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  • 1
    Electronic Resource
    Electronic Resource
    Release of glucosylglycerol from the cyanobacterium Synechocystis spec. SAG 92.79 by hypoosmotic shock (1990)
    Springer
    Archives of microbiology 153 (1990), S. 405-408 
    Details
    ISSN: 1432-072X
    Keywords: Cyanobacteria ; Exudation ; Salt stress ; Glucosylglycerol ; Synechocystis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When cells of Synechocystis, adapted to 684 mmol/l NaCl, were exposed to hypoosmotic shock by reducing NaCl concentration to more than 250 mmol/l, significant amounts of organic material were liberated which could be increased by increasing shock strength. After maximal hypoosmotic shock (684 mmol/l→ 2 mmol/l NaCl) 40–50% of photosynthetically labelled organic material occurred in the surrounding medium. The main compound exudates was the osmoprotective compound glucosylglycerol. Minor exudates were amino acids, organic acids and carbohydrates. In contrast a hyperosmotic shock (2 mmol/l→684 mmol/l NaCl) liberated only one fourth of the amount liberated by a hypoosmotic shock.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00249013
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  • 2
    Electronic Resource
    Electronic Resource
    Isolation of salt-induced periplasmic proteins from Synechocystis sp. strain PCC 6803 (1999)
    Springer
    Archives of microbiology 171 (1999), S. 214-217 
    Details
    ISSN: 1432-072X
    Keywords: Key words Cyanobacteria ; Periplasmic proteins ; Salt ; adaptation ; Synechocystis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Periplasmic proteins were obtained from control cells and salt-adapted cells of the cyanobacterium Synechocystis sp. PCC 6803 using the method of cold osmotic shock. Two of these proteins (PP 1, apparent mol. mass 27.6 kDa, and PP 3, apparent mol. mass 39.9 kDa) were accumulated in high amounts in the periplasm of salt-adapted cells, while the major periplasmic protein (PP 2, apparent mol. mass 36.0 kDa) was accumulated independently from salt. After isolation from gels and partial sequencing, the proteins could be assigned to proteins deduced from the complete genome sequence of Synechocystis. Neither salt-induced periplasmic proteins (PP 1, Slr0924 and PP 3, Slr1485) exhibited sequence similarity to proteins of known function from databases. The major protein (PP 2-Slr0513) showed significant sequence similarities to iron-binding proteins. All proteins included typical leader sequences at their N-terminus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050702
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  • 3
    Electronic Resource
    Electronic Resource
    Glucosylglycerol-phosphate synthase: target for ion-mediated regulation of osmolyte synthesis in the cyanobacterium Synechocystis sp. strain PCC 6803 (1999)
    Springer
    Archives of microbiology 171 (1999), S. 101-106 
    Details
    ISSN: 1432-072X
    Keywords: Key words Cyanobacteria ; Glucosylglycerol-phosphate ; synthase/phosphatase ; Ions ; Osmolytes ; Salt activation ; Synechocystis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The response of cyanobacteria to a changing osmotic environment includes the accumulation of organic osmolytes such as glucosylglycerol. The activation of the enzymes involved in glucosylglycerol synthesis [glucosylglycerol-phosphate synthase (GGPS) and glucosylglycerol-phosphate phosphatase (GGPP)] in Synechocystis sp. strain PCC 6803 by various salts and salt concentrations was investigated in vitro. GGPS seemed to be the target for salt-mediated regulation of glucosylglycerol synthesis in vitro. GGPS activation was dependent on the concentration of NaCl, and a sigmoidal plot was obtained. Sensitivity to NaCl was markedly enhanced by low Mg+2 concentrations (optimal at 4 mM), but Mg2+ was not absolutely necessary for the Na+ stimulation. As in the case of NaCl, other salts (including MgCl2) stimulated GGPS. The relative order of GGPS activation in the presence of chloride by the cations at constant ionic strength was Li+ 〉 Na+ 〉 K+, Mg2+ Mn2+. No absolute dependence on ionic strength was observed in Mg2+/Na+-exchange experiments. The degree of activation by ions at various concentrations was positively related to the increasing destabilizing properties of the cations according to the Hofmeister rule, where chaotropic cations are most efficient. Cations were responsible for activation since chaotropic anions counteracted the activating effect of cations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050684
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  • 4
    Electronic Resource
    Electronic Resource
    Characterization of a glucosylglycerol-phosphate-accumulating, salt-sensitive mutant of the cyanobacterium Synechocystis sp. strain PCC 6803 (1996)
    Springer
    Archives of microbiology 166 (1996), S. 83-91 
