Determination of transport constants of isolated Nitella cell walls

1968 ◽  
Vol 46 (4) ◽  
pp. 317-327 ◽  
Author(s):  
M. T. Tyree
Keyword(s):  
Activation Energy ◽  
Cell Wall ◽  
Diffusion Coefficient ◽  
Cell Walls ◽  
Transport Coefficients ◽  
Irreversible Thermodynamics ◽  
Kcal Mole ◽  
Limiting Value ◽  
Nitella Flexilis

Transport coefficients LPP, LPE, LEP, and LEE for electrokinetic equations according to irreversible thermodynamics, the Onsager coefficients, were measured for isolated Nitella flexilis cell walls in KCl solutions ranging from 10−4 to 100 normal. LPP and LPE (= LEP) were found to be independent of KCl concentration and equal to 1.4 × 10−6 cm3 sec−1 cm−2 (joule cm−3)−1 cm and 6 × 10−5 cm3 sec−1 cm−2 volt−1 cm respectively. LEE was a function of the salt concentration, reaching a limiting value of about 1.2 × 10−3 mho cm−1 in 10−4 N KCl. The activation energy for movement of KCl in cell walls was found to be 4.33 Kcal mole−1; the diffusion coefficient for KCl in cell walls was calculated by two methods to be 8 × 10−6 cm2 sec−1; and the concentration of the fixed ions in Nitella cell walls from the above data was estimated at greater than 0.04 equivalent per liter of cell wall. Electroosmosis in Nitella membranes is re-examined in the light of the measured transport coefficients and it is concluded that under proper conditions the cell wall of Nitella can contribute significantly (~20% or more) to the observed electroosmosis of living Nitella cells.

Vulcanization of Elastomers. 23. The Chemical Kinetics of Vulcanization Reactions and The Physical Properties of The Vulcanizates. I

1960 ◽  
Vol 33 (2) ◽  
pp. 335-341
Author(s):  
Walter Scheele ◽  
Karl-Heinz Hillmer
Keyword(s):  
Activation Energy ◽  
Physical Properties ◽  
Chemical Kinetics ◽  
Kcal Mole ◽  
First Order ◽  
Equilibrium Swelling ◽  
Kinetics Of ◽  
Kinetics Of Vulcanization ◽  
Limiting Value ◽  
Good Agreement

Abstract As a complement to earlier investigations, and in order to examine more closely the connection between the chemical kinetics and the changes with vulcanization time of the physical properties in the case of vulcanization reactions, we used thiuram vulcanizations as an example, and concerned ourselves with the dependence of stress values (moduli) at different degrees of elongation and different vulcanization temperatures. We found: 1. Stress values attain a limiting value, dependent on the degree of elongation, but independent of the vulcanization temperature at constant elongation. 2. The rise in stress values with the vulcanization time is characterized by an initial delay, which, however, is practically nonexistent at higher temperatures. 3. The kinetics of the increase in stress values with vulcanization time are both qualitatively and quantitatively in accord with the dependence of the reciprocal equilibrium swelling on the vulcanization time; both processes, after a retardation, go according to the first order law and at the same rate. 4. From the temperature dependence of the rate constants of reciprocal equilibrium swelling, as well as of the increase in stress, an activation energy of 22 kcal/mole can be calculated, in good agreement with the activation energy of dithiocarbamate formation in thiuram vulcanizations.

Chemical analysis of isolated cell walls of Gram-positive bacteria and determination of the cell wall to cell mass ratio

1997 ◽  
Vol 28 (2) ◽  
pp. 147-157 ◽  
Author(s):  
Albert van der Wal ◽  
Willem Norde ◽  
Bernd Bendinger ◽  
Alexander J.B Zehnder ◽  
Johannes Lyklema
Keyword(s):  
Cell Wall ◽  
Chemical Analysis ◽  
Cell Walls ◽  
Cell Mass ◽  
Mass Ratio ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Isolated Cell

scholarly journals Two Novel Techniques for Determination of Polysaccharide Cross-Links Show that Crh1p and Crh2p Attach Chitin to both β(1-6)- and β(1-3)Glucan in the Saccharomyces cerevisiae Cell Wall

2009 ◽  
Vol 8 (11) ◽  
pp. 1626-1636 ◽  
Author(s):  
Enrico Cabib
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Wall ◽  
Acetic Acid ◽  
Yeast Cell ◽  
Cell Walls ◽  
Double Mutant ◽  
The Other ◽  
Cross Links

