scholarly journals Dominating Role of Ionic Strength in the Sedimentation of Nano-TiO2in Aquatic Environments

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Guang’an He ◽  
Rui Chen ◽  
Shushen Lu ◽  
Chengchun Jiang ◽  
Hong Liu ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Natural Organic Matter ◽  
Divalent Cations ◽  
Environmental Water ◽  
Orthogonal Experimental Design ◽  
Aquatic Environments ◽  
Monovalent Cations ◽  
Sedimentation Behavior ◽  
Low Levels

Various factors affect the sedimentation behavior of nanotitanium dioxide (n-TiO2) in water. Accordingly, this study aimed to select the dominating factor. An index of sedimentation efficiency related to n-TiO2concentration was applied to precisely describe the n-TiO2sedimentation behavior. Ionic strength (IS), natural organic matter (NOM) content, and pH were evaluated in sedimentation experiments. An orthogonal experimental design was used to sequence the affecting ability of these factors. Furthermore, simulative sedimentation experiments were performed. The n-TiO2sedimentation behavior was only affected by pH and NOM content at low levels of IS. Moreover, divalent cations can efficiently influence the n-TiO2sedimentation behavior compared with monovalent cations at fixed IS. Seven different environmental water samples were also used to investigate the n-TiO2sedimentation behavior in aquatic environments. Results confirmed that IS, in which divalent cations may play an important role, was the dominating factor influencing the n-TiO2sedimentation behavior in aquatic environments.

The role of sodium chloride in the process of induction by lithium chloride in cells of the Rana pipiens gastrula

Development ◽  
1968 ◽  
Vol 19 (3) ◽  
pp. 387-396
Author(s):  
Lester G. Barth ◽  
Lucena J. Barth
Keyword(s):  
Sodium Chloride ◽  
Culture Medium ◽  
Rana Pipiens ◽  
Divalent Cations ◽  
Pigment Cells ◽  
Distilled Water ◽  
Sodium Ions ◽  
Monovalent Cations ◽  
High Concentration

A study of the effects of a series of monovalent cations, Li+, Na+ and K+, and a series of divalent cations, Mn2+, Ca2+ and Mg2+, upon small aggregates of cells taken from the presumptive epidermis of Rana pipiens gastrulae revealed that these ions induce nerve and pigment cells (Barth, 1965). The effectiveness of both series of ions as inductors was similar to their effects on decreasing the electrophoretic mobility of DNA as determined by Ross & Scruggs (1964). When it was found that sucrose in glass-distilled water also would induce nerve and pigment cells the role of ions as inductors came under closer scrutiny. A study of the nature of the induction by sucrose revealed that a relatively high concentration of sodium ions was necessary in the culture medium used after sucrose treatment (Barth, 1966).

Role of Divalent Cations on Deposition ofCryptosporidium parvumOocysts on Natural Organic Matter Surfaces

2010 ◽  
Vol 44 (12) ◽  
pp. 4519-4524 ◽  
Author(s):  
Dao Janjaroen ◽  
Yuanyuan Liu ◽  
Mark S. Kuhlenschmidt ◽  
Theresa B. Kuhlenschmidt ◽  
Thanh H. Nguyen
Keyword(s):  
Organic Matter ◽  
Natural Organic Matter ◽  
Divalent Cations

Cell-Glass Separation Depends on Salt Concentration and Valency: Measurements on Dictyostelium Amoebae by Finite Aperture Interferometry

1982 ◽  
Vol 54 (1) ◽  
pp. 299-310
Author(s):  
DAVID GINGELL ◽  
SHEILA VINCE
Keyword(s):  
Ionic Strength ◽  
Cell Membrane ◽  
Divalent Cations ◽  
Optical Measurements ◽  
Surface Glycoprotein ◽  
Monovalent Cations ◽  
Cell Surface Glycoprotein ◽  
Cellular Slime ◽  
Finite Aperture ◽  
Interacting Surfaces

Using pre-aggregation amoebae of the cellular slime mould Dictyostelium discoideum we have investigated the influence of cation concentration and valency on cell-glass separation. For computing the separation we used interference reflection microscopy and converted measured image irradiance to distance by finite aperture theory. Alterations in ionic strength caused virtually instantaneous reversible changes in the interference image due to changes in cell membrane-glass separation. In solutions containing monovalent cations, a change in ionic strength from 20 mM to 0.5 mM increased the separation of the plasmalemma from the glass by 60 nm. Divalent cations were better than monovalent cations at maintaining a small separation. Our results show that both divalent and trivalent cations adsorb to one or both of the interacting surfaces, in addition to acting as electrostatic double-layer counterions. The optical measurements also show that the cell membrane-glass gap is not reduced to zero by counterion screening; this is apparently due to the presence of a cell surface glycoprotein coat.

The role of divalent cations in the activation of the NADP+-specific isocitrate dehydrogenase from Pisum sativum L.

