Theoretical models of binding

These stand head and shonlders above the non-specific background, a bit like spectral peaks projecting above background noise. Specific binding events are the cornerstone of chemical biology. 

In order to measure any constant, we need an equation that relates this constant to variables that maybe determined by experiment. For a single-site, single-affinity binding model, there is a relatively simple way of deriving such an equation. If we define total concentration of receptor [R]o according to 

SO that total receptor concentration is a sum of the concentrations of ligand bound and ligand free states, if we now substitute for [R] from Equation (7.17) then we achieve the following  

Finally, let us introduce B, which represents the number of moles of ligand L bound per mole of receptor R (B may also be defined as the combined mole fraction of ligand L bound to receptor). This is given mathematically by the simple ratio represented by 

Substituting for [RL] from Equation (7.21) then gives us the following expression that happily relates to experimental variables  

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Now that we have covered the main theoretical models of binding and molecular recognition events, including their analytical equations and equilibrium binding constants, we must show that equilibrium binding constants can be derived from the experimental equivalents of B and [L]. 

The scorpion a-toxins have been shown to bind to site 3 on the voltage-gated sodium channel [24,27,42]. These polypeptides contain up to 70 residues crosslinked by four disulfide bonds, but show no sequence similarity to the anemone polypeptides. Possible structural similarities have been discussed [24], and in a theoretical model of the anemone toxin Bg II, some of the cationic residues were in similar locations to those in the crystal structure of the scorpion toxin Aah II [26]. 

Simultaneously, with the application of the latest experimental techniques, some new theoretical models of edl were constructed. They describe the electric charge and potential distribution in the interfacial region and fit to the experimental data. The new models replace the old classic ones that could not predict some observed parameters from measured ones. Some models, characteristic for metal oxide-electrolyte solution were constructed a porous layer model, then a site binding model and its successive version. 

The breaking and/or formation of bonds involving TMs is an integral part of most elementary steps in TM chemistry. A theoretical model of practical use in this area must therefore be able to describe such bond energies with sufficient accuracy. In addition, reliable computational data on TM binding energies are important in their own right, because only a limited... 

The researchers noted that the theoretical model of the end-on terminal binding through the N (rather than 0)-atom is more consistent with the experimental spectroscopic data mode. The studies also revealed that Ru"-N20 bond is dominated by 7i back-donation, which, however, is weak compared to that found in the corresponding known ruthenium-nitrosyl complex. See further discussions below for possible bridge binding of N2O in a copper enzyme. 

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