Phosphate concentration, reciprocal

More than 99% of total body calcium is found in bone the remaining less than 1% is in the ECF and ICE Calcium plays a critical role in the transmission of nerve impulses, skeletal muscle contraction, myocardial contractions, maintenance of normal cellular permeability, and the formation of bones and teeth. There is a reciprocal relationship between the serum calcium concentration (normally 8.6 to 10.2 mg/dL [2.15 to 2.55 mmol/L]) and the serum phosphate concentration that is regulated by a complex interaction between parathyroid hormone, vitamin D, and calcitonin. About one-half of the serum calcium is bound to plasma proteins the other half is free ionized calcium. Given that the serum calcium has significant protein binding, the serum calcium concentration must be corrected in patients who have low albumin concentrations (the major serum protein). The most commonly used formula adds 0.8 mg/dL (0.2 mmol/L) of calcium for each gram of albumin deficiency as follows ... 

Fig. 17b, c demonstrate the obtained linear relations between the phosphate concentration and the rate as well as the level of phosphoprotein in double reciprocal plots. 

Figure 7. Langmuir isotherm plot of ko/(T o — k) against the reciprocal of the phosphate concentration, where ko is the calcite growth rate constant in the absence of phosphate and k is the rate constant in the presence of phosphate ( ) ko = 0.824 (n)ko = 1.205 (O)ko = 0.790. Adapted from Ref. 43.

The apparently reciprocal relationship between plasma calcium and phosphate which is seen in clinical practice is largely accounted for by the opposite effects of parathyroid activity upon the calcium and phosphate concentrations. Thus, hyperparathyroidism is associated with high calcium and low phosphate concentrations and hypoparathyroidism with the reverse this is not a biochemical but a physiological reciprocity. A true biochemical or physicochemical reciprocity exists above the solubility product of tricalcium phosphate and presumably explains the irreversible depression of serum calcium by phosphate in renal failure (see Section 4.2). 

Figure 79. Effect of phosphate concentration on hydrolysis rate (reciprocal of the half-life, f50) of chloramphenicol (pH 7.00,97.3°C) (Reproduced from Ref. 14 with permission of the American Pharmaceutical Association.)...

The interpretation of the above data on iodination has been questioned by Buss and Taylor217, and by Grovenstein et a/.218,219. The former workers studied the iodination of 2,4-dichlorophenol at about 25 °C using a stirred flow reactor, the advantages of which are that once a steady state has been reached there is no change in the concentration of the reactive species in the reactor with time and the rate of reaction is simply a product of extent of reaction multiplied by the reciprocal ol the contact time hence it is possible to use unbuffered solutions and low iodide ion concentrations. They found general catalysis by the base component of added phosphate buffers and the observed rate coefficients varied with [H+ ] according to... 

In another report, Michaelis-Menten parameters of ALP have been obtained using a one-shot Lineweaver-Burk (reciprocal) plot. This can be achieved by simultaneously measuring the conversion of 12 independent concentrations of the substrate (4-methylumbelliferyl phosphate) created on-chip. The enzyme was streptavidin-conjugated ALP that was linked to biotinylated phospholipid bilayers coated inside PDMS microchannels. The blue fluorescence of the enzymatic product, 7-hydroxy-4-methyl coumarin, was measured [ 1043]. The surface-bound enzyme was found to have a lower (sixfold) turnover rate than the free enzyme in solutions. After diffusion mixing between two streams (substrate and buffer)... 

The inactivation of bovine Fi -ATPase by FSBA exhibited biphasic kinetics. A double reciprocal plot of the inactivation rate for the fast phase against FSBA concentration gave a curved line, whereas the same type of plot for the slow phase yielded a straight line, giving a Ka value of 0.23 mM. The slow phase was diminished when the enzyme was inactivated in the presence of 0.2 M phosphate. On complete inactivation, about three moles of FSBA bound to one mole of bovine Fi -ATPase. Regardless of the presence of phosphate, His-427 of the (8-subunit was dominantly modified at pH 6, whereas Tyr-368 of the /8-subunit was dominantly modified at pH 8. At pH 7, the two residues were modified in a similar ratio. 

Figure 8.4. Plots of CScat/rp° versus reciprocal reactant concentrations in phosphate transfer reaction (data from Table 8.2). Left plots versus l/Cglucose at different CMg.ATP right plots versus l/CMg ATP at different Ce, ...

