CAMM electrostatic models

The marching-cube algorithm has been used also by Kolle and Jug (1995) to define the tesserae of isodensity surfaces. The procedure is implemented in the semiempirical SINDOl program (INDO with Slater-type orbitals, Li et al., 1992). To compute AS charges the asymptotic density model ADM (Koster et al., 1993) is used. This is an approximation to the calculation of molecular electrostatic potentials based on the cumulative atomic multipole moment procedure (CAMM, Sokalski et al., 1992). 

Function e provides a critical test for the approximate charge distribution model related to real applications. As the first example, we used imidazole, which frequently models histidine residue. In the Table 3 we compare results obtained for four different molecular charge density models Mulliken [27], CHELP [28] and ESP [29] charges and CAMM (up to quadruples). In general, electrostatic potentials on solvent accessible surfaces described by CAMM series truncated at quadrupole term tend to perform slightly better s = 2-10% than those calculated using potential-derived atomic charges. 

These results may partly validate discrete solvation models, where environmental effects are mainly represented by electrostatic effects. In both complexes correlation term as well as three- or four- body effects due to additional solvent molecules are negligible. More approximate results could be obtained using Effective Fragment Potentials AEefp [31] or CAMM estimate Eel,mtp ... 

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