scholarly journals THE SIZE OF THE CELLULOSE MICROFIBRIL

1963 ◽  
Vol 17 (1) ◽  
pp. 105-109 ◽  
Author(s):  
J. Ross Colvin
Keyword(s):  
Experimental Evidence ◽  
Cellulose Microfibril ◽  
Phosphotungstic Acid ◽  
Negative Staining ◽  
Cellulose Microfibrils ◽  
Direct Experimental Evidence ◽  
Native Cellulose ◽  
Lateral Width ◽  
The Difference

Recently the lateral width of the cellulose microfibril has been estimated as 30 A rather than about 150 to 200 A, by extrapolation of data from model shadowing experiments. The difference was attributed to a layer of metal deposited during shadowing. However, direct photographs of the same microfibrils parallel and perpendicular to the direction of shadowing, of unshadowed portions of microfibrils compared with shadowed portions of the same microfibrils, of silver-stained unshadowed microfibrils, and of unshadowed, unstained segments of microfibrils give no evidence of a layer of metal of this thickness in material shadowed under normal conditions. Furthermore, the evidence for microfibril strands of about 35 A in width from negative-staining experiments is subject to a bias from the form of the filaments and from variable positive adsorption of phosphotungstic acid by cellulose. Consequently, the conclusion that the true lateral width of native cellulose microfibrils is about one-fifth of the presently accepted value is not yet justified by unequivocal direct experimental evidence.

Overexpression of cysteine dioxygenase reduces intracellular cysteine and glutathione pools in HepG2/C3A cells

2007 ◽  
Vol 293 (1) ◽  
pp. E62-E69 ◽  
Author(s):  
John E. Dominy ◽  
Jesse Hwang ◽  
Martha H. Stipanuk
Keyword(s):  
Steady State ◽  
Experimental Evidence ◽  
Cysteine Dioxygenase ◽  
Wild Type ◽  
Hepatic Expression ◽  
Direct Experimental Evidence ◽  
Homeostatic Response ◽  
Catabolic Enzyme ◽  
In Cells

Cysteine levels are carefully regulated in mammals to balance metabolic needs against the potential for cytotoxicity. It has been postulated that one of the major regulators of intracellular cysteine levels in mammals is cysteine dioxygenase (CDO). Hepatic expression of this catabolic enzyme increases dramatically in response to increased cysteine availability and may therefore be part of a homeostatic response to shunt excess toxic cysteine to more benign metabolites such as sulfate or taurine. Direct experimental evidence, however, is lacking to support the hypothesis that CDO is capable of altering steady-state intracellular cysteine levels. In this study, we expressed either the wild-type (WT) or a catalytically inactivated mutant (H86A) isoform of CDO in HepG2/C3A cells (which do not express endogenous CDO protein) and cultured them in different concentrations of extracellular cysteine. WT CDO, but not H86A CDO, was capable of reducing intracellular cysteine levels in cells incubated in physiologically relevant concentrations of cysteine. WT CDO also decreased the glutathione pool and potentiated the toxicity of CdCl2. These results demonstrate that CDO is capable of altering intracellular cysteine levels as well as glutathione levels.

A TEMPO-catalyzed oxidation-reduction method to probe surface and anhydrous crystalline-core domains of cellulose microfibril bundles

2021 ◽  
Author(s):  
Tanîa M. Shiga ◽  
Haibing Yang ◽  
Bryan W. Penning ◽  
Anna T. Olek ◽  
Maureen C. McCann ◽  
...  
Keyword(s):  
Secondary Wall ◽  
Cellulose Microfibril ◽  
Reduction Method ◽  
Cellulose Microfibrils ◽  
Cotton Fibers ◽  
Uronic Acids ◽  
Oxidation Reduction ◽  
Crystalline Core ◽  
Secondary Wall Formation ◽  
Catalyzed Oxidation

Abstract A modified TEMPO-catalyzed oxidation of the solvent-exposed glucosyl units of cellulose to uronic acids, followed by carboxyl reduction with NaBD 4 to 6-deutero- and 6,6-dideuteroglucosyl units, provided a robust method for determining relative proportions of disordered amorphous, ordered surface chains, and anhydrous core-crystalline residues of cellulose microfibrils inaccessible to TEMPO. Both glucosyl residues of cellobiose units, digested from amorphous chains of cellulose with a combination of cellulase and cellobiohydrolase, were deuterated, whereas those from anhydrous chains were undeuterated. By contrast, solvent-exposed and anhydrous residues alternate in surface chains, so only one of the two residues of cellobiosyl units was labeled. Although current estimates indicate that each cellulose microfibril comprises only 18 to 24 (1 , 4)- b eta-D-glucan chains, we show here that microfibrils of walls of Arabidopsis leaves and maize coleoptiles, and those of secondary wall cellulose of cotton fibers and poplar wood, bundle into much larger macrofibrils, with 67 to 86% of the glucan chains in the anhydrous domain. These results indicate extensive bundling of microfibrils into macrofibrils occurs during both primary and secondary wall formation. We discuss how, beyond lignin, the degree of bundling into macrofibrils contributes an additional recalcitrance factor to lignocellulosic biomass for enzymatic or chemical catalytic conversion to biofuel substrates.