Fia. 12. Lineweaver-Burk plot relating the reciprocals of velocity and substrate concentration. For human intestine the substrate was a-naphthyl phosphate, and the L-phenylalanine concentration was 0.005 M. For human placenta the substrate was phenyl phosphate, and the L-phenylalanine concentration was 0.0025 M. 

Fig. 6. Reaction between cytochrome C551 and azurin. Dependence on total azurin concentration of the reciprocal relaxation time for the fast (O) and slow ( ) processes. Condition 0.1 M phosphate buffer pH 7.0 and 25°C (after jump). Solid lines are calculated (see text). The insert shows a temperature-jump relaxation of the reaction between 38 /iM cytochrome C551 and 76 ftM azurin. The monitoring wavelength was 550 nm and (the total absorbance change) = 0.0017. Absorbance scale 1 msec/cm (ascending) and 20 msec/cm (descending).

A linear plot of the reciprocal of the rate versus the reciprocal of the enzyme concentration shows a non-zero intercept. This intercept corresponds to the rate at infinite enzyme (Figure 3) concentration which is equal to the rate of forjpation of the dihydroxyacetone ester (2.4 X 10" s ). A previous study on glucose-e-phosphate dehydrogenase showed that glucose-6-arsenate was formed and the rate constant was 6.3 X 10 ° M s ... 

Figure 4. Reciprocal plots of aldolase activity at different concentrations of 3-deoxy-3-fluorohydroxyacetone-l-phosphate. The reaction was coupled with glycerophosphate dehydrogenase in the presence of NADH to determine the enzyme activity, (see ref. 15). Inserted, slope of the reciprocal plots of aldolase activity vs 3-deoxy-3-fluoro-hydroxyacetone-1-phosphate.

The concentrations of suspended particle matter (SPM) near bottom waters at stations B1 and E3 were 9.6 14.2 and 19.3 24.0 mg/L with averages of 12.2 and 22.2 mg/L, respectively. The reciprocal of the SPM near bottom waters was 0.08 L/g at station B1 and 0.045 L/g at station E3. The annual variation of SPM between the BH98 and BH99 cruises was 25% and 11% at stations B1 and E3, respectively. This implied that the nutrient releases from sediments could be very close to the maximum release. In the experiment, the atom ratios of released nutrients were Si DIN P=40 25 l, which indicated that the phosphorus amount was relatively low compared to the Redfield ratio (Si N P 16 16 l). Fig. 2.45 (Liu et al., 2004) is the plot of time dependent desorption/release of phosphate and silicate from sediments. When surface sediment and seawater were mixed, they were released from sediments (Fig. 

The number of cations in this figure is reduced to the minimum which suffices to bring out the phosphate colloid character of the phosphatides. This figure shows that the higher the reciprocal hexol number (i.e. the closer the phosphatide preparation approximates to pure phosphatide) the lower the reversal of charge concentrations come out (for the rest this displacement does not make its appearance with Na and K) (see further text). 

Fig. 1. Effect of agmatine and NAD on the activity of NAD arginine ADP-ribosyltransferase plotted with NAD as the variable substrate at different fixed concentrations of agmatine. Assays contained 50 mM potassium phosphate (pH 7.0), 1 mg ml ovalbumin, and the following concentrations of agmatine o 0.5 mAf 1 mAf 2 mM O 3 mAf. Reactions were performed at 30 C and initiated with erythrocyte transferase A (9.1 ng/assay). Inset Double reciprocal plot of the activity of transferase A in the absence of acceptor. Solid lines are the theoretical fit of the data to the random rapid equilibrium sequential mechanism described in the text...

FIGURE 11 Reciprocal of response time, l/Tj jr versus buffer concentration for an electrode array coated with an 80 20 HEMArDMA hydrogel and tested in phosphate buffer (1, 5, 10, 25. 50, and 100 mM) and triethanolamine buffer (5, 25, and 50 mM). Symbols represent characteristic response times for (o) a pH increase from 7.2 to 7.4 in phosphate buffer ( ) a pH decrea.se from 7.4 to 7.2 in phosphate ( ) a pH increase from 7.2 to 7.4 in triethanolamine buffer ( ) a pH decrease from 7.4 to 7.2 in triethanolamine buffer. Standard errors are shown. The solid lines represent linear regressions of the data. 

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