International
Tables for Crystallography Volume F Crystallography of biological macromolecules Edited by M. G. Rossmann and E. Arnold © International Union of Crystallography 2006 |
International Tables for Crystallography (2006). Vol. F. ch. 24.3, p. 664
Section 24.3.2.4. 2D chemical connectivity data
a
Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, England |
The formal two-dimensional chemical structural diagram for each entry (Fig. 24.3.2.2) is encoded in the form of a compact connection table. Chemical connectivity is recorded in terms of a set of atom and bond properties. The atom properties recorded are: atom number, element type, number of connected non-H atoms, number of terminal H atoms and the formal atomic charge. Bond properties are encoded as a pair of atom numbers and the formal chemical bond type that connects those atoms. Bond types employed in the CSD connectivity descriptions are: single, double, triple, quadruple (metal–metal), aromatic, delocalized double and π bonds. Bond types are (automatically) coded negative if the bond forms part of a cyclic system.