Atomic accessible and contact surfaces as restraints in the Hendrickson & Konnert refinement program

A computer algorithm is presented for calculating and, if required, optimizing the extent of atomic areas in a molecule that are accessible to the solvent or in contact with non-solvent atoms either from the same or from another molecule. The algorithm has been implemented as new restraints in a modified version of the least-squares refinement program of Hendrickson & Konnert [In Computing in Crystallography (1980), edited by R. Diamond, S. Ramaseshan & K. Venkatesan, pp. 1301-1325. Bangalore: Indian Academy of Sciences]. Information on the correctness of atomic interactions in a given configuration can thus be used either as added data during the crystallographic X-ray refinement or, independently, in the analysis and modeling of molecular structures. The algorithm appears well suited for studying the structure and interactions of proteins and nucleic acids.