ABSTRACT Previous work, using solubilization of yeast cell walls by carboxymethylation, before or after digestion with β(1-3)- or β(1-6)glucanase, followed by size chromatography, showed that the transglycosylases Crh1p and Crh2p/Utr2p were redundantly required for the attachment of chitin to β(1-6)glucan. With this technique, crh1Δ crh2Δ mutants still appeared to contain a substantial percentage of chitin linked to β(1-3)glucan. Two novel procedures have now been developed for the analysis of polysaccharide cross-links in the cell wall. One is based on the affinity of curdlan, a β(1-3)glucan, for β(1-3)glucan chains in carboxymethylated cell walls. The other consists of in situ deacetylation of cell wall chitin, generating chitosan, which can be extracted with acetic acid, either directly (free chitosan) or after digestion with different glucanases (bound chitosan). Both methodologies indicated that all of the chitin in crh1Δ crh2Δ strains is free. Reexamination of the previously used procedure revealed that the β(1-3)glucanase preparation used (zymolyase) is contaminated with a small amount of endochitinase, which caused erroneous results with the double mutant. After removing the chitinase from the zymolyase, all three procedures gave coincident results. Therefore, Crh1p and Crh2p catalyze the transfer of chitin to both β(1-3)- and β(1-6)glucan, and the biosynthetic mechanism for all chitin cross-links in the cell wall has been established.

scholarly journals UDP-GLYCOSYLTRANSFERASE 72E3 Plays a Role in Lignification of Secondary Cell Walls in Arabidopsis

2020 ◽  
Vol 21 (17) ◽  
pp. 6094
Author(s):  
Fabien Baldacci-Cresp ◽  
Julien Le Roy ◽  
Brigitte Huss ◽  
Cédric Lion ◽  
Anne Créach ◽  
...  
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Lignin Content ◽  
Mutant Cell ◽  
Subsequent Investigation ◽  
Secondary Cell Walls ◽  
Chemical Determination ◽  
Safranin O

Lignin is present in plant secondary cell walls and is among the most abundant biological polymers on Earth. In this work we investigated the potential role of the UGT72E gene family in regulating lignification in Arabidopsis. Chemical determination of floral stem lignin contents in ugt72e1, ugt72e2, and ugt72e3 mutants revealed no significant differences compared to WT plants. In contrast, the use of a novel safranin O ratiometric imaging technique indicated a significant increase in the cell wall lignin content of both interfascicular fibers and xylem from young regions of ugt72e3 mutant floral stems. These results were globally confirmed in interfascicular fibers by Raman microspectroscopy. Subsequent investigation using a bioorthogonal triple labelling strategy suggested that the augmentation in lignification was associated with an increased capacity of mutant cell walls to incorporate H-, G-, and S-monolignol reporters. Expression analysis showed that this increase was associated with an up-regulation of LAC17 and PRX71, which play a key role in lignin polymerization. Altogether, these results suggest that UGT72E3 can influence the kinetics of lignin deposition by regulating monolignol flow to the cell wall as well as the potential of this compartment to incorporate monomers into the growing lignin polymer.

Nature des liaisons de l'ion calcium dans la paroi de Nitella flexilis

1978 ◽  
Vol 56 (12) ◽  
pp. 1439-1443 ◽  
Author(s):  
R. Wuytack ◽  
C. Gillet
Keyword(s):  
Cell Wall ◽  
Calcium Ions ◽  
Cell Walls ◽  
External Medium ◽  
Conductivity Measurements ◽  
Carboxylic Groups ◽  
Spectrophotometric Titrations ◽  
Nitella Flexilis

Spectrophotometric titrations and conductivity measurements show that Nitella cell walls contain nonexchangeable Ca2+ cations which are probably chelated by COO− anions and donor groups such as OH (from polysaccharides) or NH (from proteins).A large part of these calcium ions are removed by acidification of the external medium. Subsequent augmentation of COO− groups increases the number of exchange sites available for H+ and K+ ions. The variation of the carboxylic groups concentration (α) is thus not fully accounted for by the pK of polygalacturonic acids but is also related to changes within the constitutive calcium of the cell wall.

