Equilibrium pairing constants

Cheng-Prusoff correction, published by Cheng and Prusoff (Biochem. Pharmacol. 22, 3099-3108, 1973), this method is used to derive the equilibrium dissociation constant of a ligand-receptor (or enzyme) pair from the experimentally observed ICso (concentration that produces 50% reduction in effect) for that molecule see Eqn 4.11. 

Consider a system in which the membrane ions form stable ion-pairs with both ions, whose equilibrium formation constants are Kj indKy. Then, according to (3.2.10), (3.2.14) converts to... 

Fig. 11. Plot of initial cation transport rates for various carrier/alkali picrate pairs versus equilibrium extraction constants log Ke the points are experimental data, the curve is calculated [6.1, 6.4,6.17]. For analytical reasons the Ke values were determined in conditions different from those of the transport experiments the carriers are cryptands (for [2.2.C5] and [2.1.C5] see structures in [6.1]) dibenzo-18-crown-6, DB18-6 and valinomycin, VAL picrate, P.

Table 12.1 lists elements in seawater that have concentrations greater than 0.1/tmol kg-1. The first seven elements in Table 12.1 (Cl, Na, Mg, S, Ca, K and C) have concentrations greater than or equal to 0.002 mol kg 1 and are generally treated as the major ionic constituents of seawater. The ion pairing constants of these relatively weakly interacting elements have been studied as a function of temperature, pressure and ionic strength. An equilibrium speciation...

Try-70 is conserved in all transaminases1 3 these transaminases utilize Glu a-KG pair as substrates. X-ray studies have shown that Tyr-70 interacts with the phosphate part of the coenzyme. Y70 F mutant was prepared to examine whether or not Tyr-70 could be a catalytic base. The Y70F mutant showed 15% of the activity of the wild-type enzyme thus, it was quite unlikely that Tyr-70 was the catalytic base. However, Tyr-70 was involved in the interaction with the coenzyme, since the affinity towards the coenzyme was significantly reduced in Y70 F mutant.49-513 The equilibrium dissociation constants for the PMP holoenzyme complex were 1.3 nM and 30 nM for the wild-type and mutant... 

Solution. Experimental phase equilibrium data for the quaternary system were fitted to the NRTL equation by Cohen and Renon. The resulting binary pair constants in (5-68) and (5-69) are... 

TABLE 7.1 Equilibrium Dissociation Constants of Organoalkali Metal Salts of Polystyryl Carbanions and the Propagation Rate Constants for the Corresponding Ion Pairs and Eree Ions in THE at 25 °C [48, 97-99]... 

The dimerization has a second-order rate constant of 200 50 M s at 25 C, which is lowered by a factor of 2 X 10 in the presence of DNA [21]. An apparent equilibrium binding constant of 8.4 X 10 was found for the Co(III)—O2—Co(III)/DNA adduct, with binding of one //-peroxo complex approximately every three base pairs [21]. Of interest is the fact that the variously colored Co complexes have the ability to nick DNA in the presence of light [42, 43], reminiscent of the reaction of simple Co(III) complexes (Section 1.3.1). As the Co-substituted bleomycin has been extensively investigated for tumour imaging and found to accumulate selectively in certain cancer cells, the possibility of selective attack by a later light-induced reaction is attractive. 

Table 2 Equilibrium dissociation constants of organoalkali metal salts of polystyryl carbanions and the propagation rate constants for the corresponding ion pairs and free ions in THE at 25 O "...

The specificity of a bimolecular act in liquid, as already mentioned, is that particle-reactants at first meet in the same cage and then, at a sufficient activation, react in the environment of solvent molecules. The formation of the A.B pair is accompanied, in the general case, by a change in entropy ASab and enthalpy A/ ab of the system equilibrium rate constant ATab is related to them by the known correlation... 

The energy AG i can reach a value of -20 kJ/mol. The experimentally observed rate constant is iexp = ab o where k is the rate constant of transformation of the pair A.B into the reaction products. During transformation the pair A.B with Pab is transited to the transition state (A.B) with p. In the general case, the transition state has the different configuration than the equilibrium pair A.B, and Pab I ab -The contribution of electrostatic repulsions to the formation of the transition state... 

Table 1.13.1 contains values of equilibrium ion pair constants of some positively charged cobalt(III) complex cations and univalent anions, including also the divalent 804 " anion, for comparison. 

Table 1.13.1. Equilibrium ion pair constants (A jp) for some cobalt(III) complex...

One can write acid-base equilibrium constants for the species in the inner compact layer and ion pair association constants for the outer compact layer. In these constants, the concentration or activity of an ion is related to that in the bulk by a term e p(-erp/kT), where yp is the potential appropriate to the layer [25]. The charge density in both layers is given by the algebraic sum of the ions present per unit area, which is related to the number of ions removed from solution by, for example, a pH titration. If the capacity of the layers can be estimated, one has a relationship between the charge density and potential and thence to the experimentally measurable zeta potential [26]. 

The general formula for the initiator species can be written H B, where the degree of separation or ion pairing depends on the polarity of the medium and the possibility of specific solvation interactions. If we represent the equilibrium constant for the reactions in (6.DD) and (6.EE) by K, the initiator concentration can be written as... 

Ionic polymers may exist as undissociated, unsolvated ion pairs undissociated ion pairs solvated to some extent solvated ions dissociated to some extent or some combination of these. The propagation rate constant kp and the dissociation equilibrium constant K of the lithium salt of anionic... 

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