Association constant, inverse

Optical activity in metal complexes may also arise either if one of the ligands bound to the metal in the first co-ordination sphere is itself optically active or if the complex as a whole lacks a centre of inversion and a plane of symmetry. Thus all octahedral cts-complexes of the tris-or bis-chelate type have two isomeric forms related by a mirror plane, the d- and /-forms. These species have circular dichroism spectra of identical intensities but opposite in sign. The bands in the circular dichroism spectrum are, of course, modified if ligand exchange occurs but they are also exceedingly sensitive to the environment beyond the first co-ordination sphere. This effect has been used to obtain association constants for ion-pair formation. There also exists the possibility that, if such compounds display anti-tumour activity, only one of the mirror isomers will be effective. 

A further problem is that ion association, that is, the tendency of oppositely charged ions to form pairs or larger aggregates in solution, becomes increasingly important as the temperature rises unless the density is kept constant this is because ion association is inversely related to the dielectric constant (relative permittivity) of the medium, which is correlated with density for a given solvent. Helgeson and co-workers have attacked these problems theoretically for aqueous solutions up to 1000 °C.28 For our purposes, it is enough to note that quantitative treatment of ionic reactions in sub- and supercritical aqueous solutions is extremely difficult at present, and likely to remain so for some time. 

It is clear from Eqs. (3) and (4) that Kj and inact are complex functions of several microrate constants. It is important to note that only under restrictive conditions can inact be equated with k2, e.g., when 4 is much greater than k2 plus k3. Similarly, K cannot simply be equated with the inverse of the equilibrium association constant for inhibitor and free enzyme. 

Plot the ratio I0/I vs. [TNS] for each pH and calculate the apparent value of the association constant Ka of TNS-BSA complex. Are the association constants calculated identical to those obtained by plotting the inverse equation 1/AI vs. 1/[TNS] ... 

The equilibrium association constant for this reaction is defined as ki/kj and provides an index of the affinity between the binding sites and the ligand. The inverse of the association constant (1/ a) is the equilibrium dissociation constant for the drug-protein complex ... 

It is important to notice that the association constants decrease with salt concentration at low ionic strength in the Debye-Htickel approximation [55], but at high ionic strength they tend to a constant [46]. At the same time, the complex fraction always increases with salt concentration. The absence of resolubilization is the signature of a dominant dicomplexation. In contrast, if the monocomplexation is dominant, precipitation is expected to be followed by a resolubilization due to charge inversion [20],... 

The above equation is the law of mass action as applied to reaction (3.1). Recall that constant Kd s. called the dissociation constant, while its inverse Ka = is called the association constant (Houston 2001). 

Stability constants as a function of temperature and the calculated complexation enthalpies and entropies of the associated reactions are given in Table II. The results of duplicate experiments at 2.0 M acidity and ionic strength are shown as the last entry in the table. Comparison of the results at 25°C, and 1.0 and 2.0 M acidity indicate an approximate inverse first order stoichiometry in [IT "] for the Kj and acid independence for K2. 

Pult+, and HSOIJ, this result combined with our results at 1 M acidity indicates an inverse first power stoichiometry in [H+] for the 1 1 complex, and acid independence in the formation of the second complex. If we assume n = m 1 in equation 2, the equilibria and associated stability constants in this system are... 

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