Activity of NaCl

The chloride concentration thus corresponds to the sulphite concentration in the test solution. The chloride ISE can be used for various thermodynamic measurements, such as determination of the activity of NaCl [361], also in the pressure range 0.1-60MPa and temperature of 0-25 [217]. This ISE is also... 

In this equation, fi a is the chemical potential of dissolved KCl in the standard state. The activities of the two electrolytes in solution (NaCl, KCl) change as K exchanges Na, and the activity of NaCl increases while that of KCl decreases in solution. The overall free energy change in solution per mole of K" adsorption is... 

The expressions for the activities of NaCl, CaCl 2 and LaCl3 in terms of their molalities and mean ionic activity coefficients ... 

The polyelectrolyte also affects the distribution of coions (small ions having a charge of the same sign). This is known as the Donnan effect, which may be illustrated by envisaging a system with two compartments that are separated by a semipermeable membrane. This membrane does not allow passage of polymers but is permeable for small ions. Assume that one compartment initially contains the polyelectrolyte (PEZ ) and sufficient counterions (Na+) to neutralize the charge, while the other compartment initially contains NaCl. At equilibrium, the activity of NaCl (which means the free ion activity a+) must be equal in both compartments. This implies that CD will diffuse towards the other compartment, and the condition of... 

The activity of a salt can then be divided between cation and anion. By measuring the activities of NaCl, NaBr, NaNOj, and NaC104, for example, the contribution of Na+ to the total activity can be soiled out. This process is very laborious calculating the ion activity directly would be much quicker. 

According to Wellman (1969), the fugacity of NaCl in equilibrium with nepheline (NaAlSi04) and sodalite (3NaAlSi04 - NaCl)at 600°C, 1 bar, is 10 bars, and the fugacity of pure halite at the same T,P is 20- 5.780 Thus the activity of NaCl at nepheline-sodalite equilibrium at these conditions is lO " bars, using a pure halite at T,P stan-... 

For the remainder of this analysis we shall understand the concentrations to be the osmotic activity of NaCl in the respective solutions. For the epitheUal models under consideration we shall suppose that the volume flow from mucosa to serosa is positive when the baths are identical and that this flow declines with increases in mucosal bath salt concentration. Denote by C that increase in mucosal bath... 

Because A/r, is the difference of two constant standard state chemical potentials, it must be a constant. The ratio of activities of NaCl or HO Ac is fixed provided that the temperature and pressure are held constant. 

In the following example, data from Archer (1992) on the stoichiometric mean ionic activity of NaCl at 25 are fitted to Equation (15.28), with a and B as unknowns. 

Consider, for example, the measurement of a sample that contains equal 1.0-mM activities of NaCl, KCl, and CaC. According to Eq. (13), a sodium-selective electrode must show the following selectivity coefficients to reliably quantitate sodium in this sample 0-010. 

The equilibrium conditions of equal activities of NaCl and MgCl2 are... 

Note that the activity of NaCl in liquid water is not appro tching the NaCl concentration for high dilution but its square (/[Pg.99]

The Debye-Htickel limiting law predicts a square-root dependence on the ionic strength/= MTLcz of the logarithm of the mean activity coefficient (log y ), tire heat of dilution (E /VI) and the excess volume it is considered to be an exact expression for the behaviour of an electrolyte at infinite dilution. Some experimental results for the activity coefficients and heats of dilution are shown in figure A2.3.11 for aqueous solutions of NaCl and ZnSO at 25°C the results are typical of the observations for 1-1 (e.g.NaCl) and 2-2 (e.g. ZnSO ) aqueous electrolyte solutions at this temperature. 

NaCl, interact with the sulphur and vanadium oxides emitted from the combustion of technical grade hydrocarbons and die salt spray to form Na2S04 and NaV03- These conosive agents function in two modes, either the acidic mode in which for example, the sulphate has a high SO3 thermodynamic activity, of in the basic mode when the SO3 partial pressure is low in the combustion products. The mechanism of coiTosion is similar to the hot coiTosion of materials by gases widr the added effects due to the penetration of tire oxide coating by tire molten salt. 

Urokinase (from human urine) [9039-53-6] Mr 53,000, [EC 3.4.21.31]. Crystn of this enzyme is induced at pH 5.0 to 5.3 (4") by careful addition of NaCl with gentle stirring until the soln becomes turbid (silky sheen). The NaCl concentration is increased gradually (over several days) until 98% of saturation is achieved whereby the urokinase crystallises as colourless thin brittle plates. It can be similarly recrystd to maximum specific activity [104K CTA units/mg of protein (Sherry et al. J Lab Clin Med 64 145 1964)]. [Lesuk et al. Science 147 880 1965 NMR Bogusky et al. Biochemistry 28 6728 1989.] It is a plasminogen activator [Gold et al. Biochem J 262 1989 ]. 

