Function Of NaCl Concentration Research Articles

Light scattering of micellar and polyelectrolyte solutions: influence of added salt

Static and dynamic light-scattering experiments have been carried out in order to study two polyelectrolyte systems: System A consists of globular and rigid macroparticles such as micelles and system B contains flexible and anisotropic polymer chains. The dependence of the scattered intensity and mutual diffusion coefficient on concentration of polyelectrolyte-salt solutions is analyzed in terms of theoretical models (pair repulsion potential and Debye-Huckel approximation). Good fits are obtained at low salt concentration for tetradecyltrimethylammonium bromide series, sodium dodecyl sulfate, and tetradecyltrialkylammonium bromide micelle solutions with the virial development and the noninstantaneous diffusivity of small ions. The ionization degree is independent of salt concentration, but it is very sensitive to the size of ionic head groups. The static and dynamic properties of flexible polyelectrolyte-salt solutions have been reported (system B). From the q dependence of scattered intensity, it is deduced that chains have a “coil” conformation in the presence of excess of salt. The ionic strength dependence of the effective diffusion coefficient of sodium polystyrene sulfonate (NaPSS) is investigated as a function of NaCl concentration. The results indicate a splitting in the relaxation times which depends on the ratio C p C s where C p and C s are the polyion and added salt concentrations, respectively. At last, we present some comments on the different properties of these two charged macromolecule solutions (A and B). The role of counterions is discussed. In particular the counterion effects seriously modify the dynamics of polyions in low salt concentration.

Measurement of colloid mobility by laser doppler electrophoresis: the effect of salt concentration on particle mobility

Laser Doppler electrophoresis (LDE) possesses distinct advantages over conventional electrophoretic methods. The apparatus described here incorporates the reference beam approach, square-wave electrode current, and frequency domain processing. The experiment employs a photodetector in place of a PMT and electronics designed to shape and symmetrize the electrode current instead of the voltage waveform. LDE was used to measure mobility as a function of NaCl concentration c over the range 2 × 10 −4 to 2 × 10 −2 mole dm −3 for a series of different strong acid latexes. In light of these data various theories of the double layer at the colloid-aqueous interface were examined, with particular importance attached to the maximum exhibited when the mobility of such latexes is plotted against salt concentration. The simple Gouy-Chapman theory relates well to the trend at high c, but the theory must be adapted, in one of several ways examined in this paper, in order to explain the low and medium c trend. Weak acid latexes have a different dependence on c and must be explained by appeal to other models.

During B-Z transition there is no large scale breakage of Watson-Crick base pairs. A direct demonstration using 500 MHz 1H NMR spectroscopy.

Monitoring of the Watson-Crick GNH1 proton in poly(dG-dC).poly(dG-dC) at 500 MHz in 90% H2O:10% D2O at 30 degrees C as a function of NaCl concentration (1.5 to 3.6 M), demonstrates that the bases retain Watson-Crick pairing throughout the transition. This observation unequivocally demonstrates that during the B-Z transition there is no large scale and detectable base pair opening and that macroscopically the phenomenon can be described as a direct helix to helix transition. We present frame by frame, an energetically sound stereodynamical trajectory for this transfiguration from right-handed B-DNA to left-handed Z-DNA.

Alterations in the toxicity of cis-Dichlorodiammineplatinum-II and in tissue localization of platinum as a function of NaCl concentration in the vehicle of administration

The lethality to mice of the anticancer drug cis-dichlorodiammineplatinum-II (cisPt) was greatly reduced when the drug was dissolved in hyperonic (4.5%) NaCl relative to preparation in distilled water (DW). Concomitant administration of 4.5% NaCl and cisPt prepared in DW failed to protect mice against cisPt toxicity. When other chloride salts were used as vehicles, partial protection was observed and when NaI was used as a vehicle, nearly complete protection was obtained. Similarly in rats, toxicity was reduced with the hypertonic vehicle when lethality, clinical chemistry, or histopathology criteria were evaluated. In vitro and in vivo binding to plasma proteins was greater with the DW vehicle. Tissue Pt levels were less and decayed more rapidly with the hypertonic NaCl vehicle. Antitumor effectiveness of cisPt was not altered when 4.5% NaCl was utilized as the vehicle. A postulated explanation for these results is a shift in the cisPt aquation reaction due to the high concentration of chloride ions in the vehicle.

Flow dichroism of T7 DNA as a function of salt concentration.

