium in ascidians

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