Monovalent Salt Concentration Research Articles

The modification of the reconstituted sarcoplasmic ATPase by monovalent cations.

The effects of monovalent cations on the calcium‐dependent ATPase activity of lipid‐depleted and reconstituted sarcoplasmic membranes have been investigated. The calcium‐dependent ATPase activity of sarcoplasmic membranes whose lipid components have been modified are significantly more sensitive to activating and/or inhibitory effects of monovalent cations than that of native sarcoplasmic membranes. Activating and inhibitory effects of the applied monovalent ions depend on the concentration of ionized calcium in the medium. In dilute calcium media ([Caz+] = 0.8 μM) modified ATPase preparations are always inhibited by high concentrations (>0.2M) of monovalent salts. Conversely, in concentrated calcium media ([Ca2+] = 0.18 mM) modified ATPase preparations are in most cases activated by increasing (>0.2 M) concentrations of monovalent salts. Activating effects of the monovalent ions decrease and specific inhibitory effects increase in the order K+, Ria+, Rb+, Cs+, Li+. This order corresponds to that found if the ions are arranged according to the increasing distance between potassium and the respective ion on the hydration enthalpy scale. The results have been discussed in relation to a specific competition between calcium ions bound to the inhibitory side at the inner surface of the sarcoplasmic membranes and the applied monovalent ions.

Photoreactions of chloroplasts in a glycine medium.

The rate of photoinduced electron transport in a medium containing glycine as the major salt was very low. It was dramatically increased by low concentrations of monovalent salts (2–4 mM) to rates typical of uncoupled systems. Further increase in salt concentration (beyond 15–20 mM) cause a sharp decrease back to “coupled” values. Salts of divalent ions, like Mg2+ were even more effective in the “recoupling” process (0.1 mM).When low amounts of Mg2+, phosphate and ADP were added to the glycine medium, photophosphorylation proceeded initially at high rates but stopped after a certain amount of ATP was accumulated. This effect was traced to a complete inhibition by the ATP formed of any further phosphorylation. The concentration of ATP needed to inhibit increased sharply with an increase of the salt concentration in the medium. ADP exhibited a similar inhibitory effect but higher concentrations were required.At concentrations where ATP inhibited phosphorylation, proton uptake was not affected.

Extraction partielle des proteines de ribosomes de foie de rat par differents cations monovalents: Proprietes des particules obtenues

Partial extraction of proteins from rat liver ribosomes by different monovalent cations. Properties of the core particles 1. Rat liver ribosomes were dissociated into subunits by centrifugation through a sucrose layer containing increasing concentrations of various monovalent cation salts. Poly U-directed polyphenylalanine synthesis by subunits was dependent on the nature and concentration of monovalent cations. Subunits prepared with the following salts: RbCl, KCl, NH 4Cl and NaCl had maximum activity when 0.3 M salts were used. The activity of the subunits obtained with 0.3 M RbCl was particularly high. Then activity decreased more or less rapidly according to monovalent cation, when the salt concentration was raised from 0.3 to 0.7 M. The activity of the subunits prepared with other salts (LiCl, CsCl and thallium acetate) continuously decreased with salt concentration without any maximum. When ribosomes were treated with salts at 25° instead of 4°, similar results were obtained, except for NaCl that behaved like the last mentioned salts. 2. Subunits prepared with 0.5–0.7 M monovalent cation salts sedimented in a sucrose gradient a little slower than those obtained with 0.3 M salts or native subunits. In a MgCl 2-rich buffer ability of subunits to reassociate varied in the same manner as activity: it was dependent on the monovalent cation used for preparing them, but diminished in every case when salt concentration was raised beyond 0.3 M. 3. Subunits prepared with 0.5 M salts, unlike the one prepared with 0.3 M salts, had a density and a chemical composition markedly different from that of control ribosomes. They had lost between 15 and 36 % of their proteins and then should be considered as incomplete subunits or core particles. The amount of proteins that were extracted depended on the monovalent cation used. The salts could be classified according to their ability to extract ribosomal proteins as follows: NaCl > LiCl > KCl, RbCl > NH 4Cl, CsCl. Thallium acetate represented a special case for extracting 27 % proteins even at 0.3 M concentration. 4. Extracted proteins and particle proteins were analysed by polyacrylamide gel electrophoresis. In every case it was observed that salts preferentially extracted some proteins, which were acidic or had relatively high molecular weight. Proteins of subribosomal particles prepared with various salts, when compared together, were found to be not exactly the same. 5. Extracted proteins, when added back to the corresponding core particles, greatly increased the ability of particles to reassociate. The reconstituted material had the same density as control ribosomes. However, activity was not restored when inactive core particles were used for these experiments.