1977 ◽  
Vol 55 (9) ◽  
pp. 928-934 ◽  
Author(s):  
Robert J. Maloney ◽  
David T. Dennis
Keyword(s):  
Ionic Strength ◽  
Stability Constants ◽  
Isocitrate Dehydrogenase ◽  
Divalent Cations ◽  
Free Form ◽  
Saturation Kinetics ◽  
The Difference ◽  
The Stability ◽  
Kinetics Of

A divalent cation electrode was used to measure the stability constants (association constants) for the magnesium and manganese complexes of the substrates for the NADP+-specific isocitrate dehydrogenase (EC 1.1.1.42) from pea stems. At an ionic strength of 26.5 mM and at pH 7.4 the stability constants for the Mg2+–isocitrate and Mg2+–NADP+ complexes were 0.85 ± 0.2 and 0.43 ± 0.04 mM−1 respectively and for the Mn2+–isocitrate and Mn2+–NADP+ complexes they were 1.25 ± 0.07 and 0.75 ± 0.09 mM−1 respectively. At the same ionic strength but at pH 6.0 the Mg2+–NADPH and Mn2+–NADPH complexes had stability constants of 0.95 ± 0.23 and 1.79 ± 0.34 mM−1 respectively. Oxalosuccinate and α-ketoglutarate do not form measureable complexes under these conditions. Saturation kinetics of the enzyme with respect to isocitrate and metal ions are consistent with the metal–isocitrate complex being the substrate for the enzyme. NADP+ binds to the enzyme in the free form. Saturation kinetics of NADPH and Mn2+ indicate that the metal–NADPH complex is the substrate in the reverse reaction. In contrast the pig heart enzyme appears to bind free NADPH and Mn2+. A scheme for the reaction mechanism is presented and the difference between the reversibility of the NAD+ and NADP+ enzyme is discussed in relation to the stability of the NADH and NADPH metal complexes.

scholarly journals ON THE RECONSTITUTION OF THE CRYSTALLINE COMPONENTS OF THE SEA URCHIN FERTILIZATION MEMBRANE

1970 ◽  
Vol 45 (3) ◽  
pp. 606-614 ◽  
Author(s):  
Joseph Bryan
Keyword(s):  
Ionic Strength ◽  
Sea Urchin ◽  
Divalent Cations ◽  
Reducing Agents ◽  
Alkaline Ph ◽  
Mitotic Apparatus ◽  
Fertilization Membrane ◽  
Crystalline Component ◽  
Tubular Components

The characteristics of the reconstitution of a crystalline component of the sea urchin fertilization membrane are presented. The reassembly of large aggregates of cylindrical or tubular components is effected by the addition of calcium or other divalent cations. The reassembly requires a slightly alkaline pH and is little affected by increasing ionic strength. Reassembly is strongly inhibited by treatment with reducing agents such as dithiothreitol. The role of this protein in the formation of the fertilization membrane and its possible relation to the calcium-insoluble proteins of the mitotic apparatus are discussed.

The influence of aggregation on the redox chemistry of humic substances

2009 ◽  
Vol 6 (2) ◽  
pp. 178 ◽  
Author(s):  
Noel E. Palmer ◽  
Ray von Wandruszka
Keyword(s):  
Ionic Strength ◽  
Humic Substances ◽  
Reduction Potential ◽  
Divalent Cations ◽  
Redox Chemistry ◽  
Fulvic Acids ◽  
Monovalent Cations ◽  
Fluorescence Excitation ◽  
Reduction Potentials ◽  
Fluorescence Excitation Emission Matrices

Environmental context. The ability of humic substances (decaying plant and animal matter) to partake in redox reactions in the environment depends on the extent to which the various humic polymers aggregate in solution to form larger particles. This aggregation, in turn, is predicated on the solution conditions, especially ionic strength, the pH, and the types of cations present. Abstract. Aggregation and conformation play an important role in the aqueous redox chemistry of humic substances (HS). The reduction potentials of dissolved humic and fulvic acids vary with pH, ionic strength, and type of humate used, and depending on the solution conditions, they can abiotically reduce various species. Changes in HS reduction potential ranged from 60 to 140 mV on addition of divalent cations, whereas no significant changes were observed with equivalent additions of monovalent cations. Dynamic light scattering measurements showed that this behaviour paralleled the size changes obtained with humic aggregates under the same conditions. The effect was more pronounced at higher pH, where divalent cations caused a significant decrease in the average hydrodynamic radius, whereas monovalent cations did not. At pH 4, neither mono- nor divalent cations substantially affected aggregate sizes. Quinoid moieties, which are known to play an important role in the redox chemistry of HS, displayed fluorescence excitation–emission matrices with features related to changes in the reduction potential of HS. An increase in the reduction potential (Eh) induced by the addition of Ca2+, for instance, caused a red shift in the excitation–emission matrix maximum.

scholarly journals Role of divalent cations on DNA polymorphism under low ionic strength conditions

1986 ◽  
Vol 14 (12) ◽  
pp. 5099-5109 ◽  
Author(s):  
Sundaram Devarajan ◽  
Richard H. Shafer
Keyword(s):  
Ionic Strength ◽  
Dna Polymorphism ◽  
Divalent Cations ◽  
Low Ionic Strength

Protein–lipopolysaccharide interactions. 1. The reaction of lysozyme with Pseudomonas aeruginosa LPS

1978 ◽  
Vol 24 (2) ◽  
pp. 196-199 ◽  
Author(s):  
D. F. Day ◽  
M. L. Marceau-Day ◽  
J. M. Ingram
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Ionic Strength ◽  
Model System ◽  
Monovalent Cations ◽  
Low Speed ◽  
Initial Stage

Lysozyme (EC 3.2.1.17) complexes with extracted Pseudomonas aeruginosa LPS in two distinct stages. The initial stage does not produce turbidity detectable by nephelometry (measured as nephelos units (N) per time) but does permit low-speed sedimentation of the lysozyme–lipopolysaccharide (LPS) complex. This association is 100% disrupted by the action of 0.1 M Mg2+. Monovalent cations at equal ionic strength to the Mg2+ concentration used for these studies failed to alter significantly the lysozyme–LPS complex, indicating that the role of Mg2+ was not strictly an ionic one. The study of lysozyme–LPS complexes may provide a model system for investigating in vivo protein–LPS interactions.

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