    Details
    ISSN: 1432-072X
    Keywords: Key words Cyanobacteria ; Glucosylglycerol-phosphate ; Osmoprotective compounds ; Random ; cartridge mutagenesis ; Salt adaptation ; StpA protein ; Synechocystis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Salt-sensitive mutants of Synechocystis were obtained by random cartridge mutagenesis, and one mutant (mutant 4) was characterized in detail. The salt tolerance of mutant 4 was reduced to about 20% of that of the wild-type. This was caused by a defect in the biosynthetic pathway of the osmoprotective compound glucosylglycerol (GG). Salt-treated cells of mutant 4 accumulated the intermediate glucosylglycerol-phosphate (GG-P). Only low levels of phosphate-free GG were detected. The phosphorylated form of GG was not osmoprotective and seemed to be toxic. In vitro enzyme assays revealed that GG-P-phosphatase activity was completely absent in mutant 4, while GG-P-synthase remained unchanged. The integration site of the aphII cartridge in mutant 4 and the corresponding wild-type region was cloned and sequenced. Mutant 4 was complemented to salt resistance after transformation by the cloned wild-type region. The integration of the cartridge led to a deletion of about 1.1 kb of the chromosomal DNA. This affected two of the identified putative protein coding regions, orfII and stpA. The ORFII protein shows a high degree of similarity to the receiver domain of response regulator proteins. Related sequences were not found for StpA. We assume that in mutant 4, regulatory genes necessary for the process of salt adaptation in Synechocystis are impaired.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050360
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  • 5
    Electronic Resource
    Electronic Resource
    Identification of salt-regulated genes in the genome of the cyanobacterium Synechocystis sp. strain PCC 6803 by subtractive RNA hybridization (1999)
    Springer
    Archives of microbiology 172 (1999), S. 377-386 
    Details
    ISSN: 1432-072X
    Keywords: Key words Chaperone ; Cyanobacteria ; groEL ; isiA ; RNA helicase ; Salt stress ; Subtractive RNA ¶hybridization ; Synechocystis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To identify genes transcribed preferentially under salt stress, a subtractive RNA hybridization procedure was applied to the cyanobacterium Synechocystis sp. PCC 6803. The screening of a genomic library led to the identification of several RNA species that were more abundant in salt-stressed cells than in control cells. Salt-dependent transcription of the identified genes was verified in Northern blot experiments. In addition to the previously characterized genes cpn60 (encoding GroEL; a molecular chaperone) and isiA (encoding a chlorophyll-binding protein), genes encoding a protein of unknown function (slr0082) and a putative RNA helicase (slr0083) were identified as salt-regulated genes in Synechocystis. Genes slr0082 and slr0083, located at sites adjacent to each other on the Synechocystis chromosome, were transcribed from separate promoters and showed the most significant induction 1–3 h after salt shock. The salt-regulated promoters of these two genes were mapped. Genes cpn60, slr0082, and slr0083 were also found to be induced by a cold shock. The possible role of the identified gene products for salt adaptation of Synechocystis is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050774
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  • 6
    Electronic Resource
    Electronic Resource
    Polytrifluormethylstyrole, eine polymerklasse mit aussergewöhnlichen optischen eigenschaftenVortrag anläßlich der Tagung der Fachgruppe “Makromolekulare Chemie” der Gesellschaft Deutscher Chemiker über “Synthetische Polymere mit außergewöhnlichen Eigenschaften” in Bad Nauheim am 19. und 20. April 1982Herrn Prof. Dr. Otto Bayer in memoriam gewidmet (1982)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 109 (1982), S. 285-293 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Homopolymers of 2-, 3- and 4-trifluoromethylstyrene, 4-perfluoroisopropylstyrene, 3,5-bis-trifluoromethyl-styrene and a 1 : 1 copolymer of 2,4- and 2,5-bis-trifluoromethyl-styrene have been synthesized and the refractive indices nD, Abbe-numbers νD and glass transition temperatures of the polymers have been determined.With regard to optical applications poly-2-trifluoromethyl-styrene is particularly interesting since its optical properties are in a region of the n-ν-diagram that has not been reached by thermoplastic polymers or inorganic glasses before.The most important mechanical and thermal properties of this polymer are reported. Reactivity ratios of the binary copolymerisation of 2-trifluoromethyl-styrene with styrene, methyl-methacrylate and n-butyl-acrylate are listed as well as optical data and glass transition temperatures of some copolymers of 2-trifluoromethyl-styrene.
