Comparison between specific surface complexation and Donnan ion-exchange models for describing the adsorption of cations on kraft fibres – literature evidence and EXAFS study of Cu(II) binding

2010 ◽  
Vol 25 (2) ◽  
pp. 178-184 ◽  
Author(s):  
Ola Sundman ◽  
Per Persson ◽  
Lars-Olof Öhman
Keyword(s):  
Ionic Strength ◽  
Ion Exchange ◽  
Metal Ion ◽  
Experimental Conditions ◽  
Cellulose Fibres ◽  
Metal Ion Adsorption ◽  
Literature Evidence ◽  
Trivalent Cations ◽  
Exafs Study ◽  
Low Ionic Strength

Abstract A compilation of the applied experimental conditions when studying metal ion adsorption onto kraft fibres, and the resulting conclusion, revealed that the ionic strength conditions used during the experiments were an important dividing factor. At low ionic strengths, the conclusion has regularly been that the Donnan ion-exchange model could correctly predict the adsorption while, at higher ionic strengths, it has often been concluded that the formation of specific metal-ion fibre complexes must be assumed. To study this apparent influence from the presence of monovalent sodium ions, Cu K-edge EXAFS spectra of Cu2+ ions adsorbed to kraft fibres were collected in media of “0” to 100 mM NaCl. Combined with previous data, these measurements confirmed that at very low ionic strength, the importance of specific interactions between the chemically modified cellulose fibres and the Cu(II) ions significantly decreased. For a detailed description of the adsorption phenomenon, both types of interactions must be considered simultaneously. For most technical and engineering applications, however, the Donnan model can be used at low ionic strength conditions, i.e. I ≲ 10 mM. At higher ionic strengths, though, the inclusion of specific complexes in the model is necessary for correctly describing the adsorption of di- and trivalent cations with strong complex forming properties.

scholarly journals Selective factor VIII and V inactivation by iminodiacetate ion exchange resin through metal ion adsorption*

2008 ◽  
Vol 142 (6) ◽  
pp. 962-970 ◽  
Author(s):  
Masahiro Takeyama ◽  
Keiji Nogami ◽  
Masahiro Okuda ◽  
Yoshihiko Sakurai ◽  
Tomoko Matsumoto ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Factor Viii ◽  
Metal Ion ◽  
Exchange Resin ◽  
Ion Exchange Resin ◽  
Ion Adsorption ◽  
Metal Ion Adsorption

Correlation between Ca2+-ATPase activity of rat islet cells and insulin secretion

1992 ◽  
Vol 134 (2) ◽  
pp. 221-225 ◽  
Author(s):  
C. M. Gronda ◽  
G. B. Diaz ◽  
J. P. F. C. Rossi ◽  
J. J. Gagliardino
Keyword(s):  
Enzyme Activity ◽  
Insulin Secretion ◽  
Ionic Strength ◽  
Atpase Activity ◽  
Islet Cells ◽  
Experimental Conditions ◽  
Physiological Regulation ◽  
Enhancing Effect ◽  
Cellular Targets ◽  
Low Ionic Strength

ABSTRACT Using medium with a low ionic strength, a low concentration of Ca2+ and Mg2+ and devoid of K+, we have measured Ca2+-ATPase activity in the homogenates of rat islets preincubated for 3 min with several hormones in the presence of 3·3 mmol glucose/l. Insulin secretion was also measured in islets incubated for 5 min under identical experimental conditions. Islets preincubated with glucose (3·3 mmol/l) and glucagon (1·4 μmol/l) plus theophylline (10 mmol/l), ACTH (0·11 nmol/l), bovine GH (0·46 μmol/l), prolactin (0·2 μmol/l) or tri-iodothyronine (1·0 nmol/l) have significantly lower Ca2+-ATPase activity than those preincubated with only 3·3 mmol glucose/l. All these hormones increased the release of insulin significantly. Dexamethasone (0·1 μmol/l) and somatostatin (1·2 μmol/l) enhanced the Ca2+-ATPase activity while adrenaline (10 μmol/l) did not produce any significant effect on the activity of the enzyme. These hormones decreased the release of insulin significantly. These results demonstrated that islet Ca2+-ATPase activity was modulated by the hormones tested. Their inhibitory or enhancing effect seemed to be related to their effect on insulin secretion; i.e. those which stimulated the secretion of insulin inhibited the activity of the enzyme and vice versa. Hence, their effect on insulin secretion may be due, in part, to their effect on enzyme activity and consequently on the concentration of cytosolic Ca2+. These results reinforce the assumption that Ca2+-ATPase activity participates in the physiological regulation of insulin secretion, being one of the cellular targets for several agents which affect this process. Journal of Endocrinology (1992) 134, 221–225

