Binding constants sigmoidal

Thus, for haemoglobin (Hb) the oxygen binding curves are sigmoidal as is shown in the above figure. The fact that n exceeds the unit can be ascribed physically to the fact that attachment of 02 to one haem group increases the binding constant for the next 02, which in turn increases the constant for the next one and so... 

The sigmoid binding curve of any allosteric protein can be calculated by using just three parameters L, the allosteric constant, which is equal to the ratio [T]/[R] for the unligated states and KT and KR, the dissociation constants for each site in the T and R states, respectively. 

Hemoglobin (Hb) behaves differently. Its sigmoidal binding curve can be fitted by an association-constant expression with a greater-than-first-power dependence on the oxygen concentration ... 

Kmi would be the standard Michaelis constant for the binding of the first substrate, if [ESS] = 0. Km2 would be the standard Michaelis constant for the binding of the second substrate, if [E] = 0 (i.e., the first binding site is saturated). In the complete equation, these constants are not true Km values, but their form (i.e., Km] = (k2 + k25)/k 2) and significance are analogous. Likewise, k25 and k35 are Vmi/Et and Vm2/Et terms when the enzyme is saturated with one and two substrate molecules, respectively. Equation (10) describes several non-Michaelis-Menten kinetic profiles. Autoactivation (sigmoidal saturation curve) occurs when k35 > k24 or Km2 < Km 1, substrate inhibition occurs when k24 > 35, and a biphasic saturation... 

In polyionic complexes, formed by polymeric amines and sodium oligophosphates, an sigmoid dependence of the effective constant of binding on oligomer length is observed (Fig. 24). The critical degree of polymerization of is equal to 792 for the system sodium polyphosphate-poly(dimethylaminoethyl methacrylate). It should be... 

---