scholarly journals A theory relating the action of salts on bacterial respiration to their influence on the solubility of proteins

1947 ◽  
Vol 134 (875) ◽  
pp. 181-201 ◽  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Dehydrogenase Activity ◽  
Halophilic Bacteria ◽  
Convincing Evidence ◽  
Effect Of Temperature ◽  
Bacterial Respiration ◽  
Concentrated Solutions ◽  
Salting Out ◽  
Intact Cells

Evidence has been presented indicating that the action of concentrated solutions of salts on bacterial respiration may be partly explained in terms of salting-out. It has been suggested that the material upon which this action is exerted is probably one of the proteins concerned in respiration, perhaps a dehydrogenating enzyme. This theory provides satisfactory explanations for: ( a ) the relation between salt con­centration and rate of respiration or dehydrogenase activity; ( b ) the effect of temperature on this relation; and ( c ) the effect of pH on this relation, if it is further supposed that only the zwitterionic fraction of the protein is involved. The relative actions of various salts are in fair agreement with this suggestion, but provide no very convincing evidence either for or against it. The chief point of difficulty lies in the range of concentration over which the action is manifest. With halophilic bacteria, the evidence is consonant with the above view if the protein involved is one of high molecular weight. With normal organisms the salt concentra­tions are much lower than those causing salting-out. There is a little evidence that in normal organisms the dehydrogenating enzymes are less sensitive to salts than the intact cells, which may be the source of the discrepancy. No reason for this can yet be suggested, but the property must be absent from the enzymes of halophilic organisms, and whatever it is, its absence must be the foundation of the halophilic character.

scholarly journals Isolation and characterization of a large, neurite-associated glycoconjugate from neuroblastoma cells

1983 ◽  
Vol 96 (3) ◽  
pp. 661-668 ◽  
Author(s):  
EAG Chernoff ◽  
GA Maresh ◽  
LA Culp
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Neuroblastoma Cell ◽  
Neuroblastoma Cells ◽  
Cell Fraction ◽  
Serum Starvation ◽  
Affinity Column ◽  
Human Neuroblastoma ◽  
Intact Cells ◽  
Isolation And Characterization

A high molecular weight glycoconjugate has been isolated from neurite-producing neuronal tumor cells in culture and has been designated as I(0) based on its elution characteristics in gel filtration chromatography. This molecule cannot be found in a variety of nonneuronal cells. I(0) is found in the substratum-attached material or cell fraction of neurite-producing neuroblastoma cells, depending upon culture conditions. It is found in the substratum-bound fraction of B104 rat neuroblastoma cells during serum starvation and in the EGTA-detached cell fraction of B104 cells grown in chemically defined N2 medium. It occurs only in the cell fraction of the human neuroblastoma line Platt. Examination of behavioral variants of the B104 rat line further strengthens the association of I(0) with neurite production; the constitutive neurite-producing E(R)B9 variant contains I(0) while the non-neurite-producing E(R)A11 variant does not. I(0) is large, eluting in the void volume of sepharose-CL2B columns. Radioiodination of intact cells with lactoperoxidase shows I(0) to be a cell surface component. Metabolic radiolabeling studies show that it contains a high proportion of polysaccharide to protein, does not contain mannose, and is unsulfated. Alkaline borohydride reduction release two size classes of large polysaccharide chain. The alkaline reduction results, along with the mannose incorporation studies, show the presence of O-glycosidic linkages and few, if any, N-linkages. Resistance to nitrous acid deamination, insensitivity to glycosaminoglycan lyases, and the absence of sulfation, indicate that I(0) does not contain the glycosaminoglycans hyaluronic acid, chondroitin-, dermatan-, or heparin- sulfates. Affinity column chromatography reveals high binding affinity of I(0) to polyornithine and no binding to gelatin (collagen) or the glycosaminoglycans hyaluronate and heparin. These studies describe a unique high molecular weight glycoconjugate on the surface of neurite-producing neuroblastoma cell lines from two species.

scholarly journals ISOLATION AND PARTIAL CHARACTERIZATION OF MACRO- AND MICRONUCLEI FROM PARAMECIUM AURELIA

1972 ◽  
Vol 53 (1) ◽  
pp. 105-115 ◽  
Author(s):  
Donald J. Cummings
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Calcium Ions ◽  
Gel Electrophoresis ◽  
Partial Characterization ◽  
Intact Cells ◽  
Molecular Weights ◽  
High Molecular Weight Species ◽  
Nonionic Detergents

A method was developed for the isolation of macro- and micronuclei from Paramecium aurelia. This method utilized ionic and nonionic detergents to rupture the intact cells, calcium ions and spermidine were employed to protect the nuclei, and the nuclei were purified by centrifugation. Macronuclei consisted of 22% DNA, 10% RNA, and 68% protein. Micronuclei were composed of 9% DNA, 11% RNA, and 80% protein. DNA from both macro- and micronuclei had a density of 1.687 g/cc in CsCl and 1.417 g/cc in Cs2SO4. These values corresponded to G + C content of about 23%. The RNA of macronuclei was examined by gel electrophoresis, and two high molecular weight species were identified having molecular Weights of 1.3 x 106 and 2.8 x 106 daltons. Three syngens were studied, and in each case the conditions for isolation of the nuclei were the same and no differences were observed in the properties of the nuclei.

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