In GChemPaint, Residues are atoms groups with a symbol, such as Ph for phenyl. GChemPaint comes with a list of predefined group symbols, but you can define new residues in needed. When importing a file with unknown symbols, either a GChemPaint file, or a ChemDraw® file, new symobls are added to the user define symbols list.
To define a new symbol, choose, the following dialog will pop up:
You can choose either a new residue (the default) or an already known symbol in the dropdown list at top left of the dialog box. Selecting "Ph" leads to:
The entries and the check box are greyed because this residue is standard and can't be edited.
The name must be unique, but several symbols can be defined. The various symbols must be separated by semicolons. Generic residues correspond to symbols which may represent various structures such as R for alkyle, Ar for aryle, X for a halogen atom, or M for a metal atom.
If you display the structure page for the phenyl aresidue, you get:
The bullet represents the attachment point of th residue. It is linked to the first atom by a single bond. Multiple bonds are not allowed in this version of GChemPaint.
When you want to create a new residue, you might first select an existing one with a similar structure. When you select "New" in the list, the structure is conserved. When the dialog box is created, the default structure is a methyl. For generic residues the structure should represent a simple case.
When you have the new strucutre and filled the name and symbol for it, you have to click on thebutton to save it to the database.
Thebutton is used for removing the selected residue from the database and is enabled only when the residue can be securely deleted.