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  • 1
    Electronic Resource
    Electronic Resource
    The application of ultraviolet microscopy to the distribution of lignin in wood description and validity of the technique (1969)
    Springer
    Wood science and technology 3 (1969), S. 73-92 
    Details
    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Zusammenfassung Es wurde ein Verfahren zur Bestimmung der Ligninverteilung in der Holzzellwand entwickelt, das sich der Ultraviolett-Mikroskopie bedient. Das beschriebene Verfahren beinhaltet einige wichtige Fortschritte genenüber früheren Anwendungen der UV-Mikroskopie beim Studium der Ligninverteilung. Wie für die Elektronenmikroskopie müssen durch Schnitttechnik und Probenpräparation ultradünne Querschnitte der untersuchten Hölzer angefertigt werden. Die Proben werden dann in monochromatischem UV-Licht durchmustert unter Verwendung wendung eines Quarzreflektors. Das mikroskopische Bild wird photographisch festgehalten und das Negativ anschließend einer densiometrischen Analyse unterworfen. Jede Stufe dieses Untersuchungsverfahrens wurde kritisch untersucht, um Gültigkeit und Grenzen des Verfahrens festzulegen. Das Verfahren eignet sich in idealer Weise zur Untersuchung der Herauslösung von Lignin aus der Holzzellwand während des Kochprozesses; es dürfte darüber hinaus andere wichtige Anwendungsmöglichkeiten in der Holzforschung besitzen.
    Notes: Abstract A method has been developed for the determination of lignin distribution in the wood cell wall by ultraviolet microscopy. The method incorporates some important advances on previus applications of UV microscopy to the study of lignin distribution. Ultrathin cross-sections of wood are obtained by the sample preparation and sectioning techniques of electron microscopy. The specimens are examined in monochromatic ultraviolet light using quartz reflection optics. The microscope image is photographically recorded and the negative is subsequently subjected to densitometric analysis. Each stage of the analytical procedure has been critically assessed to determine its validity and limitations. The method is ideally suited to the study of the removal of lignin from the wood cell wall during cooking and possesses other important applications in wood technology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349985
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  • 2
    Electronic Resource
    Electronic Resource
    The distribution of lignin in sprucewood as determined by ultraviolet microscopy (1969)
    Springer
    Wood science and technology 3 (1969), S. 117-138 
    Details
    ISSN: 1432-5225
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Zusammenfassung Die Verteilung des Lignins in Fichtenholz wurde quantitativ durch Untersuchung von 0,5 μm dicken Querschnitten unter dem UV-Mikroskop bestimmt. Die mittlere Ligninkonzentration war in der Mittelschicht etwa doppelt so hoch wie in der Sekundärwand. Die Ligninkonzentration der Mittelschicht war in den an die Tracheiden anstoßenden Zellecken annähernd viermal höher als in der Sekundärwand, wogegen das Volumen der Sekundärwand wesentlich größer war als das der Mittelschicht. Dagegen befand sich beim Frühholz 72% des gesamten Lignins in der Sekundärwand und nur 28% fanden sich in der Mittelschicht selbst und in ihren Zelleckbereichen. Die entsprechenden Werte für Spätholz betragen 82% bzw. 18%. Die Anwendung von schrägen Längsschnitten von 0,1 μm Dicke erlaubte die Auflösung der Mittelschicht. Die Ligninkonzentration in der Mittllamelle war gleich groß wie in der in den Zellzwickeln befindlichen Mittellamelle und der Ligningehalt der Primärwand war etwa doppelt so groß wie derjenige in der Sekundärwand.
