Ascidia nigra

Certain vertebrates have an astonishing ability to accumulate vanadium in their blood. For example, the ascidian seaworm Phallusia mammilata has a blood concentration of V up to 1900 ppm, which represents more than a millionfold concentration with respect to the sea-water in which it lives. The related organism Ascidia nigra has an even more spectacular accumulation with concentrations up to 1.45% V (i.e. 14 500 ppm) in its blood cells, which also contain considerable concentrations of sulfuric acid (pH 0). One possibility that has been mooted is that the ascidia accumulates vanadate and polyvanadate ions in mistake for phosphate and polyphosphates (p. 528). 

Recently, a reducing blood pigment named tunichrome B-l (10) was isolated from the tunicate Ascidia nigra L. and characterized.351 It has a structure derived from three (3,4,5-trihydroxy)phenylalanine units and the trihydroxyphenyl group is suitable for reducing the metal. 

The ascidians or tunicates (sea squirts) accumulate vanadium from seawater (about 5x 10-8 mol dm-3) to a level of about 1 mol dm-3 and store it in a dilute solution of sulfuric acid (pH<2) in blood cells called vanadocytes. The tunicates thus concentrate vanadium several million-fold. 079 NMR, ESR and EXAFS determinations on whole vanadocyte cells of Ascidia ceratodes and Ascidia nigra indicate that the vanadium is present mainly as aquated V111 probably complexed with sulfate. Some vanadyl ion (5-10%) is also present.1080 1081... 

Fig. 2. Electron micrograph of vanadocytes from Ascidia nigra. Cells were fixed in 2.5% glutaral-dehyde in 0.15 M HC1, followed by 1% osmium tetroxide, pH 7.6. The sections were stained with uranyl acetate N = nucleus, PM = plasmalemma, V = vacuoles (very electron dense presumably because of reduction of osmium tetroxide by V(III).)...

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

Tunicates are the only marine invertebrates in which alkaloid biosynthesis has been extensively investigated (189). In addition to the eudistomins, described below, the tripeptide tunichromes have been investigated, by Nakanishi and coworkers at Columbia University, in the solitary tunicate Ascidia nigra (191) and shermilamine, a benzo-3,6-phenanthroline alkaloid, has been studied in Cystodytes dellechiajei, by Steffan and coworkers at the University of Munich (192). The origin of the (3-carboline ring system of the eudistomins has been studied, by Baker s group at Florida Tech, in Eudistoma olivaceum (193, 194). 

Vanadium is often taken up as vanadate, in a pathway parallel to phosphate. However, its oxidation state within organisms seems to be highly variable. Unusually high concentrations of vanadium occur in certain ascidians (the specific transport behavior of which will be dealt with later). The workers who first characterized the vanadium-containing compound of the tunicate, Ascidia nigra, coined the name tunichrome. The characterization of the compound as a dicatecholate has been reported. 

The levels of vanadium present in some ocean-dwelling asd-dians, such as the sea squirt Ascidia nigra, are extraordinarily high, up to 10 times greater than in the surrounding water. The metal is taken up from seawater (where it is t5q)ically present il.l-1.8 x 10 Ppm) in the form of [VO ] and is stored in vacuoles in specialized blood cells called vanadocytes. 

The levels of vanadium present in some ocean-dwelling ascidians, such as the sea squirt Ascidia nigra, are extraordinarily high, up to 10 times greater than in the... 

Ascaris lumbricoides, 96, 113, 343, 395 Ascidia nigra, 349, 350 Aspergillus oryzae, 268, 269 Asterias forbesii, 112... 

Isol. from the tunicate Ascidia nigra. Blood pigment which selectively accumulates vanadium. rZ-Isomer [97689-87-7]. Tunichrome BI C26H25N3O11 M 555.497 Isol. from A. nigra. Dec. in air on warming. 

Tunichrome a green chromogen in the blood cells of tunicates, e.g. Ascidia nigra, Ciona intestinalis, Molgula manhattensis. 

Actual droplet formation is not necessary as long as the mobile phase can pass through the stationary phase without displacing it. As a matter of fact, both aqueous and nonaqueous biphasic systems have been used (51, 332). Recent results reveal that a variety of natural products such as saponins, saturated fatty acids, and biomacromolecules - the latter on a biphasic aqueous polymer system - can be separated (332). Because of its comparatively rapid and non-destructive action, CPC has recently been used in the isolation of the tunichromes, the rather sensitive phenolic peptides from the vanadium-collecting sea squirt Ascidia nigra (53, 54) and of W-cis- and trans-rciindA from a complex photoisomerization mixture (51). 

Bruening R C, Oltz E M, Furukawa J, Nakanishi K, Kustin K 1985 Isolation and structure of tunichrome B-1, a reducing blood pigment from the tunicate Ascidia nigra L. J Am Chem Soc 107 5298-5300... 

Recently, Bruening etal. (717a) isolated tunichrome B-1 (1036), which is derived from three (3,4,5-trihydroxyphenyl)alanine units, from Ascidia nigra. 

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