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  • Polymer and Materials Science  (11)
  • Analytical Chemistry and Spectroscopy  (10)
  • allelochemical  (5)
  • Biochemistry  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 18 (1992), S. 197-207 
    ISSN: 1573-1561
    Keywords: Sorgoleone ; mitochondria ; inhibitor ; allelochemical ; allelopathy ; root exudate ; Sorghum bicolor ; electron transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The aim of this investigation was to determine if sorgoleone (SGL), a hydrophobic compound inSorghum bicolor (L.) Moench root exudate, interferes with mitochondrial functions. Tests were conducted on mitochondria isolated from etiolated soybean [Glycine max (L.) Merr.] and corn (Zea mays L.) seedlings. The data show SGL is a potent inhibitor of state 3 and state 4 respiration rates in both soybean and corn. Using either NADH, succinate, or malate as substrate, the I50 was about 0.5μM SGL for state 3 and 5.0μM for state 4 based on 0.3–0.5 mg mitochondrial protein. Absorption spectra indicate SGL blocks electron transport at theb-c 1 complex. These data show that disruption of mitochondrial function may be a mechanism of SGL-mediated growth inhibition previously reported and demonstrate a probable role of SGL inSorghum allelopathy.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 11 (1985), S. 65-72 
    ISSN: 1573-1561
    Keywords: Bioassay ; Lemna minor ; allelochemical ; allelopathy ; duckweed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Investigations in allelopathy often require the use of a bioassay for evaluating limited quantities of potentially active growth regulators. A bioassay procedure was developed usingL. minor grown in 1.5-ml aliquots of nutrient medium with and without allelochemicals in wells of 24-well tissue culture cluster dishes with loose-fitting lids. Tests using six replications per treatment with several flavonoid compounds and derivatives of coumarin, benzoic acid, and cinnamic acid demonstrated that the bioassay was capable of measuring inhibition at levels of compound ranging from 50 to 1000 μmol. Strongly inhibitory treatments were visible after 1 or 2 days. After 7 days of growth, frond number, growth rate, and dry weight were used to evaluate effects. The bioassay system is relatively simple, very sensitive, reproducible, and can be used for testing small amounts and dilute concentrations of unknowns which have been separated by chromatography.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 18 (1992), S. 1-11 
    ISSN: 1573-1561
    Keywords: Sorgoleone ; phytotoxin ; allelochemical ; allelopathy ; root exudate ; Sorghum bicolor ; Sorghums ; weed inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Root exudates ofSorghum bicolor consist primarily of a dihydroquinone that is quickly oxidized to ap-benzoquinone named sorgoleone. The aim of this investigation was to determine the potential activity of sorgoleone as an inhibitor of weed growth. Bioassays showed 125μM sorgoleone reduced radicle elongation ofEragrostis tef. In liquid culture, 50-μM sorgoleone treatments stunted the growth ofLemna minor. Over a 10-day treatment period, 10μM sorgoleone in the nutrient medium reduced the growth of all weed seedlings tested:Abutilon theophrasti, Datura stramonium, Amaranthus retroflexus, Setaria viridis, Digitaria sanguinalis, andEchinochloa crusgalli. These data show sorgoleone has biological activity at extremely low concentrations, suggesting a strong contribution toSorghum allelopathy.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 19 (1993), S. 559-568 
    ISSN: 1573-1561
    Keywords: Juglone ; allelopathy ; allelochemical ; photosynthesis ; chioroplast ; mitochondria ; Lemna minor ; Glycine max
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The impacts of juglone on plant growth and several other physiological functions were evaluated in this study. Juglone inhibitedLemna minor growth, chlorophyll content, and net photosynthesis at treatments between 10 and 40μM. Soybean leaf disks vacuum infiltrated with as little as 10μM juglone had reduced photosynthesis. Oxygen evolution by chloroplasts isolated fromPisum sativum was inhibited by juglone with an I50 of 2μM. Micromolar treatments of juglone stimulated oxygen uptake in mitochondria isolated fromGlycine max. These data suggest perturbations of chloroplast and mitochondrial functions may contribute to plant growth reductions observed in juglone-mediated allelopathy.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 19 (1993), S. 369-375 
    ISSN: 1573-1561
    Keywords: Sorgoleone ; allelochemical ; allelopathy ; photosynthesis ; chloroplast ; root exudate ; Sorghum bicolor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The aim of this investigation was to determine if sorgoleone (SGL), ap-benzoquinone inSorghum bicolor root exudate, is a photosynthesis inhibitor. Assays usingGlycine max leaf disks showed concentrations as low as 10μM SGL inhibited oxygen evolution more than 50%. Tests conducted on chloroplasts isolated fromPisum sativum showed that SGL is a powerful inhibitor of CO2-dependent oxygen evolution. Using a chloroplast suspension equivalent to 80–100μg chlorophyll, the I50 was approximately 0.2μM SGL. These data indicate inhibition of photosynthesis is part of the explanation for growth reduction caused by this allelochemical.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 25 (1987), S. 426-427 