    Notes: Homopolymerisate aus 2-, 3- und 4-Trifluormethylstyrol, 4-Perfluorisopropylstyrol, 3,5-Bis-trifluormethylstyrol und ein 1 : 1 Copolymerisat aus 2,4- und 2,5-Bis-trifluormethylstyrol wurden hergestellt und Brechungsindices, Abbe-Zahlen sowie Glasübergangstemperaturen der Polymerisate bestimmt.Von diesen Thermoplasten ist das Poly-2-trifluormethylstyrol im Hinblick auf optische Anwendungen besonders interessant, da es in einem weder von anorganischen Gläsern noch von bekannten thermoplastischen Kunststoffen bisher erreichten Gebiet des n-v-Diagrammes liegt.Die wichtigsten mechanischen und thermischen Eigenschaften dieses Polymeren und die Copolymerisationsparameter für die binäre Copolymerisation von 2-Trifluormethylstyrol mit Styrol, Methylmethacrylat und n-Butylacrylat wurden bestimmt. Optische Daten und Glastemperaturen einiger Copolymerisate des 2-Trifluormethylstyrols werden mitgeteilt.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1982.051090119
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  • 7
    Electronic Resource
    Electronic Resource
    [2π + 2π]-Photocycloadditionen in Tricyclo[3.2.2.02,4]nonadien-Derivaten. Synthese einfach überbrückter Tris-σ-homobenzol-Verbindungen (1974)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 107 (1974), S. 1971-1987 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: [2π+2π]-Photocycloaddition Reactions in Tricyclo[3.2.2.02.4]nonadiene Derivatives. Synthesis of Singly Bridged Tris-σ-homobenzene CompoundsThe direct - not, however the acetone sensitized -excitation (λ 〉 280 nm) of the tricyclo-[3.2.2.02,4]nonadiene diester 6a - c and the bis-trifluoromethyl derivatives 6d, e (Δ 〉 230 nm), resp., yields (60-90%) the pentacycles 7a - e resulting from a [2π + 2π]-cycloaddition reaction. A [2π + 2σ]-addition with participation of the cyclopropane ring (leading to 8a - e) is not observed. With comparable selectivity (〉 90% isolated yield) the [2π + 2π]-cyclisation takes place in the 3-oxa-diester 10 (to 11). The tris-σ-homobenzene compounds 7a - e and 11, resp. are thermally isomerized exclusively in a 2σ → 2π-cleavage to the starting dienes 6a - e and 10, resp. (Ea (7a) = 22 kcal/mole; A = 2.2·1012 S-1-1). As exemplary cases the addition of HCl, CH3OH and H2O to the diester 7a and to the dicarboxylic acid 7g, resp., has been studied; in a rather selective way the adducts 13 and 14 (ratio 9:1) are formed in good yields. With the usual attack upon the nonsubstituted edge of the bishomocyclobutadiene partial structure in 7a being sterically hindered, tetracyanoethylene forms the 1:1 adducts 15 and 16.
    Notes: Die direkte - nicht aber die aceton-sensibilisierte -Lichtanregung (λ 〉 280 nm) der Tricyclo[3.2.2.02,4]nonadien-diester 6a - c bzw. der Bis-trifluormethyl-Derivate 6d,e (λ 〉 230 nm) liefert in 60-80 proz. bzw. 90 proz. Ausbeute die aus einer [2π + 2π]-Cycloaddition resultierenden Pentacyclen 7a - e. Eine [2π + 2σ]-Reaktion unter Beteiligung des Cyclopropanringes (zu 8a - e) ist daneben nicht nachweisbar. Gleichermaßen einheitlich (isolierte Ausbeute 〉 90%) verläuft die [2π + 2π]-Cyclisierung im 3-Oxa-Diester 10 (zu 11). Die Tris-σ-homobenzole 7a - e bzw. 11 werden thermisch ausschließlich unter 2σ → 2π-Spaltung zu den Ausgangsdienen der Photoreaktionen 6a - e bzw. 10 isomerisiert (Ea (7a) = 22 kal/mol; A = 2.2·1012s-1). Am Beispiel des Diesters 7a bzw. der Dicarbonsäure 7g wurde die Addition von HCl und CH3OH bzw. Wasser studiert, wobei selektiv die Addukte 13 und 14 (Verhältnis 9:1) in durchweg guten Ausbeuten gewonnen werden. Bei sterischer Behinderung des üblichen Angriffs auf die unsubstituierte Kante des Bishomocyclobutadien-Partialgerüsts in 7a setzt sich TCÄ zu den 1:1-Addukten 15 und 16 um.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19741070620
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  • 8
    Electronic Resource
    Electronic Resource
