6.6 Dude, where's my SD Data?

SD tag data can be set to OEMolBases , OEMCMolBases , or OEConfBases . Generally, OEChem will never lose any data when reading or writing. However, there are constraints placed on OEChem as to where the data must go based upon the file format being used.

A problem occurs when setting SD tag data to an OEMCMolBase and then writing it to SDF. SDF files do not support multiple conformers. However, OEChem can automatically read consecutive conformers out of a SDF file into a OEMCMolBase . To preserve the generic data OEChem has no choice but to push the data onto the conformers.

OEB files do not have this restriction upon them because they do support multi-conformer molecules. The following table shows how to round trip SD tag data through the SDF and OEB formats.

Attached To	Written To	Read Into	Attached To
`OEMCMolBase`	sdf	`OEMCMolBase`	`OEConfBase`
`OEMCMolBase`	sdf	`OEMolBase`
`OEMCMolBase`	oeb	`OEMCMolBase`
`OEMCMolBase`	oeb	`OEMolBase`
`OEConfBase`	sdf	`OEMCMolBase`	`OEConfBase`
`OEConfBase`	sdf	`OEMolBase`
`OEConfBase`	oeb	`OEMCMolBase`	`OEConfBase`
`OEConfBase`	oeb	`OEMolBase`
`OEMolBase`	sdf	`OEMCMolBase`	`OEConfBase`
`OEMolBase`	sdf	`OEMolBase`
`OEMolBase`	oeb	`OEMCMolBase`	`OEConfBase`
`OEMolBase`	oeb	`OEMolBase`

Practically speaking, it is best to never attach SD tag data to an OEMCMolBase . This should only be done as a space optimization when it is assured that the multi-conformer molecule will only be written to OEB.

To this end, when an OEMol copy constructs from an OEGraphMol the SD tag data (and any other generic data) is attached to the first conformer.

				OEChem - Python Theory Manual

				OEChem - Python Theory Manual