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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Planta 179 (1989), S. 242-250 
    ISSN: 1432-2048
    Keywords: Carotenoid ; Chloroplast differentiation ; Photosystem II (assembly) ; Pigment-protein complex ; Scenedesmus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Dark-grown cells of mutant C-6D of the green alga Scenedesmus obliquus exhibit a high activity of photosystem I (PSI) but lack activity of photosystem II (PSII). These cells contain only the pigment-protein complex CPI, representing the reaction-center of PSI. Only chlorophyll a and precursors of carotenoids (lycopene, neurosporene, ξ-carotene, β-zeacarotene) could be detected in dark-grown cells by analysis using high-performance liquid chromatography. Activity of PSII and the corresponding pigment-protein complex, CPa, develop immediately upon transfer to light. Light-harvesting complexes and higher molecular forms of PSI are synthesized only in the later stages of light-induced chloroplast differentiation. During illumination the amounts of carotenoid precursors decrease and carotenes, xanthophylls and chlorophylls a and b are formed. β-Carotene and lutein are synthesized without a lag-phase. Their kinetics are similar to those of CPa formation and development of PSII activity. In contrast, all other xanthophylls are synthesized only after a lag-phase of about 30 min. Inhibition of the transformation of precursors into carotenoids by nicotine prevents the light-inducible development of PSII activity and CPa formation. During illumination under anaerobic conditions no xanthophylls are synthesized but high amounts of α- and β-carotene accumulate. Such cells exhibit no PSII activity and show only traces of CPa. After subsequent transfer to aerobic conditions the xanthophylls are synthesized and simultaneously active PSII units are formed. The results prove that carotenoids are essential components for the assembly of active PSII units. Strong evidence is given that lutein is the absolute necessary prerequisite for this process. Whether β-carotene is also an absolute necessary prerequisite for a functioning PSII unit cannot be deduced from our experiments.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2048
    Keywords: Chloroplast differentiation ; Light-harvesting complex I ; Long wavelength antenna ; Photosystem I ; Pigment-protein complex ; Scenedesmus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Dark-grown cells of the pigment mutant C-6D of Scenedesmus obliquus, strain D3 (Gaffron 1939), contain only chlorophyll (Chl) a and carotenoid precursors. In these cells a functioning photosystem I (PSI) of basic structure was characterised by a high PSI activity and a low Chl/P700 ratio. The reaction-center complex of PSI (CPI) was shown to exist in the dark-grown cells. These findings demonstrate that the assembly of the core complex of PSI and its function are independent of the presence of carotenoids. Upon illumination, carotenoids, Ch1 b and additional Chl a were synthesized. Newly formed β-carotene was shown by pigment analysis using high-performance liquid chromatography (HPLC) to be incorporated into CPI. Parallel to this process a shift of the long-wavelength fluorescence emission of PSI from 712–714 to 718–719 nm was observed. In the later stages of chloroplast differentiation, when xanthophylls and Chl b were synthesized, a higher-molecular-weight complex of PSI (CPIa) could be isolated. Pigment analysis demonstrated that CPIa contained xanthophylls and Chl b in addition to Chl a and β-carotene. This indicates the formation of a light-harvesting antenna closely associated with PSI (LHCI). The addition of an LHCI to the reaction-center complex of PSI caused an increase in the absorption cross-section of PSI as shown by action spectroscopy and in-vivo fluorescence measurements. A model demonstrating the changes in the molecular organization of PSI during light-induced carotenoid biosynthesis in mutant C-6D of Scenedesmus obliquus is presented.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 95 (1962), S. 2424-2437 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: α-Acyl-lactame erhält man durch gemischte Claisen-Kondensation, vorzugsweise unter Verwendung von pulverisiertem Kalium als Kondensationsmittel. Mit Hilfe chemischer und optischer Methoden wird die Solvolyse von N-Alkyl-lactamen untersucht. Die Umlagerung von α-Acyl-pyrrolidonen in 3-6% HCl oder H2SO4 enthaltendem Äthanol gelingt nicht, während α-Äthoxalyl-N-methylpiperidon-(2) bei höheren Protonkonzentrationen unter CO2-Eliminierung zu 2-Carbäthoxy-N-methyl-tetrahydropyridin umgelagert wird.