Molecular Lipophilicity Potential

Approaches to display and analysis lipophilic/hydrophilic properties on molecular surface are studied for characterization of the surfaces of proteins by means of local lipophilicity. Audry et al. (Audry et al., 1986) introduced the name ‘molecular lipophilicity potential’ (MLP) and postulated a functional form

Where is the partial lipophilicity of the -th atom of a molecule and is the distance of the measured point in 3D space from atom . Since a long-range distance dependency of the individual potential contributions may lead to overcompensation of local effects, Heiden et al. (Heiden et al., 1993) proposed another MLP approach called MHM (Molecular Hydrophobic Mapping) and used a Fermi type distance function

where a proximity distance of = 4Å and = 1.5 are used, is the partial lipophilicity of the -th atom of a protein and is the distance of the surface point in 3D space from atom . All atoms which are further away from the surface point do not contribute significantly. HINT program (Kellogg et al., 1991) provided another approach to display and analysis lipophilic/hydrophilic properties on protein surface considering the solvent accessible surface area

where is the solvent accessible surface area for atom , is the hydrophobic atom constant for , and is the distance function and always defined as . Although the MLP functions defined above are not based on a rigorous physical concept, however, for the visualization of lipophilicity values on a molecular surface, those functions generate reasonable data for all surface points.

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