It is not appropriate here to consider the kinetics of the various electrode reactions, which in the case of the oxygenated NaCl solution will depend upon the potentials of the electrodes, the pH of the solution, activity of chloride ions, etc. The significant points to note are that (a) an anode or cathode can support more than one electrode process and b) the sum of the rates of the partial cathodic reactions must equal the sum of the rates of the partial anodic reactions. Since there are four exchange processes (equations 1.39-1.42) there will be eight partial reactions, but if the reverse reactions are regarded as occurring at an insignificant rate then... 

Finally, as an example of a highly soluble salt, we may take sodium chloride at 25° the concentration of the saturated solution is 6.16 molal. The activity coefficient of NaCl, like that of NaBr plotted in Fig. 72, passes through a minimum at a concentration between 1.0 and 1.5 molal and it has been estimated2 that in the saturated solution the activity coefficient has risen to a value very near unity. Writing y = 1.0, we find that the work required to take a pair of ions from the surface of NaCl into pure water at 25° has the rather small value... 

Although the viscosity B-coefficients for the fluorides are not known, we see. that the value for the ionic entropy of F" listed in Table 45 is — 2.3 + 2, very different from the value +13.5 for Cl". The value for F- is, in fact, very near the value —2.49 for (OH)-. We have then the very interesting question, whether the activities of the fluorides will fall in line with the other halides. In structure the ion F" certainly resembles Cl" and the other halide ions but according to the tentative scheme proposed above, we should perhaps focus attention on the solvent in the co-sphere of each ion. In this case we should expect to obtain for the fluorides a family of curves similar to that of the hydroxides, in contrast to that of the chlorides. The activities are known as a function of concentration for NaF and KF only. It is found that the curve for NaF lies below that of KF—that is to say, the order is the same as that of NaOH and KOII, in contrast to that of NaCl and KC1. 

Fig. 3.1.5 Effects of salt concentration on the activity of Cypridina luciferase (solid lines) and quantum yield (dotted lines). In the activity measurement, Cypridina luciferin (1 pg/ml) was luminesced with a trace amount of luciferase in 2.5 mM HEPES buffer, pH 7.5, containing a salt to be tested, at 20°C. In the measurement of quantum yield, luciferin (1 pg/ml) was luminesced with luciferase (20 pg/ml) in 20 mM sodium phosphate buffer (for the NaCl data) or MES buffer (for the CaCl2 data), pH 6.7.

Fig. 3.1.7 Effects of temperature on the activity of Cypridina luciferase (solid line) and the quantum yield of Cypridina luciferin (dashed line). Luciferin (1 pg/ml) was luminesced in the presence of luciferase (a trace amount for the activity measurement 20 pg/ml for the quantum yield) in 50 mM sodium phosphate buffer, pH 6.8, containing 0.1 M NaCl.

Dried shrimp was ground, defatted with benzene, and then extracted with cold water. The luciferase extracted was purified first by a batch adsorption onto DEAE cellulose (elution with 0.4 M NaCl), followed by gel filtration on a column of Sephadex G-150, anion-exchange chromatography on a column of DEAE-cellulose (gradient elution 0.05-0.5 M NaCl), and gel filtration on a column of Ultrogel AcA 34. The specific activity of the purified luciferase was 1.7 x 1015 photons s 1 mg-1, and the yield in terms of luciferase activity was about 28%. 

The bioluminescence reaction of Oplophorus is a typical luciferin-luciferase reaction that requires only three components luciferin (coelenterazine), luciferase and molecular oxygen. The luminescence spectrum shows a peak at about 454nm (Fig. 3.3.1). The luminescence is significantly affected by pH, salt concentration, and temperature. A certain level of ionic strength (salt) is necessary for the activity of the luciferase. In the case of NaCl, at least 0.05-0.1 M of the salt is needed for a moderate rate of light emission, and about 0.5 M for the maximum light intensity. 

Fig. 3.3.2 Influence of pH on the activity of luciferase ( ) and the quantum yield of coelenterazine (o) in the bioluminescence of Oplophorus. The measurements were made with coelenterazine (4.5 pg) and luciferase (0.02 pg) for the former, and coelenterazine (0.1 pg) and luciferase (100 pg) for the latter, in 5 ml of 10 mM buffer solutions at 24° C. The buffer solutions used sodium acetate (pH 5.0), sodium phosphate (pH 6.0-7.5), Tris-HCl (pH 7.5-9.1), and sodium carbonate (pH 9.5-10.5), all containing 50 mM NaCl. Replotted from Shimomura et al., 1978, with permission from the American Chemical Society.

Quantum yield and luciferase activity The quantum yield of coelenterazine in the luminescence reaction catalyzed by Oplophorus luciferase was 0.34 when measured in 15 mM Tris-HCl buffer, pH 8.3, containing 0.05 M NaCl at 22°C (Shimomura et al., 1978). The specific activity of pure luciferase in the presence of a large excess of coelenterazine (0.9pg/ml) in the same buffer at 23°C was 1.75 x 1015 photons s 1 mg-1 (Shimomura et al., 1978). Based on these data and the molecular weight of luciferase (106,000), the turnover number of luciferase is calculated at 55/min. 

