The X-Pol theory, first introduced in 1997, is both a fragment-based electronic structure method and a quantal force field for macromolecular systems.

    A New Paradigm for Biomolecular Simulations

Molecular mechanics dates back to the pioneering studies of steric effects independently by Hill and by Westheimer, whereas the force field for biomolecular simulations was established by Lifson in the 1960s. Tremendous progress has been made in the past fifty years; however, a sobering fact is that the basic functional form, including polarization terms, has hardly changed. A fundamental change in force field development is warranted in order to increase the predictability of computational biology.

In the X-Pol potential, the system is treated explicitly by electronic structure theory and the wave function (or electron density) is optimized by self-consistent field (SCF) method. The internal energy terms and electrostatic potentials used in classical force fields are replaced and described explicitly by electronic structure theory. Naturally, electronic polarization and charge transfer are treated by the theory. Furthermore, such a method can be directly used to model chemical reactions, electron transfer, and electronically excited states.

The X-Pol potential for macromolecular simulations is being developed collaboratively between the groups of Professor Gao and Professor Don Truhlar. The feasibility of the X-Pol potential for modeling biomolecular systems has been recently demonstrated.

              WB01622_.gif (155 bytes)      Theory

              WB01622_.gif (155 bytes)      Applications