Treatment of intermolecular contacts in the restrained refinement program of Hendrickson & Konnert

The restrained reciprocal-space least-squares refinement program of Hendrickson & Konnert [Computing in Crystallography, edited by R. Diamond, S. Ramaseshan & K. Venkatesan, pp. 13.01–13.25. (1980). Bangalore: Indian Academy of Sciences] has been modified to include non-bonded and/or hydrogen-bonded contacts between molecules related by symmetry operations and/or unit-cell translations. The modified program has been tested on an inhibited form of aspartate aminotransferase, which is an α₂ dimeric enzyme with a crystallographic twofold axis relating the subunits. A number of heretofore unseen close contacts between atoms of separate subunits were located and correctly dealt with by the modified program.