Thermodynamic lead-small molecule interactions

Very recently, the kinetics and thermodynamics of a variety of axial ligation reactions have been investigated with Fe11 and Co11 porphyrins involving the small molecules CO, 02, and NO as ligands 27-30, 40, 92, 93). These experiments lead to the conclusion that the dynamic trans effects observed in these systems cannot alone be explained by the interaction models D and F (Fig. 1). Especially imidazole and its derivatives do not hold the place in various series of trans effects that they should take on the ground of their proton basicities. Therefore, besides their usual a-donor-tr-acceptor function, these unsaturated molecules are ascribed an additional 7r-donor function. 

The introduction of a relevant expression for the critical determinant in the mean-field lattice gas model for binary systems is discussed here. It leads to an alternative and thermodynamic consistent method of adjusting two-particle interaction functions to experimental critical binary 1iquid-vapour densities. The present approach might lead to new developments in the determination of MFLG parameters for the mixture in small-molecule mixtures and in polymer solutions and polymer mixtures (blends). These relevant critical conditions appear because of the extra constraint, which is the equation of state, put on the hole model, and are... 

DilP recently discussed the merits and limitations of models that assume thermodynamic additivity and independence (of energy types, of neighbor interactions, of conformational freedom, of monomer contact pairing frequencies, etc.). He states that biological molecules may achieve stability in the face of thermal uncertainty, as polymers do, by compounding many small interactions this summing can stump modelers because application of the additivity principle leads to accumulated error. Entropies and free energy may not be additive to describe weak interactions that are ensembles of states. He concludes that additivity principles appear to be few and limited in scope in biochemistry. 

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