Intrinsic equilibrium dissociation constant

The equilibrium dissociation constants, both macroscopic or global Kn) and microscopic or intrinsic (kn), for the various ES complexes are... 

The overall dissociation constant obtained comprises the intrinsic dissociation constants for the ligands and the equilibrium constant for the conformational transition [68],... 

Typical values of pK[nt and pfor a humic acid are 2.67 and 4.46. The introduction of the electrostatic factor into the equilibrium constant is analogous to the coulombic term used in the definition of the intrinsic surface complexation constants. In addition another binding site (WAH) is recognised which is thought to behave as a weak acidic phenolic functional group. Although this site does not contribute to the titratable acidity and, therefore, no pK is needed for proton dissociation, it is involved in metal complexation reactions. The total number of the three monoprotic sites is estimated from titratable acidity and then paired to represent the humic substance as a discrete non-interacting mixture of three dipro-tic acids, which act as the metal complexation sites. The three sites are... 

It had been previously shown by Rapoport et al. (8) that native PPase binds two divalent metal ions (Mg2+, Co +, Mn +) per subunit. We have now used equilibrium dialysis to extend these studies, by measuring the effect of added Pi on Mn2+ and Co + binding (9). The results (Figure 1) demonstrate that in the presence of Pi a third divalent metal ion is bound per subunit. For Mn2+, one intrinsic dissociation constant characterizes the bind-... 

Figure 3.12. The allosteric model of receptor activation, inhibition and partial agonism. The receptor itself is characterized by an intrinsic conformational equilibrium that favours the inactive state. Agonists bind exclusively to the active state, with a characteristic dissociation constant and thus increase the over-...

Fig. 4A presents a Scatchard plot of results obtained by flowing a range of sIL-6R concentrations across the sensor chip and measuring the equilibrium binding response Rp. The slope signifies a intrinsic association equilibrium constant (K x) 2.4x10 (a dissociation constant of 42 nM) which... 

The intrinsic equilibrium constants for the diffuse layer model are similar to those for the constant capacitance model where P is replaced by Equations (6.10) and (6.11) describe surface protonation and dissociation, respectively. Metal surface complexation is described by two constants similar to tliat defined in Eq. (6.12) for strong and weak sites ... 

Kinetic performances of Rh/AljOj and Pt/AljO, catalysts have been examined using the competitive adsorption model. The intrinsic rate constant of NO dissociation k, and the equilibrium adsorption constant of NO X-nq, are considerably higher on RI1/AI2O3 than on Pt/Al203. This result corroborates earlier observations on the adsorption of NO on Rh (111) and Pt (111) surfaces showing that NO dissociates easier on Rh than on Pt [3-5]. 

It is generally difficult to determine the ion activity coefficients, and one commonly makes shift with values calculated with semiempirical equations see Section 2.3.2. Anyway, y decreases with an increase in total ionic strength. This means that adding any other electrolyte will decrease the activity coefficients, causing the solubility and the dissociation to increase. For instance, if KNO3 is added to a solution of CaCl2, this affects the latter s dissociation equilibrium. y+ and y decrease and y0 remains at 1, and—since the intrinsic dissociation constant remains unaltered—it thus follows from (2.25) that the concentrations of Ca2+ and CP increase and that of the undissociated salt decreases. 

Dissociation constants and corresponding pK values of the drugs were obtained from measured free-base solubilities (determined at high pH s) and the concentrations of saturated solutions at intermediate pH s. Morphine, fentanyl, and sufentanil exhibited pJCa values of 8.08,8.99, and 8.51, respectively. Over the pH range of 5 to 12.5 the apparent solubilities are determined by the intrinsic solubility of the free base plus the concentration of ionized drug necessary to satisfy the dissociation equilibrium at a given pH."... 

In Eqn, 39 we have had to introduce new symbols over those in Eqn, 30 to account for the presence of two substrates S and P. There is now an intrinsic dissociation constant R for each substrate. Resistances terms R,2 and Rji, describing the zero trans situation, are defined for each substrate and also for the equilibrium exchange experiment R involving just a single substrate S or P. There are also defined cross-resistances R and for the situation where S is present only at one side of the membrane and P only at the other. These cross-resistances can be derived from the resistances obtainable by single substrate experiments (see Table 6 where these... 

As the pre-equilibria in Schemes 5-10 and 5-11 are not identical and their equilibrium constants are therefore likely to be different from one another, the rate constants k - and are not intrinsic rate constants of the corresponding slow dissociation steps, but are dependent in addition on the constants of these pre-equilibria. 

Note that when the concentration of added salt is very low, Debye length needs to be modified by including the charge contribution of the dissociating counterions from the polyelectrolytes. Because the equilibrium interaction is used, their theory predicts that the intrinsic viscosity is independent of ion species at constant ionic strength. At very high ionic strength, the intrachain electrostatic interaction is nearly screened out, and the chains behave as neutral polymers. Aside from the tertiary effect, the intrinsic viscosity will indeed be affected by the ionic cloud distortion and thus cannot be accurately predicted by their theory. 

One can measure the concentration of the intrinsic lattice defects by measuring the ratio of the paired and dissociated pairs and having a previous value for the equilibrium constant. 

There are four sites available for binding 02, but only one from which bound 02 can dissociate. Thus, from the law of mass action, the (overall) extrinsic equilibrium constant is equal to 4k /k- = 4X. Similarly, the extrinsic constant denoted by X2 is given by 1K2, where K2 is the intrinsic constant, and by the same reasoning K% = and Ke4 = JK4. 

This equation is essentially an equilibrium constant relationship between the electron and hole concentrations in the semiconductor. It is much like the ionization constant expression for the dissociation of water, which can be related to the concentrations of H+(aq) and OH (aq) through the relationship [H+][OH ] = /fw = 1 x 10 " M. The only difference between these two expressions is that the temperature dependence of the water dissociation equilibrium constant is contained implicitly in the value of K, but is explicit in the relationship expressed by equations (5) and (6). The most important point to remember is that increases in the sample temperature will produce exponential increases in the electron and hole concentrations for an intrinsic semiconductor. Thus, the conductivity of intrinsic semiconductors increases exponentially with temperature. In contrast, the conductivity of metals decreases with increasing temperature. ... 

For the precise examination of the complexation equilibria in linear carboxylate polyion systems, the Kj values of the Ag -CmDx and the Ca -CmDx binding equilibria have been examined at various a values [42,43]. In this case, the Kj, values resolved in the presence of trace-level concentrations of metal ion have been substituted for the intrinsic constant, Km values. Concurrent measurements of p[H] and p[M], at equilibrium, of the M /(Na, H )CmDx/Na (excess) system enabled the simultaneous analyses of the acid-dissociation and the metal complexation equilibria. The log K(P, and the log K g values determined on the metal association studies are plotted versus a in Fig. 29. The increase in the log KjS value with a is more pronounced with the higher valent metal ion. It should be pointed out as well that log K, , is greatly influenced by the added salt concentration in the Ca ion-binding system. 

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