    [2π + 2π]-Photocycloadditionen in Bicyclo[2.2.2]octadien-Derivaten (1974)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 107 (1974), S. 1957-1970 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: [2π+2π]-Photocycloaddition Reactions in Bicyclo[2.2.2]octadiene DerivativesAs exemplified by the dieser 14a a [2π + 2π]-photocycloaddition in the bicyclo[2.2.2]octadiene skeleton is possible by direct - not, however, by sensitized - excitation. Besides a small fragmentation to dimethylphthalate (and ethylene) no other phototransformation of 14a takes place. With a half-life of ca. 12 min at 19°C the photoproduct 15a is thermally isomerized back to the diene diester 14a. Via a regiospecific addition of HCl, methanol and water to the tetracycles 15a and 15b (H2O) the epimeric products 18, 19 are isolated in a ratio of ca. 9:1. Their structure is elucidated by oxidation of 18c to 21 and 1H-n.m.r. spectroscopic comparison with the isomeric compounds 20 and 22, resp., synthesized by a different route. Towards bishomodienophilic reagents like tetracyanoethylene and dimethyl acetylenedicarboxylate 15a shows the expected reactivity. The addition proceeds at the nonsubstituted edge of the bishomocyclobutadiene unit yielding 24, and 26.
    Notes: Am Beispiel des Diesters 14a wird gezeigt, daß auch im Bicyclo[2.2.2]octadien-Gerüst durch direkte Lichtanregung -nicht jedoch sensibilisiert - eine [2π + 2π]-Cycloaddition möglich ist. Außer einer geringfügigen Fragmentierung zu Phthalsäure-dimethylester (und Äthylen) findet keine konkurrierende Photoumwandlung von 14a statt. Mit einer Halbwertszeit von ca. 12 min bei 19°C isomerisiert sich das Photoprodukt 15a zurück zum Dien-diester 14a. Bei der regiospezifischen Addition von HCl, Methanol und Wasser an die Tetracyclen 15a, 15b (H2O) werden die Epimeren 18, 19 im Verhältnis von ca. 9:1 isoliert. Deren Struktur ist durch Oxidation von 18c zu 21 sowie 1H-NMR-spektrometrischen Vergleich mit den auf anderem Weg synthetisierten Isomeren 20 und 22 gesichert. Auch gegenüber bishomodienophilen Partnern wie Tetracyanäthylen oder Acetylendicarbonsäure-dimethylester besitzt 15a die erwartete Reaktivitat. Die Addition erfolgt stereospezifisch an die nichtsubstituierte Kante des Bishomocyclobutadienteils zu 24 und 26.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19741070619
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  • 9
    Electronic Resource
    Electronic Resource
    A Vibrational Study of Some 1,2,4-Trioxanes (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 992-999 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The vibrational spectra of some 1,2,4-trioxanes present two characteristic bands at 790 and 880 cm-1. On the basis of 18O-isotopic substitution and comparison with analogous compounds, these bands have been assigned to coupled C—O and O—O stretching modes of the C—O—O element.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710508
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  • 10
    Electronic Resource
    Electronic Resource
    Thermolysis and Chemiluminescence of Monocyclic 1,2,4-Trioxan-5-ones (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1851-1860 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 3,6-substituted 1,2,4-trioxan-5-ones 11-14, on heating to 170-200°, underwent unimolecular thermolysis to generate electronically excited singlet ketones with an efficiency of ca. 0.2%. The chemiluminescence quantum yields (φoSCL) depended on the nature of the 6-substitutents and increased linearly with temperature. The Arrhenius activation energies were obtained by measuring the rate of decay of luminescence and determined as 22.9, 30.4, 35.6, and 34.2 kcal/mol for 11-14, respectively. Step analysis of the chemiluminescence of 14 afforded an average activation energy of 44.3 kcal/mol. This latter result is explicable in terms of two decomposition paths, higher and lower in energy, leading to excited and ‘dark’ products, respectively. The thermolysis of trioxanones 12-14 lacking a H-atom at the 6-position is interpreted as involving successive rupture of the peroxide bond, excision of ketone at the 3-substituted end, and loss of CO2, to finally produce ketone originating from the 6-position (see Scheme 4).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770716
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