Fig. 4.1.11 Influence of the concentration of apoaequorin on the yield of regenerated aequorin after 12 h at 4°C (solid line), and on the initial light intensity of the apoaequorin-catalyzed luminescence of coelenterazine (dashed line). The regenerated aequorin was measured with a 10 pi portion of a reaction mixture (0.5 ml) made with 10 mM Tris-HCl, pH 7.5, containing 1 mM EDTA, 5 mM 2-mercaptoethanol, 10 pi of methanolic 0.6 mM coelenterazine, and various amounts of apoaequorin. The luminescence activity of apoaequorin was measured in 2 ml of 10 mM Tris-HCl, pH 7.5, containing 0.5 M NaCl, 2 mM CaCb, 2 mM 2-mercaptoethanol, 10 pi of methanolic 0.2 mM coelenterazine, and various amounts of apoaequorin. Reproduced with permission, from Shimomura and Shimomura, 1981. the Biochemical Society.

Properties of the luciferases. According to Shimomura and Flood (1998) and Shimomura et al. (2001), all Periphylla luciferases L, A, B and C catalyze the oxidation of coelenterazine, resulting in the emission of blue light (Amax 465 nm). Luciferases B (40 kDa) and C (80 kDa) are apparently the dimer and tetramer, respectively, of luciferase A (20 kDa). The presence of a salt is essential for the activity of luciferase, and the optimum salt concentration is about 1M in the case of NaCl for all forms of luciferases. The luminescence intensity of luciferase L is maximum near 0°C, and decreases almost linearly with rising temperature, falling to zero intensity at 60°C the luminescence intensity profiles of luciferases A, B and C show their peaks at about 30°C (Fig. 4.5.3). The Michaelis constants estimated for luciferases A, B and C with coelenterazine are all about 0.2 xM, and that for luciferase L is 1.2 jiM. 

Luminescence activity. The specific luminescence activities (quanta/s emitted from 1ml of a solution of A280nm,icm 1.0) of luciferases A, B and C are in a range of 1.2 4.1 x 1016 photons/s when measured with the standard assay buffer (20 mM Tris-HCl, pFl 7.8, containing 1M NaCl, 0.05% BSA, and 0.14 xg/ml of coelenterazine, at 24°C). These are the highest specific activities of coelenterazine luciferases. 

Renilla luciferase. The luciferase of Renilla reniformis has been purified and characterized by Karkhanis and Cormier (1971) and Matthews et al. (1977a). The purified luciferase has a molecular weight of 35,000, and catalyzes the luminescence reaction of coelenterazine. The luciferase-catalyzed luminescence is optimum at pH 7.4, at a temperature of 32°C, and in the presence of 0.5 M salt (such as NaCl or KC1). The luciferase has a specific activity of 1.8 x 1015 photons s"1mg"1, and a turnover number of 111/min. The luminescence spectrum shows a maximum at 480 nm. The absorbance A28O of a 0.1% luciferase solution is 2.1. The luciferase has a tendency to self-aggregate, forming higher molecular weight species of lower luminescence activities. 

Assay of photoprotein. The activity of the photoprotein was measured in 1ml of 20 mM Tris-HCl buffer, pH 8.0, containing 0.6 M NaCl at room temperature. The intensity and total amount of light emitted were recorded. The luminescence intensity is markedly intensified by adding 5 il of catalase solution (crystalline bovine liver catalase 1.5 mg/ml) and 10 pi of 3% H2O2. 

The concentrated luciferase solution is dialyzed overnight against 4 liters of 1 mM Tris-HCl buffer, pH 8.5, containing, 0.1 mM EDTA and 3 mM DTT. Then luciferase is further purified on a column of DEAE-BioGel A (1 x 25 cm, Bio-Rad) by elution with a linear increase of NaCl from 0 to 100 mM in the same buffer as that used in dialysis. The purified luciferase had a specific activity (based on initial maximum intensity) of approximately 8.5 x 1014 quanta sec 1mD1Aj810. 

Step 3. The photoprotein fractions are combined and the NaCl concentration of the solution is reduced to 50 mM by gel filtration through a column of Sephadex G-25. Then, the solution is poured onto a column of DEAE cellulose. The photoprotein adsorbed on the column is eluted by a linear increase of NaCl concentration from 50 mM to 0.4 M in the same pH 6.7 buffer. Active fractions are combined and concentrated by ammonium sulfate precipitation. 

In order to solubilize the bound luciferase, the pellet is homogenized with 20-30 volumes of cold 10 mM Tris-HCl buffer, pH 7.5, containing 1M NaCl, and the activity of the homogenate is measured. The homogenate is centrifuged and the activity of supernatant is also measured. A close agreement between the two measurements indicates that 1 M NaCl has solubilized the bound luciferase. If the two values differ significantly, a further effort of solubilization is needed (see Section C1.3). 

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