Sodium phosphates, structure

Figure 10.1 Types of phosphate structures, (a) Where x = 12 to 14, the structure represents sodium polyphosphate, a phosphate typically used in HW heating and industrial steam boiler formulations. The structure is ill defined and described as glassy rather than crystalline. Where x = 2, it represents sodium tripolyphosphate, (b) This is the structure where effectively, x = 0, and represents trisodium phosphate (sodium orthophosphate), which is commonly supplied in either crystalline or anhydrous powder form and used as an alkalinity booster, boiler boil-out cleaner, and metal surfaces passivator.

Dissolve the protein to be reduced at a concentration of l-10mg/ml in 20mM sodium phosphate, 0.15M NaCl, pH 7.4. Other buffers and pH values also may be used. Do not add a denaturant to unfold protein structure. 

Draw the Lewis structure of sodium phosphate, Na3P04. (Be Careful - this is tricky.)... 

Prabakar, S., Wenslow, R.M., and Mueller, K.T. (2000) Structural properties of sodium phosphate glasses from Na -> cross-polarization NMR./. Non-Cryst. Solids, 263, 82-93. 

Pig. 4. CD spectra in the near and far UV of apo- and heme-hemopexin. The CD spectra of rabbit apo- and heme-hemopexin (solid line and dashed line, respectively) at pH 7.4 in 0.05 M sodium phosphate buffer are shown. The increases in ellipticity in the near UV are attributable to changes in tertiary conformation leading to altered environments of aromatic residues, particularly tryptophan. The unusual positive ellipticity in the far UV is attributable to tryptophan-tryptophan interactions that are perturbed by heme binding 124, 130). This positive signal precludes analysis of the secondary structure of hemopexin using current CD-based algorithms. 

Fig. 14.3. Secondary structural changes of prion protein, (32-microglobulin and a-synuclein upon UV exposure under their respective amyloid-forming conditions. Far UV CD spectra of (a) prion protein in 20 mM sodium phosphate buffer (pH 6.8) containing 100 mM NaCl, 3M urea and 1M GdmCl. Inset shows the Far UV CD spectrum of native prion protein (b) (32-microglobuhn in 50 mM citrate buffer (pH 2.5) containing 100mM KC1 and (c) a-synuclein in 20 mM 11EPES- NaOl I buffer (pH 7.0) containing 100 mM NaCl and 0.5 mM SDS. In each panel, curves 1 and 2 show the far UV CD spectra of the protein before and after exposure to UV light, respectively. Panel 3a reproduced from [3]...

As an illustration of HIC technique, the recombinant human growth hormone (hGH) and methionyl hGH (met-hGH) were well-separated by the HIC technique [14]. The optimized conditions were found to be IM ammonium phosphate dibasic, pH 8.0/propanol (99.5 0.5) and 0.1 M sodium phosphate dibasic, pH 8.0/propanol (97.5 2.5) for mobile phase A and B, respectively, with a descending gradient from 100% A to 100% B in 30 minutes at a column (TSK-phenyl 5PW, 75 x 7.5 mm) temperature of 30°C. Note that the addition of a small amount of propanol as organic modifiers significantly decreases elution time while maintaining resolution and efficiency. This HIC method allowed separation of several hGH variants from the main hGH peak while retaining their native structures. 

Thereafter, crystals were brought back to the aerobic 25% MPD solution, buffered with 50 mAf sodium phosphate, pH 5.5. This procedure is based on Avigliano et al. s (157) method of preparing T2D ascorbate oxidase in solution and was modified by Merli et al. (159) for use with ascorbate oxidase crystals. The 2.5-A-resolution X-ray structure analysis by difference-Fourier techniques and crystallographic refinement shows that about 1.3 copper ions per ascorbate oxidase monomer are removed. The copper is lost from all three copper sites of the trinuclear copper species, whereby the EPR-active type-2 copper is the most depleted (see Fig. 10). Type-1 copper is not affected. The EPR spectra from polycrystalline samples of the respective native and T2D ascorbate oxidase were recorded. The native spectrum exhibits the type-1 and type-2 EPR signals in a ratio of about 1 1, as expected from the crystal structure. The T2D spectrum reveals the characteristic resonances of the type-1 copper center, also observed for T2D ascorbate oxidase in frozen solution, and the complete disappearance of the spectroscopic type-2 copper. This observation indicates preferential formation of a Cu-depleted form with the holes equally distributed over all three copper sites. Each of these Cu-depleted species may represent an anti-ferromagnetically coupled copper pair that is EPR-silent and that could explain the disappearance of the type-2 EPR signal. 

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