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Functionalized quinones as versatile precursors toward the synthesis of bimetallic derivatives
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Isolation of the flagellar swelling and identification of retinal in the phototactic flagellate, Ochromonas danica (Chrysophyceae)
No full textOchromonas danica, a freshwater, planktonic chrysophyte, is capable of sensing the light conditions of its environment. This biflagellate alga has a swelling near the base of the short flagellum and a chloroplastidic stigma in close association with it. A procedure is described for the isolation of this three dimensional flagellar swelling, the presumed photoreceptor. In contrast to an earlier method developed for the isolation of the paraflagellar swelling from Euglena gracilis, the protocol reported here for Ochromonas results in higher yields that should facilitate future biochemical investigations and could open avenues of investigation for the isolation and purification of the presumptive receptor protein. To verify the hypothesis that a rhodopsin-like protein might be present in this alga, we applied a standard extraction procedure successfully used in the identification of retinal. We here report the purification and identification of all-trans retinal in Ochromonas cells by column chromatography, HPLC and GC-MS. Since retinal is the chromophore of rhodopsin-like proteins, this finding may suggest that in these unicellular algae, too, a rhodopsin-like protein could be the photoreceptor pigment
Ultrastructure of the apical zone of Euglena gracilis: photoreceptors and motor apparatus
No full textCo-ordination properties of 1,10-phenanthroline-5,6-dione towards group 4 and 5 metals in low and high oxidation states
No full textThe molecular structure of 1,10-phenanthroline-5,6-dione has been determined by X-ray diffraction analysis. The compound reacts with the tetrachlorides of Group 4 metals affording adducts of general formula [MCl4(C12H6N2O2)] (M=Ti, Zr or Hf) and [(MCl4)(2)(C12H6N2O2)] (M=Ti or Hf), N,N'- and N,N,O,O'-co-ordinated respectively. The compound [HfCl4(C12H6N2O2)] is reactive towards TiCl4 affording the bimetallic compound [Cl4Hf(C12H6N2O2)TiCl4]. The reaction of the dione with bis-cyclopentadienyl derivatives of titanium(II), zirconium(II), [MCp2(CO)(2)], and vanadium(II), VCp2, affords derivatives O, O'-co-ordinated to the MCp2 moiety. By reaction of [TiCp2(C12H6N2O2)] with [TiCp2(CO)(2)] the bimetallic derivative [(TiCp2)(2)(C12H6N2O2)] is obtained, which is suggested to contain two TiCp2 fragments, O,O'- and N, N'-co-ordinated to 1,10-phenanthroline-5,6-dione. The [MCp2(C12H6N2O2)] (M=Ti, Zr or V) derivatives react with M'Cl-4 (M=Ti or Hf) to give [Cp2M(C12H6N2O2)M'Cl-4] bimetallics
A look into the reservoir of Euglena gracilis: SEM investigation of the flagellar apparatus
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IDENTIFICATION OF A RHODOPSIN PHOTORECEPTOR IN EUGLENA-GRACILIS
No full textVisual pigments are a class of receptor proteins that absorb light and trigger sensory signals. Retinal-containing proteins are used in nature as photoreceptors mainly in animals vision. Mammalian rhodopsin is the best studied example of a light sensor which couples photon absorption to a cascade of biochemical reactions amplifying the input signal. A surprising discovery was to find rhodopsin also in Archaebacteria and in unicellular eukaryotes. On the basis of absorption microspectroscopic measurements and of inhibition experiments on pigment biosynthetic pathways, we have recently suggested that a rhodopsin could be the functional receptor of the visual process in Euglena gracilis, a flagellate which can use light directly to promote photosynthetic reactions, or as an incident flux of information to adjust its swimming orientation. We here report purification and identification of all-trans-retinal by column chromatography, HPLC and GC-MS in E. gracilis; these findings indicate with absolute certainty that rhodopsin is the photoreceptor molecule of this microorganism
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