Disaggregation of slime mold pseudoplasmodia using EDTA and various proteolytic enzymes

Effects of EDTA and various proteolytic enzymes on disaggregation of the pseudoplasmodium (slug) of the cellular slime mold Dictyostelium discoideum were studied under diverse conditions. EDTA alone was ineffective in disaggregation, but became effective when concentrations of monovalent salts in the solution were increased to a certain level. Its effectiveness also depended on the presence of salts in the agar on which the slug had been incubated. Although various proteolytic enzymes were ineffective when used alone, all became effective in the presence of 2,3, dimercapto-1-propanol (BAL). The presence of monovalent salts, in both disaggregating and culture media, also promoted disaggregation by proteolytic enzymes, as it did in the case of disaggregation by EDTA. Disaggregation by proteolytic enzymes, however, was more complete than it was using EDTA. Pronase plus BAL was most effective and did not require the presence of salt for complete disaggregation. After they were wahed, all cells disaggregated were viable and carried out normal morphogenesis. Mercaptoethanol, but not cysteine, had an effect substitutable for the BAL effect on disaggregation. Possible mechanisms by which NACl and BAL effect disaggregation by EDTA and proteolytic enzymes are discussed.

Interaction des Ions Métalliques avec le DNA. II. Adsorption préférentielle de l'Ion césium par les Acides nucléiques

AbstractPreferential adsorption of cations occurs in the solvated shell surrounding polyanions, especially polynucleotides and nucleic acids. The solvation parameter Γ is determined from sedimentation coefficients which are considered as pienometric determinations of the specific volume of the sample. By comparing two identical concentrations (0.1M) of monovalent salts, NaCl and CsCl, and using the model of DNA described in the preceding paper, one can relate the ratio SCs/SNa to solvation parameters ΓCs, and ΓNa.On the other hand, Γ can be related to the difference of energy W, between cation and water, to be extracted from the solution and placed in the vicinity of the polyanion. One finds generally a preferential solvation of the polarizable caesium ion by means of London–van der Waals interactions with bases. With reasonable assumptions, an estimate of W can be made, and the predicted value of Γ can be compared to the experimental one. An average of six sites is found around each base in a single‐stranded polymer, but‐only one in the double‐stranded structure. The amount of secondary structure can thus be estimated from the simple measurement of the ratio of two sediment constants.

Irreversible Heat Inactivation of Transfer Ribonucleic Acids

Abstract Heat inactivation of transfer ribonucleic acids at 90° in a solvent of neutral pH and moderate concentration of monovalent salts leads to a 63% loss (1 hit per molecule) of three different biological functions in about 10 hours. Addition of Mg++ increases the rate of inactivation 20-fold. While chain scission is shown to be the most important mechanism of inactivation in the presence of Mg++, it accounts for only 20 to 50% of the inactivation in the absence of Mg++. Whereas depurination, deamination, and aggregation have been ruled out as additional important means of heat inactivation in the absence of Mg++, the destruction of 5,6-dihydrouridylic acid residues appears to be a quantitatively significant one.

Effect of Osmotic Shock and Low Salt Concentration on Survival and Density of Bacteriophages T4B and T4Bo 1

Measurements of survival and buoyant densities of bacteriophages T4B, T4Bo(1), and T4D have demonstrated the following: (a) After suspension in a concentrated salt solution, T4B and T4D are sensitive both to osmotic shock and to subsequent exposure to low monovalent salt concentrations. (b) Sensitivity of T4B to dilution from a concentrated salt solution is dependent on dilution rate, that of T4D is less dependent, and that of T4Bo(1) is independent. (c) Sensitivity of all three phages to low salt concentrations depends on initial salt concentrations to a variable extent. (d) Density gradient profiles indicate that nearly half of osmotically shocked T4B retain their DNA. Similar analysis demonstrates that few, if any, T4Bo(1) lose DNA when subjected to a treatment causing 90% loss of infectivity. (e) The effective buoyant densities of T4B and T4Bo(1) depend significantly on the dilution treatments to which the phages are subjected prior to centrifugation in CsCl gradients. These data are explicable in terms of the different relative permeabilities of the phages to water and solutes, and of alterations in the counterion distribution surrounding the DNA within the phage heads.

