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  • Articles  (3)
  • Populus  (2)
  • Calorimetry  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Thermodynamics of the conversion of aqueous glucose to fructose (1984)
    Springer
    Journal of solution chemistry 13 (1984), S. 523-547 
    Details
    ISSN: 1572-8927
    Keywords: Calorimetry ; enthalpy ; enzyme catalyzed reactions ; equilibrium constants ; fructose ; Gibbs energy ; glucose isomerase ; heat capacity ; high pressure liquid chromatography ; thermodynamics ; xylose isomerase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermodynamics of the conversion of aqueous glucose to fructose has been investigated using both heat conduction microcalorimetry and high pressure liquid chromatography (HPLC). The reaction was carried out in both aqueous TRIS/HCl buffer and in aqueous phosphate buffer in the pH range 7 to 8 using the enzyme glucose isomerase and the cofactors CoCl2 and MgSO4. The temperature range over which this reaction was investigated was 298.15 to 358.15 K (25–85°C). We have found that the enthalpy of reaction is independent of pH over the range 7 to 8. A combined analysis of both the HPLC and microcalorimetric data leads to the following results at 25°C: ΔGo=349±53 J-mol−1, ΔHo=2780±200 J-mol−1, and ΔC p o =76±30 J-mol−1-K−1. The stated uncertainties are based upon an analysis of both the random and systematic errors inherent in the measurements. The temperature dependence of the equilibrium constant K for the process is expressed as $$RinK = - \frac{{349}}{{298.15}} + 2780(\frac{1}{{298.15}} - \frac{1}{T}) + 76(\frac{{298.15}}{T} - 1 + \ln \frac{T}{{298.15}})$$ Comparisons are made with literature data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647222
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  • 2
    Electronic Resource
    Electronic Resource
    Pectin methylesterases from poplar cambium and inner bark: localization, properties and seasonal changes (1997)
    Springer
    Planta 202 (1997), S. 70-75 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Cambium ; Cell wall ; Pectin methylesterase ; Populus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. In the course of a study on the early events of cambial derivative differentiation in Populus × euramericana, seasonal changes in the pattern of pectin methylesterase (PME, EC 3.1.1.11) isoforms were followed. During the resting season, cell wall extracts contained mainly alkaline isoforms with an Mr around 55 kDa and optimal pH between 5.6 and 6.0. Neutral isoforms with an Mr around 35 kDa and optimal pH between 6.0 and 6.6 predominated in the extracts during the period of high meristematic activity. In the active cambial initials and in their immediate derivatives, the enzymes were immunolocalized exclusively in the dictyosomes. In older cells, they were present both in dictyosomes and in wall junctions. These results indicate that exportation of neutral PMEs towards the walls might be considered as an early marker of differentiation in cambial derivatives.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050104
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  • 3
    Electronic Resource
    Electronic Resource
    Pectin immunolocalization and calcium visualization in differentiating derivatives from poplar cambium (1997)
    Springer
    Protoplasma 199 (1997), S. 151-160 
    Details
    ISSN: 1615-6102
    Keywords: Calcium ; Cambium ; Ionic microscopy ; Immunolocalization ; Pectins ; Populus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Calcium distribution and pectin esterification patterns in the cambial zone of poplar branches were studied with ionic microscopy and immunological tools respectively. Dynamic changes correlating with cell growth and cell differentiation were observed both on the xylem and on the phloem sides. In expanding cell walls of xylem derivatives, unesterified pectins were restricted to cell junctions and middle lamellae, occasionally accompanied by calcium ions. In contrast, in differentiating and mature phloem cells, acidic pectins and Ca2+ were present all over the walls leading to early stiffening of the polysaccharide network. Significant labelling was detected with JIM5 antibodies in some dictyosomes suggesting exocytosis of low methylated polymers towards the cell walls. At cell junctions, unesterified pectins might originate from the activity of pectinmethylesterases localized in these areas. Thus un- and deesterified pectins might be located in different cell wall domains whose distribution, varying with cell type, will confer specific extensibility to the wall matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294503
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