    Notes: Abstract The distribution of lignin in black spruce has been determined quantitatively by the study of 0.5 μm transverse sections in a UV microscope. The average lignin concentration in the compound middle lamella was about twice that in the secondary wall. The lignin concentration of the middle lamella at the cell corners of adjacent tracheids was nearly four times that in the secondary wall but the volume of the secondary wall was much greater than the volume of the middle lamella. Thus, for earlywood, 72% of the total lignin was in the secondary wall leaving only 28% in the compound middle lamella and cell corner middle lamella regions. The corresponding values for latewood were 82% and 18% respectively. Use of oblique longitudinal sections of 0.1 μm thick permitted the resolution of the compound middle lamella. The lignin concentration in the true middle lamella was found to be equal to that in the cell corner middle lamella and the primary wall lignin content to be about twice that in the secondary wall.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00639636
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  • 3
    Electronic Resource
    Electronic Resource
    Reactions of wood components with hydrogen sulfide. VIII. Influence of cation and base catalysts on the reductive thiolation reaction at cellulose-reducing endgroupsPresented at the Third Canadian Wood Chemistry Symposium, June 24-26, 1970, Vancouver, B.C. (1971)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 15 (1971), S. 1-9 
    Details
    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: In the presence of calcium, magnesium, and ammonium ions, the reductive thiolation reaction at cellulose-reducing endgroups by a hydrogen sulfide-hydrosulfide ion buffer system is more efficient when compared to the sodium base system. The calcium and magnesium base systems show a maximum reaction rate when the buffer pH is 5.9, thus behaving similarly to the previously described sodium base system. In the ammonium base system, however, there is a specific ammonia-catalyzed reaction with no maximum in the reaction rate over the available pH range. The increased efficiency of the bivalent ion systems is thought to be due to the formation of a salt-like complex between the cation and an intermediate gem-dithiol structure in the reductive thiolation reaction scheme. Ammonia enters into the kinetics of the reaction, but the exact mechanism of its action is unclear. Some other nitrogenous bases also catalyze the reductive thiolation. The use of ammonium hydrosulfide to carry out the reductive thiolation reaction is also briefly described.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1971.070150101
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  • 4
    Electronic Resource
    Electronic Resource
    Observations on the isolation and subfractionation of amylose: The presence in amylose of a natural barrier to β-amylolysisThis is Part XXXI in the Series “Physicochemical Studies on Starches”; Part XXX, Stärke 15 (1963) 444. (1964)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 79 (1964), S. 189-206 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Amylose, die aus Kartoffel-, Weizen- und iris-germanica-Stärke nach den üblichen Methoden isoliert worden war, wurde aus einer Dispersion in Dimethylsulfoxyd durch Zugabe von Äthanol und anderen Fällungsmitteln unterfraktioniert. Es wurden Fraktionen erhalten, deren Viskositätszahl einen weiten Bereich überstreicht und die, was wichtiger ist, in dem bei dem Abbau mit β-Amylase erhaltenen Grenzwert [β] differierten. Nach Ultrazentrifugenmessungen in verdünntem Alkali schienen alle Proben homogen zu sein. Wurden die Ultrazentrifugenmessungen in Salzlösungen durchgeführt, erwiesen sich diejenigen, deren [β] 〈 95 war, als heterogen und zeigten eine kleine Menge einer schneller beweglichen Komponente. Die Ergebnisse scheinen darauf hinzuweisen, daß diese Komponente die Barrierenwirkung beim β-Amylaseabbau verursacht.Bei Kartoffelamylose, die in verschiedenen Reifezuständen isoliert worden war, ist ein Anwachsen in [η] mit einer Abnahme von [β] verbunden. Die Beeinflussung der scheinbaren Molekülgröße und des [β]-Wertes durch diesen und andere Faktoren wird diskutiert. Lichtstreuungsmessungen bestätigen das Molekulargewicht und die breite Molekulargewichtsverteilung der natürlichen Amylose. Die Fraktionierung von Stärke, die mit Dimethylsulfoxyd vorbehandelt wurde, wird einer kritischen Betrachtung unterzogen.
    Notes: Samples of amyloses isolated from potato, wheat, and iris germanica starch by conventional procedures have been subfractionated by the addition of ethanol and other precipitants to a dispersion in dimethylsulphoxide. Fractions having a very wide range in limiting viscosity number [η], were obtained, but more significantly the samples differed in their β-amylolysis limits, [β]. On ultracentrifugation all samples were apparently homogeneous in dilute alkali, but most of them with [β] 〈 95 were heterogeneous in saline, and showed a minor, faster-moving component. Evidence is presented that this component may contain the barrier to β-amylolysis. For amyloses isolated from potatoes at varying stages of maturity, an increase in [η] is associated with a decrease in [β]. The significance of this and other factors controlling the apparent molecular size and the [β]-value are discussed. Lightscattering measurements confirm the molecular weight and wide molecular weight distribution of natural amylose. Fractionation of starch pretreated with dimethylsulphoxide has been critically examined.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1964.020790118
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