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and biological testing of analogues of Met-enkephalin, a recently discovered opioid peptide from mammalian brain, are described. Testing involved determination of affinity constants for an opiate receptor site and of analgesic potency in the tail-flick test in mouse. The effects on opioid activity of modifying various parts of the enkephalin molecule are discussed. Tyr-D-Ala-Gly-MePheMet (O)-olThe ending -ol added to the symbol of an amino acid designates the aminoalcohol obtained by reduction of the α-carboxyl group of the amino acid. (FK 33-824), which was highly active in these tests, was subsequently selected for clinical testing.The use of two complementary models - in vitro binding studies and in vivo test for analgesia - for the assessment of biological activity in the evaluation of analogues is explained.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An N methylated residue at the n - 3 position of the chain was used to reduce the maximum number of H-bonds realizable y some D,L-alternating oligopeptides in β4.4-, ↑↑5.6- and ↑↓5.6-helices and thus increase for the oligopeptides, the relative stability of larger β-helices. With D, L-alternating oligoleucines of the series Boc-Leun-OMe, however, this approach did not produce the helices expected. Although ↑↓7.2-helices with only one free NH per strand would theoretically be possible, the N-methylated oligoleucines formed instead flawed β4.4-helices having three free NH's in CHCl3 as well as in other solvents of low polarity. These observations confirm that the stability of β-helices does not depend only on the number of intra-or interstrand H-bonds, and corroborate the idea that β-helices with large cavities are inherently unstable.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 2285-2310 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Thermal Isomerization of Tricyclo[4.1.0.02,7]hept-1(7)-ene: Formation and Trapping Reactions of 1,2,3-CycloheptatrieneThe reaction of (7-bromotricyclo[4.1.0.02,7]hept-1-yl)trimethylsilane (1d) with potassium fluoride or cesium fluoride in dimethyl sulfoxide led to the formation of tricyclo[4.1.0.02,7]hept-1(7)-ene (2) which, above 80°C, rearranged almost completely to 1,2,3-cycloheptatriene (6). 6, as a short-lived reactive intermediate, afforded cycloaddition products with numerous 1,3-dienes and with some 1,3-dipoles. The primary adduct of 6 with N, α-diphenylnitrone isomerized at room temperature to the bridgehead olefin 41, the structure of which has been established by an x-ray analysis. When 6 was generated via 2 from 1-chlorotricyclo[4.1.0.02,7]heptane (1f) and potassium tert-butoxide in tetrahydrofuran above 30°C, the cyclocumulene 6 even in the presence of anthracene yielded the vinyl ether 8.
    Notes: Die Reaktion von (7-Bromtricyclo[4.1.0.02,7]hept-1-yl)trimethylsilan (1d) mit Kaliumfluorid oder Caesiumfluorid in Dimethylsulfoxid führt zur Bildung von Tricyclo[4.1.0.12,7]hept-1(7)-en (2), das sich oberhalb von 80°C praktisch vollständig in das 1,2,3-Cycloheptatrien (6) umlagert. Als kurzlebige, reaktive Zwischenstufe ergibt 6 mit zahlreichen 1,3-Dienen und mit einigen 1,3-Dipolen Cycloadditionsprodukte. Das Primäraddukt von 6 an N, α-Diphenylnitron isomerisiert bei Raumtemperatur zum Brückenkopfolefin 41, dessen Konstitution durch Röntgenstrukturanalyse gesichert wurde. Erzeugt man 6 über 2 aus 1-Chlortricyclo[4.1.0.02,7]heptan (1f) und Kalium-tert-butylat in Tetrahydrofuran oberhalb von 30°C, so entsteht aus dem Cyclocumulen 6 auch in Gegenwart von Anthracen hauptsächlich der Enolether 8.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 25 (1953), S. 545-546 
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 1767-1785 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Tricyclo[4.1.0.02,7]hept-1(7)-ene as a Reactive Intermediate: Diels-Alder Trapping Reactions and Proof of ExistenceThe reaction of bulky lithium amides or potassium tert-butoxide with 1-chlorotricycloheptane 3a, generated tricyclo[4.1.0.02,7]hept-1(7)-ene (7) as a short-lived intermediate which could be trapped with reactive 1,3-dienes like anthracenes, furans and spiro[2.4]hepta-4,6-diene forming [4.1.1]- and [3.1.1.]propellanes. The existence of 7 as a free intermediate has been established by competition experiments.
    Notes: Die Einwirkung von sperrigen Lithiumamiden oder Kalium-tert-butylat auf das 1-Chlortricyclo-heptan 3a, erzeugte Tricyclo[4.1.0.0.2,7]hept-1(7)-en (7) als kurzlebige Zwischenstufe, die sich mit reaktiven 1,3-Dienen wie Anthracenen, Furanen und Spiro[2.4]hepta-4,6-dien unter Bildung von [4.1.1]- und [3.1.1]Propellanen abfangen ließ. Durch Konkurrenzexperimente wurde nachgewiesen, daß 7 als freies Teilchen auftritt.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 26 (1954), S. 1-1 
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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