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'Quinones' in keywords Facet   section ZfN Section C  [X]
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1998 (1)
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1Author    K. H. GrumbachRequires cookie*
 Title    Interconversion of Carotenoids and Quinones after Onset of Photosynthesis in Chloroplasts of Higher Plants  
 Abstract    The interconversion of carotenoids and quinones was investigated in beech and spinach leaves as well as isolated intact spinach chloroplasts following a dark-light transition. It is shown that isolated intact chloroplasts which are preincubated for 2 h at pH 7.6 in the dark and re­ illuminated with strong white light are capable not only o f deepoxidizing violaxanthin into antheraxanthin and zeaxanthin but simultaneously change the redox state o f the plastoquinone-pool in their thylakoid membrane. At the same time as violaxanthin is deepoxidized plasto-hydroquinone-9 is oxidized to plastoquinone-9. If the light is turned off zeaxanthin is epoxidized into antheraxanthin and violaxanthin but no significant change in the redox state o f the plasto-quinone-pool occurred. It is concluded that the deepoxidation of violaxanthin is connected to the photosynthetic electron transport in that way that an acidification o f the intrathylakoidal compartment by the vectorial release of protons from the water photooxidizing enzyme system and the plastoquinone-pool is required for the activation of the violaxanthin deepoxidase. This may be taken as further evidence that violaxanthin deepoxidase is located at the inner side o f the thylakoid membrane. Additional evidence for this location site is given by the observation that neither deepoxidation of violaxanthin nor photooxidation of plastohydroquinone-9 occurred after onset o f photosyn­ thesis if non cyclic electron transport was inhibited by DCMU. 
  Reference    Z. Naturforsch. 38c, 393 (1983); received March 15 1983 
  Published    1983 
  Keywords    Carotenoids, Photosynthesis, Quinones, Xanthophyll Cycle 
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 TEI-XML for    default:Reihe_C/38/ZNC-1983-38c-0393.pdf 
 Identifier    ZNC-1983-38c-0393 
 Volume    38 
2Author    DaivaA. Bironaitė, N. Arim, K. Čėnas, JuozasJ. Kulys, AlexanderG. Medentsev, VasiliyK. Akimenko, P. A. Karplus, E. F. Pai, G. E. Schulz, EurJ. BiochemRequires cookie*
 Title      
 Abstract    Fully substituted quinones including som e naturally occurring oxyquinones acted as inhibitors o f yeast gluta­ thione reductase (EC 1.6.4.2). They were competitive, mixed or uncompetitive inhibitors for N A D P H , possess­ ing K j in the range o f 1 -2 0 0 |iM and uncompetitive in­ hibitors for glutathione. Rhein (4,5-dioxy-9,10-anthra-quinone-2-carbonic acid) and 9,10-phenanthrenequi-none were the most effective inhibitors. It is concluded that certain quinones can bind to the N A D P(H)-binding site and to the heteroaromatics binding site at the inter­ face domain (o f the enzyme. 
  Reference    Z. Naturforsch. 46c, 966—9 (1991); received March 4/M ay 71991. 178 6 9 3 -7 0 3 1989 
  Published    1991 
  Keywords    Glutathione Reductase, Inhibition, Quinones 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0966_n.pdf 
 Identifier    ZNC-1991-46c-0966_n 
 Volume    46 
3Author    K.H G Rum BachRequires cookie*
 Title    Distribution of Chlorophylls, Carotenoids and Quinones in Chloroplasts of Higher Plants  
 Abstract    Leaves, cotyledons, isolated chloroplasts and subplastid fractions (thylakoids and envelopes) o f radish (Raphanus sativus L. cv. Saxa) and spinach (Spinacia oleracea L. cv. M atador) were assayed for their pigment and quinone content and com position. Virtually all the chlorophylls, carotenoids and quinones were contained in the thylakoids. Envelopes prepared by the method described contained very low amounts o f chlorophyll a and b, violaxanthin and neoxanthin, but no /7-carotene, lutein, zeaxanthin and antheraxanthin. Am ong the quinones trace am ounts o f plastoquinone and a-tocopherol but no plastohydroquinone, a-tocoquinone and phylloquinone were detected. Presented data may be taken as evidence that in vivo the chloroplast envelope is not a location site o f carotenoids and quinones as generally accepted. Possible im plications for the biosyntheses o f quinones and pigments are discussed. 
  Reference    Z. Naturforsch. 38c, 996—1002 (1983); received August 16 1983 
  Published    1983 
  Keywords    Carotenoids, Chlorophylls, Chloroplasts, Envelopes, Quinones, Thylakoids 
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 TEI-XML for    default:Reihe_C/38/ZNC-1983-38c-0996.pdf 
 Identifier    ZNC-1983-38c-0996 
 Volume    38 
4Author    JonathanM. Keske, J.Malcolm Bruce, P. Leslie, D. UttonRequires cookie*
 Title    A New Method of Solvation Analysis: Applications to Quinones  
 Abstract    A new method o f analysis o f the factor contributing to solvation o f small molecules is de­ scribed. A pproxim ations o f the energetic contributions to the entry o f a molecule into water have been derived from partition coefficient data o f solutes and selected derivatives from a multiplicity o f solvents. These include taking separate account energy o f the cost o f introduction o f a molecular cavity in water, the strength o f solute-water dipolar interactions, and the strengths o f hydrogen bond formation with water o f the lone pairs and hydroxylic hydrogens associated with the molecule. In this report the solvation-free energies o f benzoquinone and hydroquinone in water are described. We also consider the solvation o f the sem iquinone anion and show it to be fundamentally different from that o f either the quinone or hydroquinone; this is discussed as a potentiality for selective binding ("solvation") o f quinone, sem iquinone and hydroquinone in sites o f redox catalysis such as those found in the photosynthetic reaction center. 