AbstractMeasurements have been made on the flow dichroism of T7 DNA as a function of NaCl concentration. In high salt, our results are compatible with an optical factor of −1.4 and a persistence length of 470 Å. The former is in agreement with expectations from the x‐ray diffraction structure of fibrous B–DNA, and the latter is in the midrange of recent determinations. As salt concentration is decreased, the persistence length increases. The relation of our study to other recent investigations and with current theories of the electrostatic contribution to persistence length is discussed. We note that the separation of the electrostatic expansion factor into long‐ and short‐range effects is somewhat arbitrary and might affect the interpretation of different experimental results in different ways. Finally, our hydrodynamic factors are consistent with a chain which is partially free‐draining. This goes against the traditional interpretation but is in agreement with two recent observations.

Salt seeking by means of food and fluid selection in adrenalectomized rats

An experiment involving several changes in the salt content of food and solutions investigated the generality of salt-seeking behavior in adrenalectomized rats. Salt-solution intake varied as a function of NaCl concentration. The intake of sodium is relatively unaffected by the concentration of NaCl in the food as long as NaCl in solution is available. But when the salt solution is removed, salt seeking and sodium regulation takes place by way of salt in the food.

Characterization of poly(ether/amide) and poly(ether/urea) thin film composite membranes by transport coefficients

Several thin-film composite membrane systems, Poly(ether/amide) and Poly-ether/urea) have been characterized in hyperfiltration and dialysis-osmosis experiments. Using the phenomenological relationships of the thermodynamics of irreversible processes, the hydrodynamic permeability, l p, the osmotic permeability, l π, the asymptotic salt rejection, r ∞ , and the reflection coefficient, σ, have been determined as functions of NaCl concentration at 25δC. All membranes yielded large values of r ∞ even at brine concentrations of 0.5 M NaCl and a small variation of salt rejection r, with pressure corresponding to a ratio of l π/l π not much larger than r ∞ 2. The reflection coefficients received from dialysis-osmosis experiments differ substantially from the corresponding values of the asymptotic salt rejection, r ∞. A comparison between the transport coefficients of these thin-film composite membranes and the transport coefficients of some asymmetric cellulose acetate membranes show that the thin-film composite membranes behave much more like a semipermeable membrane.

Nuclear magnetic resonance quadrupole relaxation study of chloride binding to hemoglobin abruzzo ( α2Aβ2143 His → Arg)

Chloride binding to the carbon monoxide derivative of hemoglobin Abruzzo ( α 2 A β 2 143 His → Arg) has been measured as a function of NaCl concentration and pH. The results suggest that the CO derivative of hemoglobin Abruzzo has at least two classes of chloride binding sites, one of high, the other of low affinity, just like hemoglobin A. The pH profile shows distinct features with respect to hemoglobin A, which have been interpreted in terms of modifications of strong chloride binding site(s). This result is of particular interest in view of the involvement of His β-143 in organic phosphate binding.

The surface charge and double layers of thin lipid films formed from neutral lipids

1. 1. The specific capacitance ( C m ) of thin lipid films formed from dispersions of glyceryl-1-monoolein in n- decane has been measured as function of NaCl concentration in the presence and absence of 2,4-dinitrophenol in order to examine the double layers and surface charge of films formed from neutral lipids. 2. 2. When 2,4-dinitrophenol is absent, plots of C m against NaCl concentration ( 10 −4−10 −1 M ) accurately fit curves predicted by double layer theory (Everitt, C. T. and Haydon, D. A. (1968) J. Theor. Biol. 18, 371–379) assuming an adsorbed surface charge of 0.769·10 −7 C/cm 2 corresponding to 2.08·10 4 A 2/charge. 3. 3. In the presence of 10 −4 M 2,4-dinitrophenol, an adequate fit of the dtata to the theoretical curves is obtained if the surface charge is assumed to be 2.53·10 −7 C/cm 2 corresponding to 6.32·10 3 A 2/charge. This finding supports the hypothesis of S. McLaughlin ( J. Membrane Biol. 9 (1972) 361–372) that 2,4-dinitrophenol adsorbs to the surface of neutral bilayers and imparts a negative charge. 4. 4. The geometrical capacitance ( C g ) of the bilayer in the absence of 2,4-dinitrophenol is 0.4057±0.0067 (S.D.) μF/cm 2 if the NaCl concentration is 10 −1 M or less. C g=0.4348±0.0071 (S.D.) μF/cm 2 in 1 M NaCl. This increase is probably a result of either a real or apparent decrease in hydrocarbon thickness of approx. 3 Å. In the presence of 10 −4 M 2,4-dinitrophenol, C g=0.3982±0.119 (S.D.) μF/cm 2 which is not statistically different from the value obtained in the absence of 2,4-dinitrophenol.

