Effect Of Divalent Ions Research Articles

Effects of divalent ions in surfactant flooding

The effect of divalent ions on the oil recovery efficacy of petroleum sulfonate surfactants was investigated. The oil recovery tests were conducted in unconsolidated model porous media composed of fine glass particles. It was found that tertiary recoveries effected by surfactant injection were consistently higher when the brine in the porous medium contained divalent ions. The results are explained by complete or partial pore blockage by precipitates formed when the petroleum sulfonate encounters divalent ions, which results in increased sweep efficiency. This conclusion is corroborated by the resukts of experiments in which a non-surfactant precipitate was formed in the porous medium during the flood.

Effect of corticosteroids on muscarinic receptors on cultured myocardial cells.

Rat myocardial cells in tissue culture were utilized to investigate modulation by corticosteroids on muscarinic receptor affinity. Competition binding experiments between tritiated quinuclidinyl benzilate and carbachol were performed on the muscarinic receptor both on whole cells and on a crude membrane preparation from cultured myocardial cells. Hydrocortisone was shown to promote a transition of the high affinity site of the muscarinic receptor towards super-high affinity. This was analogous with the effect of divalent ions. The affinity shift was detectable after 6 hr exposure to 0.1 microgram/ml of hydrocortisone in the tissue culture dishes but was abolished by concomitant incubation with a protein synthesis inhibitor (10 microM puromycin). The response on agonist binding of Gpp(NH)p in the presence of manganese ions was altered indicating that the adenylate cyclase-coupled muscarinic receptor nucleotide binding protein was modulated. No effects of corticosteroid exposure were noted on phosphatidyl inositol turnover.

Effect of salts on the entrapment of calf thymus DNA into liposomes

To correlate the conformational changes of DNA (Calf Thymus) with entrapment of DNA into lipsomes, the effect of ions(Na+, Mg++) on the entrapment of calf thymus DNA into liposomes was investigated. The effect of divalent ion(Mg++) on the structural changes of DNA indicated by decrease of observed ellipticity at 274 nm and nonspecific binding of DNA to lipid bilayers was greater than monovalent ion(Na+). But the efficiency of DNA encapsulated was not altered. These results show that entrapment of DNA into liposomes is not due to nonspecific binding and structural changes because of electrostatic forces but to mechanical capture of DNA by the internal aqueous space of liposomes although divalent ion contributes large structural changes and more nonspecific association of DNA with liposomes due to strong charges.

The effects of divalent ions on various aspects of Ca-activated K channels of goldfish hair cells

The effects of divalent ions on various aspects of Ca-activated K channels of goldfish hair cells

Effect of divalent ions in acrosome reaction induced by glycosamineglycans in porcine spermatozoa.

Magnesium, calcium, and zinc at the concentration of 10 microM are capable of inducing a "true" acrosome reaction in the pig spermatozoa judged by the criteria of the fusion of the acrosome and the plasmatic membrane at the anterior region or the sperm nucleus. The optimal percent of acrosome reaction reached by any of the ions tested as a whole was 50%. When glycosamineglycan sulfate (GAGs) plus 10 microM of Mg++, Ca++, or Zn++ was added, they reach to 70-80% of acrosome reaction. At the electrom microscope, thin sections taken from pig spermatozoa treated with ions, GAGs, or ion + GAGs under optimal experimental conditions revealed the same pattern of acrosomal reaction. Results suggest the important role that divalent cations play in general in the induction of the acrosome reaction and question the so-called essential role of calcium ions.

The Kinetics of Active K Transport by the Midgut of Lepidopteran Larvae: Effects of Divalent Ions

ABSTRACT The isolated midgut of lepidopteran larvae actively transports K from haemolymph to lumen, providing a model for K transport in insect secretory and excretory tissues (reviewed by Harvey, 1980). The dependence of this transport on extracellular K has been studied by several investigators. Recently, Zerahn (1982) estimated a value of 10 mM for Km in Hyalophora cecropia from his data and also from previous observations (Harvey & Zerahn, 1972), and obtained a value of 40 mM from data for Manduca sexta (Moffett, 1979). In the studies upon H. cecropia, the only cation present in the bathing solution was K; in the study upon M. sexta, 5 mM-Ca and 5 mM-Mg were also present as well as sufficient NaCl to maintain constant osmolarity. Although there may be slight innate differences in the transport kinetics of the two species, we show here that the reported differences can be accounted for by the presence or absence of divalent cations.