  Reference    Z. Naturforsch. 45c, 430 (1990); received December 18 1989 
  Published    1990 
  Keywords    Quinone, Ligand Binding, Reaction Centers, Solvation 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0430.pdf 
 Identifier    ZNC-1990-45c-0430 
 Volume    45 
5Author    I. Agalidis, E. Rivasb, F. Reiss-HussonaRequires cookie*
 Title    Characterization of Reaction Center-B875 Complex of Rhodocyclus gelatinosus: Q B Site Properties Derived from Reconstitution Experiments  
 Abstract    Purified reaction center-B875 pigment-protein complex isolated from Rc. gelatinosus (I. Agalidis, E. Rivas, and F. Reiss-Husson, Photosynth. Res. 23, 2 4 9 -2 5 5 (1990)) was further characterized. In the chromatophores, the quinone content was shown to be 6 menaquinones 8 and 16 ubiquinones 8 per reaction center, indicating that the pool contained both quinone types. Besides the primary (M K S) and secondary (U Q X) electron acceptors o f the reaction cen­ ter, the com plex contains residual quinones from the membrane pool (about 3 M K X and 5 U Q 8) probably associated with the phospholipids. Apparent particle weight o f the complex including bound detergent was 520 ± 46 kDa. The secondary quinone Q B was partially removed from the RC by treatment with 2 -3 % octaethyleneglycol dodecyl ether and 3 —4 m M orthophenanthroline. Reconstitution experi­ ments showed that U Q 6, U Q 9 and U Q ,0 could replace Q B but that M K S and M K , could not. It was concluded that Q B site has a clear specificity towards ubiquinone binding. 
  Reference    Z. Naturforsch. 46c, 99—105 (1991); received October 10/November 26 1990 
  Published    1991 
  Keywords    Purple Bacteria, Reaction Center, Secondary Electron Acceptor, Quinones 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0099.pdf 
 Identifier    ZNC-1991-46c-0099 
 Volume    46 
6Author    Krishna Bala, Swati Kolli, Prasanna Tiwari, MohantyRequires cookie*
 Title    Spirulina platensis  
 Abstract    When Spirulina platensis filaments were exposed to 0.75 mW.m_2.s_1 of ultraviolet-B radi­ ation (the ultraviolet-B radiation under clear sky condition is —1.0 mW.m_2.s_1), an inhibi­ tion in photosystem II activity was observed, the inhibition being 90% after 90 min exposure. Upon exposure to ultraviolet-B, the room temperature emission characteristics of Spirulina cells were altered when excited with light primarily absorbed by chlorophyll a or phycobili-somes. When the cells were exposed for 3 h the emission at 685 nm (F685), when excited at 440 nm (primarily chlorophyll a absorption), was enhanced compared to 715 nm (F 715) band of photosystem I suggesting a decrease in energy transfer from photosystem II to photosys­ tem I. Similarly, when the cells were excited at 580 nm (primarily the phycobilisomes), the ratio of emission intensity at 685 nm (F 685) to that of 655 nm (F655) was decreased in the exposed cells. This change in emission characteristics seems to be linked with the uncoupling of the energy transfer from allophycocyanin to chlorophyll a of photosystem II. A small shift in emission peak positions was also indicated when excited either at 440 nm or 580 nm. Analysis of the fast induction of chlorophyll a transients in the presence and absence of 10 jam 3-(3,4-dichlorophenyl)-l,l-dimethylurea (D CM U) indicated that ultraviolet-B expo­ sure initially affects Q A, the primary stable acceptor of photosystem II, and then the plas-toquinone (PQ) pool. Our results on the loss in photosystem Il-catalyzed Hill activity with p-benzoquinone or dichlorobenzoquinone as electron acceptors also supports the contention that ultraviolet-B, even at low dose, initially alters the Q A of photosystem II and subsequently PQ pool. The analysis of functional pool size of Spirulina suggests a substantial decrease in the functional pool size after 2 h UV-B exposure. These results indicate that in Spirulina low intensity of ultraviolet-B initially damages the reaction centre of photosystem II. 
  Reference    Z. Naturforsch. 53c, 369—3 (1998); received December 15 1997 
  Published    1998 
  Keywords    Fluorescence Transients, Photosystem II, Quinones, Spirulina, Ultraviolet-B 
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 TEI-XML for    default:Reihe_C/53/ZNC-1998-53c-0369.pdf 
 Identifier    ZNC-1998-53c-0369 
 Volume    53