GRASP is a graphics program written for Silicon Graphics computers that is widely used by the structural biology community to visualize macromolecules. Its particular strengths compared to other such programs is its facility with surfaces and with electrostatics. The program contains extremely rapid algorithms for the construction of rendered molecular surfaces and for solving the Poisson-Boltzmann equation. The latter enables a description of the electrostatic field generated by charges within a molecule (typically assigned to atom centers) such that the difference in dielectric between water (dielectric = 80) and the molecule (dielectric = 4), and also the influence of mobile ions (salt), is taken into account. There is now considerable experimental evidence that such a description has physical validity.
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Last modified: 12/27/06