ZfN: Search Results

1	Author	Jack Farineaua, DanielleM. Laval-, Artinb	Requires cookie*
	Title	Characteristics of Thermoluminescence Bands of Euglena Cells Belonging to 2 Lines Presenting Different Degrees of Diuron-Resistance
	Abstract	We have analysed the thermoluminescence (TL) properties of two lines o f Euglena exhibit ing two degrees of resistance to diuron, by a factor of 100 (Z R 25) and 1000 (Z R 250) respectively, as compared to wild type line (Z). In addition, the two ZR lines developped an identical resistance to atrazine since the I50 for this herbicide in each line was 75 times larger than in wild type. Special TL characteristics were evidenced in the two lines. Bands after 2 flashes (or more) showed a shift o f the peak maximum towards low temperature, the shift being the largest in the most DCM U-resistant cells. Similar results were obtained with isolated thylakoids, except that the TL bands appeared at a temperature higher than in corresponding cells. Oscillations in the amplitude of the bands in a flash sequence were largely damped in cells (and thylakoids), particularly in the most DCM U-resistant lines. The results are interpreted as indicating accumulation of Q a "Qb after flashes due to a decrease of the equilibrium constant for the reaction Q a ~Qb ^ QaQb~ accompanying the D CM U resistance.
	Reference	Z. Naturforsch. 50c, 86—9 (1995); received October 12/November 21 1994
	Published	1995
	Keywords	Diuron, Euglena, Herbicide-Resistance, Photosystem II, Thermoluminescence
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	TEI-XML for	default:Reihe_C/50/ZNC-1995-50c-0086.pdf
	Identifier	ZNC-1995-50c-0086
	Volume	50

2	Author	K. Burda3-, K. Strzałkab, G. H. Schmid3	Requires cookie*
	Title	Europium-and Dysprosium-Ions as Probes for the Study of Calcium Binding Sites in Photosystem II
	Abstract	Trivalent lanthanide cations are suitable probes for C a2+-binding sites in photosystem II (PS II). PS II membranes prepared from Nicoticinci tabacum, intact and depleted of the extrinsic polypeptides were exposed to lanthanide ions (D y3+ and E u 3+). Small concen trations of dysprosium and europium ions enhance oxygen evolution under short saturating flashes. Higher concentrations of the rare earth cations cause the release of the three extrinsic peptides (17, 23 and 33 kDa) and reduce 0 2 yield. The reactivation of the PS II membranes, thus depleted of the 33 kDa subunit, by Ca2+ ions is not possible. Comparing E u 3+ with Dy3+ in this effect shows that E u 3+ is m ore effective than Dy3+, because a lower E u 3+-concentration in comparison to that of Dy3+ inactivates 0 2-evolution. The differences between europium and dysprosium can be explained by their different ionic radius. Our results suggest the existence of two Ca-binding regions: one with a low affinity for calcium would be located on the contact surface of the 23 and 33 kDa proteins and the second one with a high affinity, should be located close to the Mn-cluster and to tyrosine-161 (Z). The more tightly-bound calcium would be responsible for the activity of the PS II system.
	Reference	Z. Naturforsch. 50c, 220 (1995); received O ctober 6/O ctob er 31 1994
	Published	1995
	Keywords	Calcium-Binding Sites, Photosystem II, Tobacco, Oxygen Evolution S-States
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	TEI-XML for	default:Reihe_C/50/ZNC-1995-50c-0220.pdf
	Identifier	ZNC-1995-50c-0220
	Volume	50

