The new CCP4 Coordinate Library as a toolkit for the design of coordinate-related applications in protein crystallography.

The new CCP4 Coordinate Library is a development aiming to provide a common layer of coordinate-related functionality to the existing applications in the CCP4 suite, as well as a variety of tools that can simplify the design of new applications where they relate to atomic coordinates. The Library comprises a wide spectrum of useful functions, ranging from parsing coordinate formats and elementary editing operations on the coordinate hierarchy of biomolecules, to high-level functionality such as calculation of secondary structure, interatomic bonds, atomic contacts, symmetry transformations, structure superposition and many others. Most of the functions are available in a C++ object interface; however, a Fortran interface is provided for compatibility with older CCP4 applications. The paper describes the general principles of the Library design and the most important functionality. The Library, together with documentation, is available under the LGPL license from the CCP4 suite version 5.0 and higher.