Ribclass sets residue class: which atoms in a residue control ribbon path and which are considered part of the backbone. The class-name can be none, indicating default behavior, or the name of a residue class previously created and named with Ribbon Style Editor. The default behavior is to use the built-in residue class most appropriate for a given residue, based on the atoms it contains. Residue class names containing spaces should be enclosed in single or double quote marks, for example:
ribclass "beta peptide" :1-8.bResidues with any atoms in atom-spec will be affected.
The command ribspline sets how ribbon path is calculated from atom positions. Backbone atoms are hidden when ribbon is shown unless ribbackbone is used.