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Sneeden, R. P. A.

doi:10.1016/b978-0-12-653850-2.50007-1

Cited by 2 publications

(3 citation statements)

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“…However, the problems attendent to the use of indicators, especially in the presence of reducing agents, has been previously pointed out. 3 In addition as we have shown, only the lower region of the indicator pH range is consistent with the observation of an EPR signal from aquovanadyl ion.…”

Section: Resultssupporting

confidence: 90%

“…In general, the vanadophoric contents are thought to be markedly acidic,7•8,11"13 although this has been disputed. 3•14 The vanadium is usually maintained in the air-sensitive trivalent (V-(III)) state.11•15 Aerobic lysis of the cells produces a deep redbrown mixture, termed the Henze solution. 111617 Vanadophoric vanadium has been shown to have no direct role in plasma oxygen transport,18 but has been implicated for use in discouraging predation4•19 or surface fouling20 by competing organisms.…”

Section: Introductionmentioning

confidence: 99%

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Vanadyl ion EPR as a noninvasive probe of pH in intact vanadocytes from Ascidia ceratodes

Frank¹,

Carlson²

1986

Inorg. Chem.

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Analytical and EPR spectral measurements have been carried out to quantify the nature of sulfate, vanadium, and acidity in the vanadocytes of Ascidia ceratodes. Atomic emission spectroscopic data show that average per cell concentrations of vanadium and sulfur are 0.099 and 0.25 M, respectively. In the cell lysate from 0.85 mL of packed cells, 123.91 pmol of sulfur was found of which only 78.41 pmol precipitated with BaCI,. X-ray fluorescence examination of the BaSO, precipitate showed no evidence of a vanadate contaminant. Extrapolation of vanadium and sulfate quantities to vanadophores yields endogenous concentrations of 1.4 and 1.3 M, respectively. Analytical data for Fe, Zn, Cr, Cu, and P are also reported. EPR spectroscopic examination of whole-cell preparations showed the presence of vanadyl ion, which was quantitated by spectral integration to 13 and 36 mM, respectively, within the vanadophoric cell constituents from two independent collections of animals. The magnetism exhibited by vanirdyl ion within healthy, intact vanadocytes in room-temperature EPR spectra (A, = 1.074 X cm-l, go = 1.968) and frozen-solution spectra (A,l = 1.814 X c d , gl, = 1.935) is shown by comparison with standards to be consistent only with the presence of the free aquo ion. Sources of EPR spectral broadening observed in the vanadocyte frozen-solution spectra ((-7/2)1, line width = 34.0 and 24.3 G in the two collections of animals relative to 12.5 G from 1 mM VOSO, in 100 mM H2S04) were investigated by studying the effect on vanadyl EPR line width of acidity (as H2S04), viscosity, SO:concentration, and high concentrations of the paramagnetic ions VOz+, Coz+, and V3+. Broadening is shown to derive from at least two dimeric vanadyl species, the formation of one of which is enhanced by sulfate but inhibited by chloride or perchlorate. In solutions containing sulfuric acid, the aquovanadyl ion EPR line width is shown to be closely correlated with [H+] over the range 500 mM 2 [H2S04] 1 1 mM. In the presence of 0.5 M v,(sop)3 in 15 mM H2S04, the 31-G V02+ EPR line width was found to accurately reflect the measured pH of 1.9. This line width/pH correlation, exploited to ascertain the internal vanadophoric pH in A. ceratodes vanadocytes, yielded a pH of 1.8 f 0.1. This pH is sufficiently low to prevent hydrolysis of endogenous V(H20)63+ or its autoxidation (E,,,(V3+/V02+) = 283 mV at pH 1.8). The most likely status for V(II1) in vanadocytes at low pH and high [SO:-], keeping in mind previous EXAFS and 'H N M R results, is as the V(S04)(H20)4-5+ complex ion. Finally, a new hypothesis for the utility of V(II1) to tunicates is advanced. Goodbody, I. (26) Tullius, T. D.; Carlson, R. M. K.; Gillum, W. 0.; Frank, P.; Hodgson, K. O., unpublished results. Contribution from theThe decomposition of a-bonded (pyridylmethy1)chromium complexes, 2-and 3-NCSH4CH,CrL, (L = dap (1,3-diaminopropane), dien (diethylenetriamine), trien (triethylenetetramine), and [ 1 5]aneN4 (tetraazacyclopentadecane)), was investigated in aqueous perchloric acid under ae...

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Section: Resultssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Vanadyl ion EPR as a noninvasive probe of pH in intact vanadocytes from Ascidia ceratodes

Frank¹,

Carlson²

1986

Inorg. Chem.

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“…were studied extensively in the Zürich laboratories by Zeiss and co-workers, but this aspect of Zeiss' research is outside the scope of this essay. Some reviews − and two books , provide more details of Zeiss' work in organochromium chemistry.…”

Section: Zeiss At Monsanto: Dayton and Zürich 1955−1975 Focus On Org...mentioning

confidence: 99%

Bis(benzene)chromium. 2. Its Discovery by E. O. Fischer and W. Hafner and Subsequent Work by the Research Groups of E. O. Fischer, H. H. Zeiss, F. Hein, C. Elschenbroich, and Others

Seyferth

2002

Organometallics

123

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Cited by 2 publications

References 360 publications

Vanadyl ion EPR as a noninvasive probe of pH in intact vanadocytes from Ascidia ceratodes

Vanadyl ion EPR as a noninvasive probe of pH in intact vanadocytes from Ascidia ceratodes

Bis(benzene)chromium. 2. Its Discovery by E. O. Fischer and W. Hafner and Subsequent Work by the Research Groups of E. O. Fischer, H. H. Zeiss, F. Hein, C. Elschenbroich, and Others

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