Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Analytical Chemistry and Spectroscopy  (3)
  • Glutamine synthetase  (3)
Collection
Keywords
Publisher
Years
  • 1
    ISSN: 0935-6304
    Keywords: Open tubular gas chromatography ; Dynamic headspace analysis ; Purge and trap ; Thermal desorption ; Reinjection ; Fourier transform infrared spectroscopy ; Volatile constituents in polymers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analytical system for the analysis of volatiles entrained in polymers is described. This system is based on a thermal desorption oven connected to a cold trap. After enrichment of headspace vapor, trapped material is reinjected and analyzed by open tubular gas chromatography/Fourier transform infrared spectroscopy, OTGC/FTIR. The thermal desorption oven is designed to provide different modes of sample introduction: use of a pyroprobe; insertion of a piece of quartz tubing with applied sample; or syringe injection. Headspace enrichment is carried out in a piece of fused silica capillary tubing filled with glass beads. The trap may be cooled either electrically using Peltier elements or with liquid nitrogen. A six-port rotary valve is used for flow switching between enrichment and reinjection modes. All system parameters, temperatures, and timed events, are controlled from the gas chromatograph. Dynamic headspace analysis is demonstrated as a method for polymer characterization.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1432-2048
    Keywords: Ammonium assimilation ; Glutamine synthetase ; Nitrate ; Phytochrome ; Sinapis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During transformation of mustard seedlings cotyledons from storage organs to photosynthetically competent leaves, a process which occurs during the first 4 d after sowing, total glutamine-synthetase (GS, EC 6.3.1.2) activity increases from zero to the high level usually observed in green leaves. In the present study we have used ion-exchange chromatography to separate possible isoforms of GS during the development of the cotyledons. The approach failed since we could only detect a single form of GS, presumably plastidic GS, under all circumstances tested. The technique of selective photooxidative destruction of plastids in situ was applied to solve the problem of GS localization. It was inferred from the data that the GS as detected by ion-exchange chromatography is plastidic GS. The regulatory role, if any, of light, nitrate and ammonium in the process of the appearance of GS in the developing cotyledons was investigated. The results show that nitrate and ammonium play only minor roles. Light, operating via phytochrome, is the major regulatory factor.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1432-2048
    Keywords: Glutamine synthetase ; Nitrate (as inductor) ; Nitrite reductase ; Phytochrome (as inductor) ; Sinapis (nitrate assimilation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The extent to which the appearances of nitrite reductase (NIR; EC 1.7.7.1) and glutamine synthetase (GS; EC 6.3.1.2) are coordinated was studied in mustard (Sinapis alba L.) seedlings. It was established by immunotitration that the increased activities of NIR and GS in the presence of light and nitrate can be attributed to the de-novo synthesis of enzyme protein. The bulk of the NIR and GS was found in the developing cotyledons. In the absence of nitrate in the growth medium there was no coordinate appearance of NIR and GS. While light strongly stimulated the appearance of GS, the level of NIR was hardly affected and remained low. On the other hand, in the presence of nitrate in the medium the appearances of NIR and GS were strictly coordinated, the GS level being considerably above that of NIR. It is argued that phytochrome-controlled synthesis of GS in the absence of nitrate is part of the mechanism to reassimilate ammonium liberated during proteolysis of storage protein and metabolism of the resulting amino acids, whereas the strictly coordinated synthesis in the presence of light and nitrate indicates the dominance of nitrate assimilation under these circumstances. The fact that the level of GS was always considerably above that of NIR appears to be a safety measure to prevent ammonium accumulation.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1432-2048
    Keywords: Glutamine synthetase ; Nitrate (as inductor) ; Nitrite reductase ; Phytochrome (as inductor) ; Sinapis (nitrate assimilation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The extent to which the appearances of nitrite reductase (NIR; EC 1.7.7.1) and glutamine synthetase (GS; EC 6.3.1.2) are coordinated was studied in mustard (Sinapis alba L.) seedlings. It was established by immunotitration that the increased activities of NIR and GS in the presence of light and nitrate can be attributed to the de-novo synthesis of enzyme protein. The bulk of the NIR and GS was found in the developing cotyledons. In the absence of nitrate in the growth medium there was no coordinate appearance of NIR and GS. While light strongly stimulated the appearance of GS, the level of NIR was hardly affected and remained low. On the other hand, in the presence of nitrate in the medium the appearances of NIR and GS were strictly coordinated, the GS level being considerably above that of NIR. It is argued that phytochrome-controlled synthesis of GS in the absence of nitrate is part of the mechanism to reassimilate ammonium liberated during proteolysis of storage protein and metabolism of the resulting amino acids, whereas the strictly coordinated synthesis in the presence of light and nitrate indicates the dominance of nitrate assimilation under these circumstances. The fact that the level of GS was always considerably above that of NIR appears to be a safety measure to prevent ammonium accumulation.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Glass and fused silica capillary columns ; Coating time and efficiency ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 0935-6304
    Keywords: Gas chromatography-mass spectrometry ; Capillary columns ; Stationary phases ; Silicones ; Thermal degradation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The applicability of capillary columns for gas chromatography is often limited by stationary phase degradation at elevated temperatures. In order to achieve a better understanding of column thermostability, column bleed products have been analyzed qualitatively by gas chromatography-mass spectrometry (GC-MS). Three silicone stationary phases were studied: SE-52, SE-54, and OV-1701. Each of these was immobilized in the columns. The proportion of cyclics containing diphenyl in column bleed from SE-52 reflected to a large extent the composition of the polymer, while for SE-54 the proportion of such cyclics was unexpectedly high. The polar moiety of OV-1701, the cyanopropyl(phenyl)siloxy unit, was found to exert a highly destabilizing effect on the polymer, and the thermal degradation products consisted mainly of cyclosiloxanes containing this unit.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...