Activation and inactivation of acetylcholinesterase by metal ions

1981 ◽  
Vol 59 (9) ◽  
pp. 728-735 ◽  
Author(s):  
George Tomlinson ◽  
Bulent Mutus ◽  
Ian McLennan
Keyword(s):  
Ionic Strength ◽  
Metal Ions ◽  
Metal Ion ◽  
Prolonged Exposure ◽  
Chelating Agent ◽  
High Ionic Strength ◽  
Metal Ion Binding ◽  
Peripheral Site ◽  
Metal Ion Effects ◽  
Low Ionic Strength

The kinetic consequences of acetylcholinesterase peripheral site occupation by metal ions were examined using three substrates; acetylthiocholine, p-nitrophenylacetate, and 7-(dimethylcarbamoyloxy)-N-methylquinolinium iodide. Two classes of metal ion effects were noted: activation by a group including Mg2+, Ca2+, Mn2+, and Na+, and inactivation by a second group which to date includes Zn2+, Cd2+, Hg2+, Ni2+, Cu2+, and Pb2+. Activation is demonstrable only in solutions of low ionic strength whereas inactivation can be readily observed in solutions of both low and high ionic strength. Activation appears to be due to a combination of metal ion binding and ionic strength effects and involves binding to peripheral sites which are distinct from those which bind organic cationic activators such as gallamine, propidium, and 7-(dimethylcarbamoyloxy)-N-methylquinolinium. The principal activating effect is on the deacylation phase of the enzyme–substrate reaction. Inactivators effect a slow conversion of the enzyme to an unreactive form. The kinetics of inactivation are biphasic at low ionic strength but become essentially monophasic at high ionic strength. More than 80% of the enzyme activity can be recovered upon addition of EDTA provided the chelating agent is added immediately following completion of the inactivation process. Prolonged exposure to inactivators results in a progressive decrease in the amount of recoverable activity. Although peripheral ligand interactions may result in a variety of catalytic site conformations, the macroscopic properties can be accounted for in terms of three ligand-dependent states of the enzyme in which catalytic ability (actual or potential) is retained, and a fourth denatured state.

scholarly journals Conformational variation in superhelical deoxyribonucleic acid

1978 ◽  
Vol 171 (1) ◽  
pp. 281-283 ◽  
Author(s):  
A M Campbell
Keyword(s):  
Light Scattering ◽  
Ionic Strength ◽  
Structural Transition ◽  
Deoxyribonucleic Acid ◽  
Dna Molecules ◽  
Experimental Conditions ◽  
Low Ionic Strength

Sedimentation experiments have shown that superhelical DNA undergoes a sharp structural transition at low ionic strength. Light-scattering experiments show that this is due to a change in conformation of the DNA rather than to a change in interactions among DNA molecules. The results show that two possible conformations can occur for superhelical DNA under routine experimental conditions and may explain the discrepancies in the number of early unwinding sites exposed by different techniques.

scholarly journals The Effect of Low Ionic Strength Extracellular Solutions on the Resting Potential in Skeletal Muscle Fibers

1967 ◽  
Vol 50 (6) ◽  
pp. 1485-1497
Author(s):  
David Holtzman
Keyword(s):  
Ionic Strength ◽  
Resting Potential ◽  
Sartorius Muscle ◽  
Extracellular Solution ◽  
Experimental Conditions ◽  
Nacl Concentration ◽  
Tip Potential ◽  
Low Ionic Strength ◽  
Relationship Of ◽  
The Relationship

Intracellular measurements of the resting potential were made in fibers of the frog sartorius muscle in solutions of varying salt composition and concentration to determine the effects of low ionic strength extracellular solutions on the resting potential. Changes in the glass microelectrode tip potential in low ionic strength solutions were minimized by adding ThCl4 to the extracellular solution. These experimental conditions allowed measurement of the relationship of the resting potential to the concentration of the salt in the extracellular solution by replacing it with the nonionic substance, sucrose. Substitution of sucrose for the extracellular NaCl produced a stable depolarization which was logarithmically related to the NaCl concentration. Substitution of sucrose for choline Cl, instead of NaCl, produced the same degree of depolarization. When Na salts of anions less permeable than chloride (Br, I, NO3) were used, the resting potentials in 116 mM solutions were close to those with chloride (±3mv). The depolarizations produced in low ionic strength solutions of these salts were significantly less than those with chloride.

scholarly journals Determination of free metal ion concentrations with AGNES in low ionic strength media

2013 ◽  
Vol 689 ◽  
pp. 276-283 ◽  
Author(s):  
D. Aguilar ◽  
C. Parat ◽  
J. Galceran ◽  
E. Companys ◽  
J. Puy ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Metal Ion ◽  
Ion Concentrations ◽  
Low Ionic Strength ◽  
Free Metal ◽  
Free Metal Ion
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