A computer-readable dictionary for protein structure refinement is pre
sented. The dictionary is based on the set of interatomic bonds and bo
nd angles previously derived from small-molecule structures by Engh &
Huber [Acta Cryst. (1991), A47, 392-400]. The internal inconsistency o
f the set is discussed. Some preliminary results derived from several
protein structures refined at atomic resolution are compared with this
set.