Overall binding constants

Overall, it is seen that the binding constants in presence of counterions (total buffer concentration of 20 mM) are lower by a factor of about 10 than in a plain methanolic medium without counterions (see Table 1.4). In contrast, the intrinsic enantioselecitivity is still in the same order of magnitude or even higher (A s/A r 17 by ITC and ca. 50 under CE conditions) because of a more proper balance of the otherwise dominating ionic interaction. 

Ackers et al. (1982, 1986) analyzed data on the binding of the X repressor to the left and right operators obtained by footprinting titration. In order to obtain the correlations in this system, they wrote the following relations between the (overall) macroscopic binding constants Ki (i = 1,2, 3), defined in Section 2.3, and the intrinsic binding constants kf, and k ... 

Figure 5, where we compare the binding of Cj Py in the presence of 0.01 m NaCl to PAA, pectate and alginate. We note that the order of the overall binding constant Ku, defined by (2,11,12,16) varies... 

The influence of the head group, i.e. pyridinium or trlme-thylammonium, on the overall binding constant Ku and the coopera-tivity parameter u is relatively small. It is perhaps surprising that in all cases Ku for the pyridinium salt is larger than for the trimethylammonlum salt, as can be seen best e.g. by comparing C] Py" and TTA" ", just as the cmc for pyridinium salts is always lower than the cmc of the corresponding trlmethylammonium salt. 

SL,SL2,...,SLp. DeLning overall binding constant, wherei = 1 to n, and substituting into the mass balance expression for substrate in the usual manner gives the following equation ... 

The secondary bonds, which may be formed much more slowly than the primary bonds, actually contribute more to the overall affinity. For example, the primary (Coulombic) bond between bovine serum albumin (BSA) and anti-BSA IgG is 3.3kcalM 1 whereas the secondary bond (van der Waals) is 28kJ, for a total AH = 42 kJ. Because the formation of the secondary bond is much slower, it is easier to prevent formation of the strong complex rather than to try to dissociate it. This is one reason why the competitive immunoassays yield results that correlate with the equilibrium-binding constants, but any such direct-binding assays have to rely on the measurement of the initial rate of binding. 

In these circumstances, an overall binding constant, fin may be defined for the overall process, the individual if values are then known as the stepwise binding constants ... 

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