Binding of divalent cations with poly ( [formula omitted]) and their effects on the polypeptide conformation

The effects of divalent ions on fully charged poly(S- carboxymethyl- l-cysteine ) have been examined using circular dichroism for eight species: CuCl 2, CdCl 2, ZnCl 2, NiCl 2, CoCl 2, BaCl 2, CaCl 2, and MgCl 2. Five of them are effective inducers of β-form in the order: Cu 2+Cd 2+Zn 2+Ni 2+Co 2+, in media with no salt added. However, the other three ions (Ba 2+, Ca 2+ and Mg 2+), are not effective. Precipitation occurs when metal chlorides reach the vicinity of the equivalent point except for Ca 2+ and Mg 2+. Precipitation of the random coil form is slow, while that of the β-form is rapid. Addition of NcCl reduces the solubility of the β-form considerably. The pH value varies linearly with the logarithm of metal chloride concentration C M for Ba 2+, Ca 2+ and Mg 2+ ions, while nonlinear dependence of pH on log C M is found for Cu 2+, Ni 2+ and Co 2+ ions.

Modifying effects of divalent ions on the sulfhydryl content of normal and tumorous beet root tissue under thermal andγ-irradiation stress

Temperature and γ-irradiation stresses result in the loss of DTNB (5-5′ Dithionitrobenzoic acid) — reactive sulfhydryl groups in the TCA (trichloroacetic acid)-insoluble protein of normal and tumorous beet root tissue. Metal ions like Ca2+, Zn2+, and Pb2+ have been found to partially prevent the change of-SH quantity under stress conditions. An attempt has been made to correlate the observed loss of DTNB — reactive sulfhydryl content with the loss of membrane permeability under thermal and irradiation conditions.

Counter-ion dependence in salt-free, aqueous solutions of heparin

Chiroptical properties of heparin for various degrees of neutralization of the sulfate and carboxylic groups and for different counter-ions in salt-free aqueous solutions were investigated. Variations of optical rotation and ellipticity values at given wavelengths are compared to simultaneous pH and viscosity changes observed during the neutralization of heparin by sodium and calcium hydroxide. For Na +, variations of ellipticity at 210 nm are related to acid—base properties of uronic carboxylic groups. C.d. characteristics found for alkaline-earth counter-ions (Mg 2+, Ca 2+ and Ba 2+), as compared to Na +, are assigned to effects of divalent ions on the ionization behavior of carboxylic groups. Among the divalent counter-ions considered, Ca 2+ gave the strongest interaction with the heparin polyanion, but no specific complex formation was observed. O.r.d. and c.d. data are discussed on the basis of a randomly coiled structure for macromolecules composed of rigid, heterocyclic repeating-units that are independent of each other in so far as electronic transitions of chromophore groups contributing to optical activity are concerned.

Plant Growth Hormones: Internal Control Points

Examples of control points involved in regulation of the availability or action of certain plant hormones are presented. The effects of divalent ions, environmental factors, and other hormones on hormone synthesis, release, or action are illustrated The role of gibberellins (GAs) in promoting cell enlargement and division in intact plants is analyzed in view of the paradoxical inhibition of cell division in tissue and suspension culture by GA3. The importance of the intact subapical region as a target site is underlined, but the possibility is raised that GAs play only an indirect role in regulation of cell multiplication at this site. The cereal aleurone layer as a target site for GA action is discussed with the objective of identifying the primary control points. Analysis of existing information most favors a role for GAs in (1) stimulating synthesis of mRNA, and (2) intervening in transcription or translation. There is a paucity of evidence for specific binding sites for plant hormones. With the except...

Effects of divalent ions on vesicle-vesicle fusion studied by a new luminescence assay for fusion

Summary. A new assay has been developed for vesicle-vesicle fusion based upon the mixing of intravesicular contents of two sets of vesicles. Purified firefly luciferase and MgC12 were incorporated into one set of vesicles (LV) and ATP into the other (AV). Vesicles were prepared from soybean phospholipids. The luminescence that resulted from hydrolysis of ATP by luciferase was measured to determine the extent of mixing of the intravesicular contents. In the absence of divalent ions, incubation of a mixture of LV and AV did not produce luminescence. However, if Ca + § or other divalent ions were present at miltimolar concentrations, luminescence occurred. The luminescence did not result from extravesicular reaction of vesicle contents that had leaked into the medium. Instead, luminescence resulted from the mixing of intravesicular spaces of AV and LV in fused vesicles. Optical density changes and negative stain electron microscopy indicated that Ca § + induced extensive aggregation of vesicles. However, quantitation of the maximum possible luminescence indicates that only a small percentage (less than 1%) of the vesicles actually fused in a fusion experiment. Addition of EDTA to chelate Ca ++ after luminescence had been induced resulted in a two- to threefold increase in light emission which then rapidly decayed. These results suggest that the sudden removal of Ca § § caused a transient increase in fusion after which subsequent fusion was inhibited. It was also found that the vesicles were relatively stable to hypotonic solutions.

