Calculated relative binding enthalpies

Table 1. Inhibition of sialidase from influenza virus A/N2 by three transition state analogs and calculated relative binding enthalpies. Calculated results were obtained using molecular mechanics derived nonbonded interaction energies (MM energies) and a continuum electrostatics approach (CE energies).

Belleau (293) calculated entropies and enthalpies of binding to acetylcholinesterase for a homologous series of alkyltrimethylammo-nium compounds RN (0113)3, where R = CH3 through n-CigHjs. The observed relative potencies in the series were rationalized on the basis of hydrophobic bonding phenomena coupled with the ability of the alkyl chains to displace ordered water from the acetylcholinesterase surface. 

Head et al. developed a PLS-based model VALIDATE [47] to scale the relative contributions of entropy and enthalpy to binding affinity for a variety of complexes whose crystal structures had been determined. Molecular mechanics were used to calculate several parameters most correlated with enthalpy of binding, while changes in surface area, number of rotatable bonds fixed upon binding and other parameters more related to the entropy of binding were also included in the model. Of interest was that the principal components of the model were dominated by two terms (AH and AS,... 

Figure 9 The H2 adsorption energy as calculated by ADF vs H coverage (Hn/Pt4 cluster) for the acidic and basic supports (acidic solid squares and solid lines, basic open triangles and dashed lines). In a H2 atmosphere at low temperature, all H2 that has a exothermic (negative) adsorption enthalpy binds to the Pt, and the predicted coverage (H/Pt4) is shown on the x-axis. 2) Upon evacuation at high T (eg. 323 K), only strongly adsorbed H2 with a large exothermic adsorption enthalpy (< -75 kJ/mol) remains on the surface. The amount of weakly adsorbed H2 is relatively small for basic supports.

Depending on the type of interaction between an adsorbed particle and a solid state surface there are cases, where adsorption enthalpies can be calculated using empirical and semi-empirical relations. In the case of atoms with a noble-gas like ground-state configuration and of symmetrical molecules the binding energy (EB) to a solid surface can be calculated as a function of the polarizability (a), the ionization potential (IP), the distance (R) between the adsorbed atom or molecule and the surface, and the relative dielectric constants (e) (Method 9) [58-61] ... 

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