Buffered solutions, use

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.

Fig. 5.8 Influence of pH, temperature, NaCl concentration, and the concentration of coelenterazine on the light intensity of luminescence reaction catalyzed by the luciferases of Heterocarpus sibogae, Heterocarpus ensifer, Oplophorus gracilirostris, and Ptilosarcus gruneyi. Buffer solutions used 20 mM MOPS, pH 7.0, for Ptilosarcus luciferase and 20 mM Tris-HCl, pH 8.5, for all other luciferases, all with 0.2 M NaCl, 0.05% BSA, and 0.3 p,M coelenterazine, at 23°C, with appropriate modifications in each panel. Various pH values are set by acetate, MES, HEPES, TAPS, CHES, and CAPS buffers.

Fig. 7.4.3 Relationships between the total light emission of polynoidin and the concentrations of the photoprotein (A), H2O2 (B), Fe2+ (C), and EGTA (D). The basic buffer solution used was 50 mM phosphate buffer, pH 6.6, containing 3 mM H2O2, 0.1 mM FeSC>4 and 10 mM EGTA the concentrations of H2O2, FeSC>4 and EGTA were varied in B, C and D, respectively. FeSC>4 was added last to initiate light emission. From Nicolas et al., 1982, with permission from the American Society for Photobiology.

Use the seven-step strategy to calculate the pH of the buffer solution using the buffer equation. Then compare the amount of acid in the solution with the amount of added base. Buffer action is destroyed if the amount of added base is sufficient to react with all the acid.The buffering action of this solution is created by the weak acid H2 PO4 and its conjugate base HP04. The equilibrium constant for this... 

NADH and DCE containing 10 M chloranil, CQ. As supporting electrolytes, 0.5 M 02804 and 0.05 M TPenA+TFPB were added in W and DCE, respectively. The buffer solution used was the same as that in Fig. 5. 

Although the potential to use Caco-2 cells to screen large numbers of formulations under carefully controlled experimental conditions appears attractive, the assumption that this model is suitable to evaluate drug formulations should not be made. In fact, the utility of Caco-2 cells in formulation evaluation is limited because these cells are sensitive to pharmaceutical excipients.112 In addition, the dilution of formulations into the simple buffer solutions used in permeability studies is likely to break the physical integrity of the... 

Valsami-Jones et al. (1998) conducted similar studies with a synthetic, microcrystalline hydroxyapatite in either a Pb or Cd buffered solution. Using AFM, hydroxypyromorphite was observed to grow epitaxially on the hydroxyapatite surface in a clear example of heterogeneous nucleation. Cd removal differed, with the likely formation of a Ca-Cd phosphate solid solution. 

Slope too low Diaphragm contaminated/Clean diaphragm. Adsorption at glass membrane/Service glass membrane. Deswollen glass membrane after measurements in anhydrous solvents/Soak electrode in water between measurements. Old electrode/Regenerate glass membrane. Poor buffer solutions/Use fresh buffer solutions. 

Slope cannot be adjusted Diaphragm blocked/Clean diaphragm. Wrong order of buffer solutions/Use pH 7 buffer as the first buffer. 

Furthermore, in aqueous solutions, the influence of dissolved organic and inorganic species (e.g., buffer solutions used in laboratory experiments, the major ions and dissolved organic matter present in natural waters, trace metals, mineral oxide surfaces) on transformation rates has to be evaluated in each case. As we will see in the following chapters, such species may act as reactants or catalysts, or they may influence the reaction rate indirectly. 

Buffers should have low absorbance and low fluorescence in the regions of excitation and emission. Absorbance will usually be expected to be <0.1 and fluorescence close to zero. This will normally be the case for standard buffers made from analytical-grade reagents or materials of equivalent purity, but they should nevertheless be checked routinely for fluorescence. If a fluorescent component is added to the solution—e.g., as a ligand—it should be checked that the observed fluorescence arises solely from that component. The actual buffer solution used to dissolve or to dialyze the protein should be used for the fluorescence blank. Plastic containers (and stirring bars) may contribute fluorescent agents if these are used, appropriate blanks should be carefully monitored for fluorescence. 

To check this conclusion it was necessary to study the reaction at extremely low oxygen content. At the same time it was desirable that the reaction of oxidation of nitrogen should not change the concentration of oxygen. We adopted a method entirely analogous to that of the buffer solutions used to keep constant the hydrogen ion concentration in solutions. 

The fully oxidized enzyme is inactive the reduced form is the one that reacts with dioxygen. A mixed-valent hydroxylase is also inactive. A bridging exogeneous acetate observed in the oxidized form has its origin in the buffer solution used to crystallize the enzyme. It might be the site at which dioxygen, substrate, or methox-ide product interacts with the core. 

The addition of micelles that migrate counter-current in the capillary can be used for the separation of apolar compounds, particularly when organic solvents such as methanol are added to the buffer solution. Using this method, flavone and flavonol aglycones present in honey were separated, although no specific advantage with HPLC separation using reversed-phase columns was observed. 

Kislalioglu, M. S.. Sethi, R K Malick, A. W., and Behl, C. R. In vitro iontophoretic permeation of a weak base erythromycin from different buffer solutions using hairless mouse skin. Pharm. Pharmacol. Lett. 2 85, 1992. 

The behaviour of arsenic(III) and DMAA on SRA 70 resin as a function of the pH is shown in Figure 28. Neither MMAA nor arsenic(V) was eluted the pH range 4.8-6.4. This is understandable in terms of the dissociation constants of the respective acids and the nature of the buffer solution used for elution. 

Check the background signal for your Tris-HCl buffer solution using large slit-widths and 440 nm excitation. You should observe the Raman scattering, but no other signal. 

The standard buffer solutions used in pH electrode calibration are designed compositionally to have maximal buffer capacities to assure that their advertised pH values are as constant as possible (cf. Bates 1964 Langmuir 1971a). 

For these reasons the calculated salt error is erroneous especially at high ionic strengths, and we must content ourselves with the results of empirical measurements. The agreement between the calculated and experimentally determined values, however, is satisfactory at low ionic strengths. One should always remember that the salt correction depends not only upon the ionic strength but upon the nature of the buffer solution used for comparison as well. Workers in this field should make it a point to mention in their reports the kind and composition of the buffers they employ. 

Effect of Phosphate. The pH 7 buffer solution used to maintain the pH of the Pu(IV) solutions contained KH0PO4. Because phosphate ions are known to complex Pu(IV) (10), a study was conducted to determine if adjustment of the phosphate concentration would alter the nature of the colloidal species and thereby affect the sorption onto silica. 

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