The influence of surface charge on the kinetics of ion-translocation across biological membranes

Rate equations have been developed which describe the concentration dependence for ion-translocation across charged membranes for those cases in which the translocation process can be considered to be formally equivalent with an enzymic process of a Michaelis-Menten type. We have limited ourselves to those cases in which the ion-translocational step through the membrane is electroneutral. In addition it is assumed that the sites on the membrane involved in the ion-translocation process can not move through the membrane when these sites are not occupied by ions. It is shown that in general deviations from Michaelis-Menten kinetics may be expected. In case of monovalent ion-translocation across oppositely charged membranes apparent negative homotrope cooperative effects may occur, whereas for ion-translocation across equally charged membranes apparent positive homotrope cooperative effects may be found. When the bulk aqueous phase also contains polyvalent ions both types of effects may occur both in the case of ion-translocation across oppositely charged membranes as well as with ion-translocation across a membrane of which the sign of the surface charge is the same as that of the ion translocated. Under limited conditions, also apparent single Michaelis-Menten kinetics may be observed. In these cases, however, the apparent K m generally is no linear function of the concentration of a competing ion. It is shown that even when an ion does not bind to the translocation sites the K m is affected by increasing concentrations of this ion, a phenomenon which is not expected when the membrane is not charged. The effects of divalent ions, added to the bulk aqueous phase as 1-1-electrolytes, upon the K m are discussed in connection with in literature reported effects of Ca ++ upon the rate of uptake of several monovalent ions into plant cells.

The role of lipids in the transfer of ATP and cAMP into organic media: The effects of metallic salts, basic proteins, and atractyloside

The present paper studies the effect of several lipids (charged and uncharged), metal ions, atractyloside, protein, and pH on the solubility characteristics of ATP and cAMP in organic solvents, mainly by partition experiments, using labeled nucleotides. If amphipathic lipids are absent from the system, these highly hydrophilic nucleotides cannot be transferred into the organic solvents in which they are completely insoluble. The effectiveness of divalent metal ions in transferring ATP into the organic solvents is in the order Cu ++ > Ca ++ > Mg ++. This effectiveness of divalent ions is reduced by higher concentrations of univalent cations. When positive charges are incorporated in the lipid system by adding eicosanyl trimethylammonium bromide, stearoyl choline chloride, or basic protein (protamine), a large amount of nucleotide could be transferred into the organic solvents, but addition of CaCl 2 reduces this effect. A negatively charged lipid, cholesterol, or atractyloside is not effective at all. These observations have been explained mainly in terms of electrostatic interaction, though van der Waals forces should also be taken into account. Our findings could be of significance in understanding a mechanism whereby polar molecules such as nucleotides can move across the potential energy barrier of the lipid membrane.

Preillumination effects on chloroplast structure and photochemical activity

The effects of in vivo preillumination with short wavelength red light (647 nm) and long wavelength red light (710 nm) on fluorescence and photochemical characteristics of algal and higher plant chloroplasts were analyzed and data are correlated to previous studies of divalent ion effects on isolated chloroplasts. The 647 nm light increased the sensitization of photosystem I as determined from fluorescence emission at low temperature, decreased room temperature variable yield fluorescence, decreased the sigmoidal aspect of fluorescence rise, and increased the rate of photosystem I reactions measured in low intensity 647 nm light. DCMU blocked 647 preillumination effects. These data are consistent with a previous suggestion that preillumination effects on chloroplast fluorescence are related to light-induced ionic redistributions in the organelle. Structural organization of pea chloroplasts preilluminated with either 647 or 710 nm light were not significantly different with respect to the extent of grana stacking observed. The differences between membrane structural reorganization observed after preillumination and those observed with chloroplasts in the presence or absence of salts is discussed.