3	Author	AchimE G Aua, HubertH. Tholeb, ElfriedeK. Pistoriusa	Requires cookie*
	Title	Isolation and Partial Characterization of a Manganese Requiring L-Arginine Metabolizing Enzyme Being Present in Photosystem II Complexes of Spinach and Tobacco
	Abstract	A low L-arginine metabolizing enzyme (L -A M E) activity leading to ornithine, urea and additional products not identified so far could be detected in photosystem II (PS II) m em branes of spinach and of the chlorophyll deficient tobacco mutant Su/su. The detectable L-AM E activity was very low in untreated PS II membranes, but increased significantly (about 10 fold) when the extrinsic peptides (psbO, P and Q gene products) were removed -suggesting that the L-AM E is exposed at the lumen side o f PS II. It was possible to isolate the detergent-solubilized protein from CaCl2-washed PS II membranes of spinach by a com bination of anion and cation exchange columns. On the basis of SDS PAGE the protein was hom ogenous and had an apparent molecular mass of 7 kDa. N-terminal sequencing of the polypeptide gave a contiguous sequence of 20 amino acids showing no hom ologies to PS II polypeptides as yet sequenced. After chromatography o f the L-AM E on an anion exchange column at pH 9.5 (last purification step) a completely inactive enzyme was obtained. Maximal reactivation was achieved by dialyzing the protein against H epes-N aO H buffer in the pH range of 6.5 to 7.5 containing 100 m M chloride or sulfate (being the most effective anions). The L-AM E activity was totally dependent on manganese added to the reaction mixture. Moreover, there were indications of a second cation binding site being more sequestered and requiring bound Ca2+ or Mn2+ for activity (Sr2+ was less effective and Mg2+ was ineffective). There are indications that the protein contains a redox active group -possibly an amino-acid-derived quinonoid (based on a redox cycling assay with glycine and nitroblue tetrazo-lium). The capability of this PS II associated protein to bind the cofactors of water oxidation and having a redox active group (preliminary results) suggests that this protein might be functional in photosynthetic water oxidation. This is further supported by the fact that the isolated L-AM E has a low catalase activity.
	Reference	Z. Naturforsch. 50c, 638—651 (1995); received May 22/July 10 1995
	Published	1995
	Keywords	L-Arginine Metabolizing Enzyme, Water Oxidizing Enzyme, Photosystem II, Quinoproteins
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	TEI-XML for	default:Reihe_C/50/ZNC-1995-50c-0638.pdf
	Identifier	ZNC-1995-50c-0638
	Volume	50

4	Author	W. I. Gruszecki3, K. Strzałkab, A. R. Adunzc, J. K. Rukb, G. H. Schmidc	Requires cookie*
	Title	Blue Light-Enhanced Photosynthetic Oxygen Evolution from Liposome-Bound Photosystem II Particles; Possible Role of the Xanthophyll Cycle in the Regulation of Cyclic Electron Flow Around Photosystem II?
	Abstract	Light-driven electron transport in liposom e-bound photosystem II (PS-II) particles be tween water and ferricyanide was monitored by bare platinum electrode oxymetry. The m odi fication of the experimental system with the exogenous quinones a-tocopherol quinone (a-TQ) or plastoquinone (PQ) resulted in a pronounced effect on photosynthetic oxygen evolution. The presence o f a-tocopherolquinone (a-T Q) in PS-II samples decreased the rate of red light-induced oxygen evolution but increased the rate o f green light-induced oxygen evolution. Blue light applied to the assay system in which oxygen evolution was saturated by red light resulted in a further increase o f the oxygen signal. These findings are interpreted in terms of a cyclic electron transport around PS-II, regulated by an excitation state of ß-carotene in the reaction centre of PS-II. A mechanism is postulated according to which energetic coupling of ß-carotene in the reaction centre of PS-II and that o f other antenna carotenoid pigments is regulated by the portion of the xanthophyll violaxanthin, which is under control of the xanthophyll cycle.
	Reference	Z. Naturforsch. 50c, 61—6 (1995); received June 15/November 11 1994
	Published	1995
	Keywords	a-Tocopherol Quinone, Plastoquinone-9, Oxygen Evolution, Photosystem II, Cyclic Electron Transport, Xanthophyll Cycle
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	TEI-XML for	default:Reihe_C/50/ZNC-1995-50c-0061.pdf
	Identifier	ZNC-1995-50c-0061
	Volume	50