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 43-45 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The versatility of the quadrupole ion trap as a mass spectrometer in which the mass resolution may be varied over a wide range has been demonstrated. Mass resolution of 0.8 × 107 and 1.2 × 107 have been obtained for ions of m/z 414 and m/z 614, respectively, well in excess of the normal value of 3m, where m is the mass of ion. At the highest mass resolution, peak-widths at half-maximum are but 52 × 10-6 u. While it has been shown previously that enhanced mass reslution in the quadrupole ion trap can be achieved by reduction of the mass scanning rate, the range of mass resolutions reported here were achieved by reducing the mass scanning rate, in stages, by an overall factor of ca 5.5 × 104.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 929-934 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: When the working point of a precursor ion confined within a quadrupole ion trap is moved to the vicinity of a boundary of the stability diagram, fragmentation of the precursor ion can be induced by virtue of energy gained from the radio-frequency trapping field. This behaviour is known as the ‘border effect’. When the isolated precursor ion is subjected to a cooling period of variable duration, in the presence of helium buffer gas and prior to experiencing the ‘border effect’, a high degree of control of the fragmentation pattern is achieved. The cooling period causes decreases in both ion kinetic energy and ion axial excursions. From this preliminary study, it is suggested that the deposition of internal energy during the ‘border effect’ can be varied by changing the duration of the cooling period. In addition to a degree of control of internal energy deposition, the amount of energy which can be deposited in this manner, though unknown, appears to exceed those energy levels achievable with resonance excitation and the ‘border effect’ without collisional cooling, in that an additional fragmentation channel is accessed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Commercial gas chromatography quadrupole ion-trap mass spectrometer (GC/ITMS) instruments have been used in a novel way for the study of negative ions formed from perfluorotributyl-amine and polychlorinated biphenyl compounds. Negative ions, formed during a normal electron impact ionization period in which 70 eV electrons were used, were isolated in an ion trap by the application of a negative DC voltage to the ring electrode that caused all positive ions to be ejected from the ion trap; in the subsequent analytical scan, negatives ions were detected with an electron multiplier biased normally so as to detect positive ions. The major negative-ion species detected from FC-43 were m/z 252 to m/z 633; 34 other negative-ion species were detected also, though in low abundance. The observed negative-ion mass range extended from m/z 252 to m/z 633. The signal-to-noise ratio of negative-ion mass spectra was enhanced by operation of the GC/MS instrument in GC mode and averaging the mass spectra acquired. In an examination of 3 hexachlorobiphenyl compounds, the molecular anion cluster around m/z 360 for the non-ortho-substituted congener 169 was observed with a signal-to-noise ratio of ca. 20 for 90 pg injected on column: the response for congener 169 was greater than that for congener 156 (mono-ortho-substituted) which, in turn, was greater than that for congener 153 (di-ortho-substituted).
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 851-865 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Untreated and fire-retardant-treated white α-cellulose samples were isothermally pyrolyzed in a fluidized bath in a nitrogen environment at 298-360°C. Results were reported in terms of volatilization (based on weight loss-time measurements) and the degradation products (based on gas chromatographic-mass spectrometric analysis). The findings products (based on gas chromatographic-mass spectrometric analysis). The findings on untreated cellulose indicate that: (1) pyrolysis occurs in three distinct phases in the temperature range 276-360°C; (2) there is a single activation energy of 42 kcal/mole over this temperature range; (3) the initial rapid weight loss is not due to the desoprtion of water, but primarily to decomposition of the cellulose; molecules: (4) there is little difference in either the quality or relative quantity of the volatiles generated during the three different phases of pyrolysis. The findings on treated cellulose show that the fire retardant, KHCO3, does not markedly change the types of degradation products having molecular weights below about 110, althought it does change their relative concentrations. Furthermore, the rate of product generation and the quantity of residual char are increased.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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