6.1.2. Aqueous V(III) Chemistry 877 6.1.3. Oxidation State of Vanadium in Tunicates 878 6.1.4. Uptake of Vanadate into Tunicates 879 6.1.5. Vanadium Binding Proteins: Vanabins 879 6.1.6. Model Complexes and Their Chemistry 880 6.1.7. Catechol-Based Model Chemistry 880 6.1.8. Vanadium Sulfate Complexes 881 6.2. Fan Worm Pseudopotamilla occelata 883 7. Vanadium Nitrogenase 883 7.1. Nitrogenases 883 7.2. Biochemistry of Nitrogenase 884 7.3. Clusters in Nitrogenase and Model Systems: Structure and Reactivity 885

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The chemistry and biochemistry of vanadium and the biological activities exerted by vanadium compounds.

Vanadium in Biological Systems

Coordination chemistry of vanadium in biological systems

http://staff.ustc.edu.cn/~fhuang/publications/2015/201509.pdf

Vanadium: Global (bio)geochemistry

Vanadium and proteins: Uptake, transport, structure, activity and function

The reported pH values of ascidian blood cells vary considerably. It is likely that one or two of several different types of blood cell must have a highly acidic solution within their vacuoles, in which vanadium ions would be present in a reduced state. Thus, one of the reasons for the variation in reported pH values may be that measurements of pH were made without fractionation of the total population of cells. In the present experiments, the combination of fractionation of whole cells by density-gradient centrifugation, use of a microelectrode that allows measurements of pH under anaerobic conditions, and atomic absorption spectrometry for determinations of vanadium revealed that the contents of signet ring cells, recently identified as vanadocytes, of three ascidian species, Ascidia gemmata, A. ahodori, and A. sydneiensis samea, had low pH values of 2.4, 2.7, and 4.2, respectively. Results obtained by ESR (electron spin resonance) spectrometry confirmed the values of pH obtained with the microelectrode.

Isolation of highly acidic and vanadium-containing blood cells from among several types of blood cell from Ascidiidae species by density-gradient centrifugation

Ascidian blood cells contain a level of vanadium ion much higher than that in seawater. Blood cells are generally classified into six to nine types based on their morphology. On the basis of a Ficoll gradient for cell fractionation, neutron activation analysis of vanadium ion, and ESR spectra of oxovanadium ion in blood cells, the signet ring cells are the most likely “vanadocytes” in Ascidia ahodori. The vanadyl ion (VO2+), detected in high levels in these cells, binds with some low molecular weight substances through their oxygen donors.

Separation of vanadocytes: Determination and characterization of vanadium ion in the separated blood cells of the ascidian, Ascidia ahodori

The amounts of total vanadium and vanadyl (+4) species contained in each blood cell type of ascidians were determined under a nitrogen atmosphere, using a combined approach of cell fractionation and vanadium measurement by ESR spectrometry. The vanadium-containing blood cells, the so-called vanadocytes, were the signet ring cells in Ascidia gemmata as well as A. ahodori and A. sydneiensis samea. Among several types of blood cell, only the vanadocyte contained vanadium in both +3 and +4 oxidation states, with a ratio of 97. 6:2. 4. The oxidation state of vanadium in the vanadocyte remained constant during the process of cell separation. Further, the oxidation state did not change in the presence of air, provided the cell did not suffer damage.

Valency of vanadium in the vanadocytes of Ascidia gemmata separated by density‐gradient centrifugation

Etude du role du tunichrome dans l'accumulation des ions vanadium dans les cellules sanguines de A. s. samea en determinant la fluorescence autonome induite par cette substance au niveau des vanadocytes isoles par centrifugation en gradient de densite de Ficoll

Vanadium-containing blood cells (vanadocytes) show no fluorescence due to the tunichrome in the ascidian, Ascidia sydneiensis samea : Biochemistry

A tunichrome that has been suggested to be involved in the accumulation of vanadium ions in ascidian blood cells produces an autonomous fluorescence upon excitation with blue-violet light. However, we have found that signet ring cells, which contain large amounts of vanadium, do not fluoresce upon such excitation. The strongest fluorescence due to the tunichrome was observed in morula cells, which do not contain vanadium.

Junko Hirata

Papers

Isolation of highly acidic and vanadium-containing blood cells from among several types of blood cell from Ascidiidae species by density-gradient centrifugation

Separation of vanadocytes: Determination and characterization of vanadium ion in the separated blood cells of the ascidian, Ascidia ahodori

Valency of vanadium in the vanadocytes of Ascidia gemmata separated by density‐gradient centrifugation

Vanadium-containing blood cells (vanadocytes) show no fluorescence due to the tunichrome in the ascidian, Ascidia sydneiensis samea : Biochemistry

Autonomous fluorescence of ascidian blood cells with special reference to identification of vanadocytes