Le Stigmidium lecidellae sp.nov. et remarques sur le genre Stigmidium (champignons lichénicoles non lichénisés, Ascomycètes)

1995 ◽  
Vol 73 (4) ◽  
pp. 662-672 ◽  
Author(s):  
Claude Roux ◽  
Olivier Bricaud ◽  
Didier Le Coeur ◽  
Dagmar Triebel
Keyword(s):  
Cell Wall ◽  
Key Words ◽  
Cell Walls ◽  
Species Level ◽  
Lichenicolous Fungi ◽  
Cresyl Blue ◽  
Taxonomic Key

Stigmidium lecidellae Triebel, Roux et Le Coeur sp.nov., a mild pathogenic lichenicolous fungus growing on the apothecia of Lecidella elaeochroma (Ach.) M. Choisy is described in detail and compared with other species of Stigmidium that grow on the apothecia of the host. The staining of parts of cell walls with cresyl blue is constant at species level and, therefore, is taxonomically relevant in the genus Stigmidium. The dye also allows to distinguish some ultrastructural details of the vegetative hyphal cells, asci, and ascospores. Among the fungi species growing on the apothecia of lichens, three groups are distinguished on the basis of their hamathecial structure, one of which should be excluded from the genus Stigmidium and included in the genus Sphaerellothecium. A key to the determination of the species is presented. Key words: lichenicolous fungi, Stigmidium, Sphaerellothecium, taxonomy, taxonomic key, cell wall, staining reactions, hamathecium.

scholarly journals Determination of Subunit Composition of Clostridium cellulovorans Cellulosomes That Degrade Plant Cell Walls

2002 ◽  
Vol 68 (4) ◽  
pp. 1610-1615 ◽  
Author(s):  
Koichiro Murashima ◽  
Akihiko Kosugi ◽  
Roy H. Doi
Keyword(s):  
Cell Wall ◽  
Plant Cell ◽  
Cell Walls ◽  
Plant Cell Wall ◽  
Scaffolding Protein ◽  
Plant Cell Walls ◽  
Higher Plant ◽  
Clostridium Cellulovorans ◽  
Plant Cell Wall Degradation

ABSTRACT Clostridium cellulovorans produces a cellulase enzyme complex (cellulosome). In this study, we isolated two plant cell wall-degrading cellulosomal fractions from culture supernatant of C. cellulovorans and determined their subunit compositions and enzymatic activities. One of the cellulosomal fractions showed fourfold-higher plant cell wall-degrading activity than the other. Both cellulosomal fractions contained the same nine subunits (the scaffolding protein CbpA, endoglucanases EngE and EngK, cellobiohydrolase ExgS, xylanase XynA, mannanase ManA, and three unknown proteins), although the relative amounts of the subunits differed. Since only cellobiose was released from plant cell walls by the cellulosomal fractions, cellobiohydrolases were considered to be key enzymes for plant cell wall degradation.

Vulcanization of Elastomers. 21. Vulcanization of Natural Rubber with Thiuram Disulfides. VI

1959 ◽  
Vol 32 (2) ◽  
pp. 566-576
Author(s):  
Walter Scheele ◽  
Klaus Hummel
Keyword(s):  
Activation Energy ◽  
Natural Rubber ◽  
Temperature Dependence ◽  
Sulfur Content ◽  
Rate Constants ◽  
Order Reaction ◽  
First Order Reaction ◽  
Kcal Mole ◽  
First Order ◽  
Limiting Value

Abstract Bound sulfur in a pure thiuram vulcanizate increases relatively rapidly at first at all temperatures, reaches a poorly defined maximum at about 27 to 30%, independent of temperature, and then recedes slightly to reach a limiting value of 25% also independent of temperature, based on the original thiuram disulfide. The rise in sulfur content at the start points to a temperature-independent limiting value of 33%. It is shown that the combination of sulfur in this region initially follows a first order reaction, and goes at the same rate as the reduction in concentration of thiuram disulfide. It can be seen from the above that sulfur may be combined in thiuram vulcanization without simultaneous crosslinking. The dithiocarbamate formation increases rapidly in the region of longer vulcanization times, after the maximum in bound sulfur has been reached, without further combination of sulfur with the vulcanizate. The rate constants for thiuram decrease, for dithiocarbamate increase and for sulfur combination were calculated. The temperature dependence of each of these reactions has practically the same activation energy, 23 kcal/mole. The bound sulfur content of the vulcanizates in pure thiuram vulcanizations is no criterion of the state of vulcanization.

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