Random Research highlight: Delaunay tesselation of proteins: Triangulations on the plane are frequently used for discretizing geometrical data and relations. Delaunay triangulations are of special importance, since they can be generated easily and the resulting triangles are usually not far from the regular triangles. In discretizing spatial data of protein-ligand complexes we need the three-dimensional analogue of the triangulations. Here we are applying Delaunay decomposition for all the heavy atoms of 3D protein structures, and identify those tetrahedra which contain atoms from bound ligands. Next we classify the tetrahedra according to the atoms in their vertices, and by the atoms of the ligands the convex hull these tetrahedra contain. Our main result is the analysis of the frequencies of the separate ligand atoms in different types of tetrahedra, formed from protein atoms. BMC Bioinformatics, 2008, 9(Suppl 1):S11.