Fine Structure of Native Cellulose Microfibrils

Nature ◽  
1964 ◽  
Vol 204 (4964) ◽  
pp. 1155-1157 ◽  
Author(s):  
R. ST. JOHN MANLEY
Keyword(s):  
Fine Structure ◽  
Cellulose Microfibrils ◽  
Native Cellulose

Large magnetostriction and direct experimental evidence for anisotropy compensation in Tb0.4−xNdxDy0.6(Fe0.8Co0.2)1.93 Laves compounds

2014 ◽  
Vol 137 ◽  
pp. 274-276 ◽  
Author(s):  
J.J. Liu ◽  
Z.B. Pan ◽  
X.Y. Liu ◽  
Z.R. Zhang ◽  
X.H. Song ◽  
...  
Keyword(s):  
Experimental Evidence ◽  
Direct Experimental Evidence

scholarly journals THE COEXISTENCE OF PROTOZOAN-LIKE PARASITES AND MENINGOENCEPHALITIS IN MICE

1924 ◽  
Vol 40 (1) ◽  
pp. 51-62 ◽  
Author(s):  
E. V. Cowdry ◽  
F. M. Nicholson
Keyword(s):  
Experimental Evidence ◽  
Small Proportion ◽  
Clinical Symptoms ◽  
The Other ◽  
Laboratory Mice ◽  
Direct Experimental Evidence

A small proportion of laboratory mice, which appear to be normal, are in reality suffering from an obscure disease characterized by the presence of marked meningoencephalitic lesions which are often accompanied by protozoan-like parasites. Both the lesions and the parasites closely resemble others previously reported in rabbits, which likewise fail to reveal themselves by pronounced clinical symptoms. In the absence of direct experimental evidence it is suggested either that one species of parasite is capable of producing the lesions in both animals, or else that we have to do with two kinds of parasites which are closely related and, in the stages thus far observed, are indistinguishable one from the other.

scholarly journals Polymorphism in a Flagellar-shape Mutant of Salmonella typhimurium

Microbiology ◽  
2000 ◽  
Vol 81 (1) ◽  
pp. 37-45 ◽  
Author(s):  
T. Iino ◽  
Tomoko Oguchi ◽  
T. Kuroiwa
Keyword(s):  
Salmonella Typhimurium ◽  
Phosphotungstic Acid ◽  
Phase 1 ◽  
Marked Change ◽  
Uranyl Acetate ◽  
Negative Staining ◽  
Wave Form ◽  
Specimen Preparation ◽  
Physico Chemical ◽  
Wave Forms

A flagellar-shape mutant, designated ‘polymorphous’, was isolated from a normal flagella strain of Salmonella typhimurium. The mutant produces normal flagella in phase 1 and polymorphous flagella in phase 2. The polymorphous flagella are either straight or possess one of the four distinct wave-forms, namely M, S, N or C, when observed with an electron microscope after negative staining with phosphotungstic acid or uranyl acetate. Conversions between the four wave-forms were found to be brought about mainly by a change in the degree of twisting of longitudinal strands around the axis of a flagella filament, without marked change in the relative lengths of the outermost and innermost strands. The major fraction of the polymorphous mutant flagella showed the N-form under any conditions of specimen preparation. The remaining four forms appeared as minor fractions in various proportions. Specimens fixed with formalin showed less pronounced polymorphism than unfixed ones. Negative staining with uranyl acetate was more effective than with phosphotungstic acid for observing polymorphism. Even though more than one form appeared among the polymorphous flagella, each individual flagellum comprised a single form except for a rare coexistence of S and N. The same form of flagella tended to coexist in a bacterium in a heteromorphously flagellated cell population. It was concluded that the conformation and arrangement of the flagellin molecules responsible for wave-form result from strong mutual interactions between the neighbouring molecules along the flagellar filaments and also, to a lesser extent, between the neighbouring filaments in a flagellar bundle, as well as being influenced by the physico-chemical environment.

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