Size heterogeneity of T2 messenger RNA

The size distribution of 14C-labeled T2 mRNA molecules carefully isolated to avoid enzymic degradation was studied using sucrose density-gradient centrifugation. A heterogeneous distribution of sedimentation coefficients ranging from 10 s to 30 s was observed. The most common component sedimented about 14 s to 16 s, and approximately half the molecules sedimented faster than 16 s. No major sedimentation difference was found between T2 mRNA molecules synthesized at various intervals throughout the viral growth cycle. In the presence of high concentrations (> 0·5 M) of monovalent salts, mRNA molecules reversibly combine with ribosomal RNA chains to form rapidly sedimenting aggregates. The aggregation induced by high salt concentration also occurs during elution of labeled mRNA from methylated serum albumin columns. The high (> 0·5 M) NaCl concentrations needed for elution can cause the mRNA molecules to complex reversibly with the rRNA molecules. As a result, the mRNA molecules come off the columns later than they would in the absence of ribosomal RNA.

The G - F equilibrium in actin solutions under various conditions

The reversible establishment of equilibrium states in actin solutions, has been investigated under various solvent conditions. In the equilibrium state F-actins coexist with G-actins, the concentration of the latter being determined by the solvent condition. The physical feature of the G - F equilibrium is expressed as a kind of condensation phenomenon. The phase diagram of the equilibrium has been obtained over wide ranges of solvent conditions, i.e., pH, concentrations of monovalent salts, magnesium, calcium, nucleotides, and organic solvents, and temperature. It has been found that the difference in the effects on the equilibrium of magnesium and calcium increases with increasing concentration of monovalent salts, with increasing pH, and with decreasing temperature. A parallelism has been found between the equilibrium level and the G - F transformation rate and, within the range of the solvent condition here examined, the structure of F-actin is little changed by the solvent condition.

THE ASSESSMENT OF RELATIVE BACTERICIDAL ACTIVITY AMONG CERTAIN PHENOLS BY A PHYSICAL METHOD

SUMMARY: The addition of phenol, various alkyl phenols, or CTAB to a suspension of E. coli in distilled water caused the optical density to increase, the change being more marked as the concentration of a given compound was raised. Families of curves of similar shape were obtained with all the compounds when optical density was plotted against time for different concentrations, and figures expressing the activity relative to that of 1·2% phenol were obtained by dividing the concentration which produced the same curve as that concentration of phenol, into 1·2. These figures were very similar to those obtained for the bactericidal effects of the compounds relative to 1·2% phenol, using an ‘end‐point’ method.The presence of the chlorides of mono‐ and divalent metals at 10−4 M, or of the sulphates of trivalent metals at 10−5 M, did not affect the turbidity reaction, but higher concentrations of monovalent metal salts, e.g. 2 × 10−2 M phosphate buffer (potassium) at pH 6·7, markedly retarded the change due to phenol. That concentration of the buffer also greatly reduced the bactericidal activity of 1·2% phenol. Much of the turbidity increase, however, occurred after all the cells of the suspensions had been killed, with phenol concentrations over 1·0%.

The effect of monovalent salts on the acceleration of myosin B ATPase by magnesium

The effects of magnesium and of calcium on the ATPase activity of myosin B have been investigated in the presence of a range of concentrations of monovalent salts ([Me +A −]). At zero or low [Me +A −] MgCl 2 increases the ATPase activity; at intermediary [Me +A −] low concentrations of MgCl 2 depress activity while high concentrations of MgCl 2 accelerate slightly; at high [Me +A −], high concentrations of MgCl 2 have a small accelerative tendency. The rise in activity at high [Me +A −] and the second rise at intermediate [Me +A −] are caused by 10 −3 M MgCl 2 and have not been observed in other investigations. The inhibition caused by magnesium is not clearly due to dissociation of myosin B into actin and myosin A. The effects of salts on the Mg-effect does not appear to be one of ionic strength because the kind of salt has an effect. The response of myosin B ATPase is inconsistent from preparation to preparation. Differences in myosin B preparations are shown. The possibility of covalent and electrostatic bonding of magnesium to myosin is discussed. The effects of magnesium on the ATPase of glycerol-extracted muscle are not as complex as on that of myosin B. Ammonium chloride in the absence of other metallic cations increases the activity of myosin B ATPase.