MAP_CHANNELS: a computation tool to aid in the visualization and characterization of solvent channels in macromolecular crystals

A computation tool is described that facilitates visualization and characterization of solvent channels or pores within macromolecular crystals. A scalar field mapping the shortest distance to protein surfaces is calculated on a grid covering the unit cell and is written as a map file. The map provides a multiscale representation of the solvent channels, which when viewed in standard macromolecular crystallographic software packages gives an intuitive sense of the solvent channel architecture. The map is analysed to yield descriptors of the topology and the morphology of the solvent channels, including bottleneck radii, tortuosity, width variation and anisotropy.