Phosphate stability diagram

Fig. 9 A hypothetical More-O Ferrall Jencks diagram for the attack of methoxide on O-aryl phosphate triesters (20) and 5-aryl phosphorothioates (21). Note that the diagram for attack of a metal-coordinated methoxide would be similar, but Mx +-coordination would push the TS toward the S-corner, possibly stabilizing the pentacoordinated intermediate to the point that the reaction occurs stepwise with the likely rate-limiting step being breakdown.

STABCAL was also used to construct pE-pH stability fields for chloropyromorphite, hinsdalite, plumbogummite, tricadmium diphosphate, tricopper diphosphate, and hopeite (Fig. 7). These diagrams allow for estimation of stability with respect to pH and to the presence of insoluble sulphides. The NBS thermodynamic database (Wagman et al. 1982) was used as a source of thermodynamic data. The total concentrations chosen for each metal were selected to produce a stability region for the metal phosphate solid. In some cases, this was a very low total concentration (e.g., CTPb =1 x 10 10 M for Pb). In other cases, the total metals concentration was high (e.g., C r.cd— 1 x 10 3 M for Cd). The modelling exercise used typical equilibrium concentrations for MSW bottom ash leachates as shown in Table 2. 

Fig. 12. Diagram of elution pattern of red cell acid phosphatase and various markers on Biogel P 60. The position of the various protein markers was determined both by optical density determination and by starch gel electrophoresis of the individual fractions (83). The experiment was carried out using a polyacrylamide gel (Biogel P 60, 50-150 mesh exclusion limit >60,000 Bio-Rad Laboratories, California) in 0.05 M tris buffer, pH 8.0, containing 0.08% (v/v) Tween 80 and 0.1% (v/v) 2-mercaptoethanol to stabilize the enzyme. Column 60 X 4 cm. Flow rate 20 ml/hr, 4 ml fractions. (A) OD at 280 nm, ( ) OD at 540 nm, ( ) LDH assay with p-nitrophenyl phosphate for AcP. From Hopkinson and Harris (85).

Fig. 20. The diagram at the top is a schematic view of the active center as deduced from the X-ray data from the protein and several substrate related complexes. Bi, Ri, pi, R2, and B2 indicate the relative positions of the bases, riboses and phosphate of the dinucleotide analog UpcA. Position pi is occupied by S(V in the protein crystal. CMP, UMP, and analogs of these occupy Bi, Ri, and pi predominantly. 5 -AMP occupy Bj, Ra, and pi while 3 -AMP and 3 5 -A > p occupy Ba and R2 predominantly, and possibly to a lesser extent, Bi and Ri. B2 is the probable position of the second pyrimidine in dinucleotides such as CpU. The phosphate position in C > p cannot be observed owing to digestion but would be at pi if the base occupies the same position as in CMP. Four His 119 positions are indicated. I coincided with Pi but is a possible position in the absence of S(V or nucleotides. II is behind III and may be occupied by solvent. Ill is slightly stabilized by 3 -CMP. IV is the position occupied when B2 and It2 are occupied by adenosine phosphates. His 12 is behind pi and Ri. There is a solvent molecule, presumably water, behind p, as indicated by H20. Lys 41 enters from the upper right and is not in contact with pi but might contact pi. Asp 121 enters from...

As evident from the binary CaO-P2Os phase diagram, several calcium phosphate phases with different thermal stabilities exist. Figure 6.4 shows the binary... 

Figure 9.6 illustrates the relative stabilities of several phosphate compounds in soils of various pH values. Soil solution compositions can be plotted on the diagram by measuring soil pH and soluble phosphate concentrations. Data above a compound s isotherm represent supersaturation with respect to the solid, indicating that the compound will precipitate. Data below the isotherm indicate undersaturation of phosphate in the soil solution with respect to that compound, so that the solid, if... 

Figure 7.3. (a) X-ray crystal structures of adenylate kinase (ADK) showing the open (denoted by O ) and closed (denoted by C ) states of the enzyme. See plate section for color version, (b) Schematic free-energy contour diagram presented for the different conformational states of ADK. The reaction takes place in the state where both the LID and the NMP domains are closed, with the two substrates (ATP and AMP) inside. After the phosphate transfer, the product molecules (two ADP) get released by opening of ftie domains. The proposed catalytic cycle involves closed (C) and half-open-half-closed (HOHC) states, and not the full open state. The HOHC state is stabilized by water. The millisecond conformational fluctuation observed in the experiment may involve fluctuation between HOHC and the fully open state. Adapted with permission fiomJ P s. Chem. A, 115 (2011), 3691-3697. Copyright (2011) American Chemical Society. 

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