Ascidians The Present Stand

HS04 (plT3 = 1.96). The strongly acidic reaction of lysates of the blood cells, already noted by Henze, is thus due to the intracellular sulfuric acid. 

Examples of tunichromes from Ascidia nigra (suborder Phlebobranchia) (left) and Molgula manhattensis (suborder Stolidobranchia) (right). 

Vanadium(III) in Phlebobranchia ascidians with a high acidity in the signet ring cell vacuoles (e.g. Ascidia gemmata) makes up about 98% of the overall vanadium present in blood cells. The V ratio decreases with increasing pH. According to magnetic 

The insets show the first derivatives of the pre-edge feature (left) and the K-edge (dashed lines fit). The bottom trace is the difference between the experimental and the fit. Reproduced from P. Frank et al, Coord. Chem. Rev., 237, 31-39. Copyright (2003), with permission from Elsevier. Right top, absorption spectrum bottom, first derivative. The arrows indicate disulfide, sulfonate and sulfate. The K-edge maxima of the various sulfur oxidation states are marked on the central horizontal line. Reproduced from P. Frank et al., Inorg. Chem. 38, 260-270. Copyright (1999), with permission from the American Chemical Society. 

It appears to be well established by now that the reductant responsible for the conversion of vanadate(V) to oxovanadium(IV) is nicotine adenine dinucleotide phosphate (NADPH), produced in the pentose phosphate pathway.PI Further reduction to in the vacuoles of the vanadocytes of Phlebobranchia ascidians remains elusive. Several reductants have been proposed and shown to be effective in the in vitro and/or in vivo reduction of to V and/or to including tunichromes. Selected investigations of the related redox chemistry of vanadium can be briefly summarised as follows  

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