Intermittent reinforcement and salt arousal of thirst in rats

Sated rats, previously trained to leverpress for H2O reinforcement on continuous or variable-interval (10-sec or 60-sec) schedules, were given NaCl injections and tested for leverpressing. Under all schedules, responding was an inverted U function of NaCl concentration (0.15M to 3.0M). However, NaCl thirst produced relatively little change in behavior under the VI 60-sec schedule.

Virial coefficients of protein solutions

An osmometer capable of measuring protein osmotic pressures up to 100 cms. of mercury pressure has been described. The principle of the osmometer is to set a given pressure and to permit the protein concentration to equilibrate with the pressure. The higher virial osmotic coefficients of egg albumin in various electrolytes and in 1 m urea as well as a function of NaCl concentration are reported. The virial coefficients of bovine serum albumin and of bovine methemoglobin in 1 m NaCl are also given. It appears that the primary cause for the departure of the osmotic pressure from ideality is due to the covolumes of the proteins.

Apparent Dissociation Constant of Phenol Red as Determined by Spectrophotometry and by Visual Colorimetry

Abstract The apparent pK' of phenol red was determined in buffered NaCl solutions of known composition at 25° and 37°, by both spectrophotometric and visual colorimetric measurement of the concentration ratios of the alkaline to acid form of the indicator. A small but statistically significant difference was obtained by the two procedures. The pK' values obtained in 0.15M NaCl spectrophotometrically (7.67 at 25° and 7.57 at 37°) were approximately 0.03 unit lower than those obtained colorimetrically. Measurements made as a function of NaCl concentration at 25° were in accord with the Debye-Hückel theory. Small variation was observed between solutions buffered with phosphate or tris at the higher NaCl concentrations. The results indicate that in addition to ionic strength and temperature, variations in method of measurement and in the source of the preparation are important factors in the determination and use of pK' values for phenol red. Attention is called to the pertinence of these results to the measurement of blood pH by colorimetric and spectrophotometric methods.

Critical phenomena in aqueous solutions of long-chain quaternary ammonium salts

Solutions of hyamine 1622 (di-isobutyl phenoxy ethoxy ethyl dimethyl benzyl ammonium chloride) at concentrations above the critical micelle concentration have been studied as a function of NaCl concentration and temperature. At a given temperature there is a critical NaCl concentration above which the system separates into two layers; the top layer is practically free of the quaternary ammonium salt and the bottom layer shows the characteristics of an oil. The volume of the bottom layer decreases with increasing NaCl concentration. Before the onset of the two-phase separation, the turbidity and the dissymmetry of light scattering increases with increasing NaCl concentration. Small temperature changes produce a marked change in the stability of the bottom layer. In the immediate neighborhood of the critical temperature the system exhibits a marked opalescence. The experimental results can be explained in terms of current concepts of critical solution phenomena where NaCl alters the interactions between the micelles of the quaternary ammonium salt. The details of the interactions are given qualitatively by the theory of Verwey and Overbeek.

The Antigen-Antibody Reaction

Summary A quantitative study of the precipitin reaction has been made as a function of NaCl concentration. The system used was chicken ovalbumin and the homologous rabbit antibody separated into its eu- and pseudoglobulin fractions and the same antibody fractions and duck ovalbumin as the heterologous system. Using pseudoglobulin antibody, it was shown that in the virtual absence of salt the precipitin reaction not only persists but gives larger amounts of precipitate N in the equivalence and antigen excess zones than when NaCl was added. Furthermore, antigen excess inhibition occurs at much lower antigen concentrations in 9.0 and 0.9% than in 0.09% NaCl. In the 0.00% NaCl series about seven times the antigen N concentration of the equivalence zone is needed for partial inhibition, compared with about twice the equivalence zone antigen N needed for almost complete inhibition with 0.9% NaCl. Some of the possible causes for these differences are discussed. It is suggested and evidence is presented that rabbit pseudoglobulin antibody may contain at least two antibody fractions. One of these precipitates preferentially at the lowest sodium chloride concentration and only to a very small extent in 0.9% or higher salt concentration. For want of further defining criteria this fraction is tentatively called “salt sensitive” antibody. The rest of the pseudoglobulin antibody appears to be much less “salt sensitive.” In the precipitin reaction with euglobulin antibody less nitrogen is precipitated throughout the course of the reaction at the higher salt concentration than at the lower salt concentration. The heterologous reaction between duck ovalbumin and eu- and pseudoglobulin antibody fractions differs somewhat from the homologous reaction. Decreased amounts of precipitation, greater inhibition of the reaction at the higher salt concentrations, and less inhibition in antigen excess were observed.