Effect of divalent ions on pigeon kidney pyruvate carboxylase

Effect of divalent ions on pigeon kidney pyruvate carboxylase

Measurements of cell adhesion:II Quantitative study of the effect of divalent ions on cell adhesion

ABSTRACT The forces of interaction found for 5-day chick limb-bud cells in media containing different divalent ions (magnesium, calcium, strontium or barium) show that the cells are most adhesive in the presence of magnesium ions, then calcium and strontium, then barium. When magnesium and calcium ions are present together at similar concentrations the calcium ions modify the action of the magnesium ions. The importance of magnesium ions in cell adhesion is discussed.

Dielectric properties of polyelectrolytes. III. Effect of divalent cations on dielectric increment of polyacids

AbstractDielectric dispersion of polyacrylic acid (PAA) and polystyrene sulfonic acid (PSS) was measured in the presence of divalent cations. Effects of divalent ions were studied by neutralization with varying ratios of sodium hydroxide and divalent base concentration, addition of salts of divalent cations, and neutralization with divalent bases only. Two dispersion regions were observed in all cases, i.e., low‐frequency dispersion (102–104 Hz) and high‐frequency dispersion (105–106 Hz). The dielectric increment increases in the presence of sodium and alkaline earth metal ions together, but not with sodium and transition metal ions. This is due to the increment of low‐frequency dispersion and is attributable to the fluctuation of bound counterions which is explained by our theory previously reported.1 In the case of PAA neutralized with large fractions of divalent ions, or with divalent ions only, the increment is very small because of reduction of the fluctuation by interaction between bound ions at the neighboring sites and reduction of the effective length of polyion probably due to chelation by divalent ions. There are some differences among the effects of Mg++, Ca++, and Ba++ on dielectric increment which may result from affinity or chelating ability of these ions.

Effects of divalent ions and drugs on synaptic transmission in phasic electroreceptors in a mormyrid fish.

We recorded impulses in afferent nerve fibers innervating two kinds of phasic electroreceptors in a mormyrid fish. We used an isolated preparation of skin, receptors, and sensory nerves to estimate synaptic delays, and to change solution in contact with the receptor-nerve synapse. The minimum delays between stimuli and sensory nerve responses, which must be slightly larger than synaptic delays, are about 0.7 msec in medium receptors and about 0.25 msec in large receptors. This result supports previous suggestions that transmission is chemically mediated in medium receptors and electrically mediated in large receptors. Furthermore, Mg(+2) depresses synaptic transmission in medium receptors, and has little effect on transmission in large receptors. A complex dependence of response on both Mg(+2) and Ca(+2) masks divalent ion dependence of transmission, but a large excess of Mg(+2) cannot completely block transmission in medium electroreceptors. L-glutamate, and not cholinergic drugs, produces a sequence of excitation and depression of medium receptor response which indicates that a similar chemical is the transmitter in the afferent synapse.

The effect of divalent ions on the isolation of proteins from rat liver nucleoprotein

The nature and quantity of acid-soluble proteins separated from rat liver nucleoprotein is greatly dependent upon the presence of divalent metal ions. In the absence of these ions, and particularly in the presence of EDTA, low yields of protein are obtained because of greater solubility of the nuclear contents. Moreover, the use of EDTA selectively removes the “arginine-rich” proteins from the nucleoprotein pellet, so that eventual protein fractionation results in relatively extensive retention of “arginine-poor” proteins. The use of divalent metal ions (Mg 2+, Mn 2+) produces similar fractionation patterns. The use of NaCl as the electrolyte allows the isolation of some arginine-rich protein, but in very low yield when compared to the preparations using divalent ions. Thus, ionic strength is a minor factor in the extraction of the arginine-rich proteins from such nuclei, but the presence of divalent metal ions is the most important requirement. Evidently these metal ions exercise an important role in maintaining the structural integrity of arginine-rich nucleoproteins in the nuclei.

The effects of divalent cations on the glycerinated smooth muscle of guinea-pig taenia coli.

Using glycerinated taenia coli of the guinea-pig, the effects of divalent ions (Ca, Mg, Mn and Zn) on the contractile system of the smooth muscle were studied. Mg ion is essential for ATP contraction of glycerinated smooth muscle. Mn ion can substitute perfectly for Mg ion, but Ca ion cannot. The initiation of ATP-contraction in the presence of Mn ion is suppressed by addition of higher concentra-tion of Ca ion. Zn depresses the initiation of ATP-contraction, but it is ineffective in relaxing the ATP-contraction. The present results imply that Zn ion depresses the initiation of contraction by blocking all stages of contractile process in the smooth muscle.