Thermodynamics membrane-water partitioning, with

Based on thermodynamic arguments, it has been suggested that octanol does not accurately represents fish lipids [81]. Lipid solubility has been proposed as an additional parameter based on the argument that lipids are more structured than octanol [82]. Partition coefficients with other solvents (triolein-water) and membrane vesicles are measured and related to as well as to BCF [32, 83, 84]. In general, these latter partition coefficients fairly correlate with Kq with systematic lower values at high These differences may lead to an apparently lower BCR The consequences are that overestimates bioaccumulation for very hydrophobic compounds. 

Such structural models, however are hardly compatible with a lateral penetration of peptide ligands as required in a membrane-bound pathway c . he hormone/receptor recognition and binding process. Experimental evidences for such mechanism are difficult to produce, since in the partition equilibrium of hormones between the water and the lipid phase occupation of the receptor from the extracellular phase cannot be excluded. However, with an escape of the peptide ligands into the water phase and subsequent direct collision with the receptor binding site all the thermodynamic and conformational advantages of an accumulation at the membrane surface would be lost. 

The vdWP theory with a set of the independent variables necessarily requires semipermeable membrane to separate water from the guest fluid, hence the pressure Pg of the fluid phase is different in general from the pressure p of the hydrate phase. The appropriate thermodynamic potential is derived in Section II.B. In the light of the phase rule and the experimental conditions, it is desirable to alternate the ensemble to meet the thermodynamic potential F [30,31]. The partition function S is converted into the generalized partition function T as... 

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