MEPSIM - A COMPUTATIONAL PACKAGE FOR ANALYSIS AND COMPARISON OF MOLECULAR ELECTROSTATIC POTENTIALS

MEPSIM is a computational system which allows an integrated computatio n, analysis, and comparison of molecular electrostatic potential (MEP) distributions. It includes several modules. Module MEPPLA supplies ME P values for the points of a grid defined on a plane which is specifie d by a set of three points. The results of this program can easily be converted into MEP maps using third-parties graphical software. Module MEPMIN allows to find automatically the MEP minima of a molecular sys tem. It supplies the cartesian coordinates of these minima, their valu es, and all the geometrical relationships between them (distances, ang les, and dihedral angles). Module MEPCOMP computes a similarity coeffi cient between the MEP distributions of two molecules and finds their r elative position that maximizes the similarity. Module MEPCONF perform s the same process as MEPCOMP, considering not only the relative posit ion of both molecules but also a conformational degree of freedom of o ne of them. The most recently developed module, MEPPAR, is another mod ification of MEPCOMP in order to compute the MEP similarity between tw o molecules, but only taking into account a particular plane. The latt er module is particularly useful to compare MEP distributions generate d by pi systems of aromatic rings. MEPSIM can use several wavefunction computation approaches to obtain MEP distributions. MEPSIM has a menu type interface to simplify the following tasks: creation of input fil es from output files of external programs (GAUSSIAN and AMPAC/MOPAC), setting the parameters for the current computation, and submitting job s to the batch queues of the computer. MEPSIM has been coded in FORTRA N and its current version runs on VMS/VAX computers.