eduSoft, LC and OpenEye Scientific Software are jointly producing SGI versions of release (1.0) of Open Eye's state-of-the-art Poisson-Boltzmann electrostatic code Zap.

We have made Zap available as a tool for serious molecular modeling within the Sybyl commercial modeling suite.

Zap has a variety of unique capabilities: calculation of atom potentials from partial charges, calculate small molecule and macromolecule solvation energies, create electrostatic contour maps, technology for estimating pKas of protein residues, a unique algorithm for estimating ligand binding energies, methods for finding optimal charges in a molecule, and new electrostatic surface and volume descriptors.

Zap and 3D QSAR

One of the unique features of Zap is the simple introduction of the Zap Potential maps into 3D QSAR. We have performed some preliminary computational experiments with the Zap field within CoMFA (Sybyl) and have found the Zap Potential field to correlate better with activity than the basic standard electrostatic field. Following are results from two commonly available data sets:

data set

Zap Potential q2 (components)

CoMFA electrostatic q2 (components)

21 steroids (R.D. Cramer)

0.827 (3)

0.765 (4)

26 D2 agonists (Y.C. Martin)

0.330 (5)

-0.078 (1)

Experiments were performed using SAMPLS with typical 2A grid spacing; the Zap field was applied with a 30 kT cutoff for grid points within the molecule; the CoMFA electrostatic field was applied with a 30 kcal/mol cutoff.