RasMol atom expressions may contain predefined sets. These sets are single keywords that represent portions of a molecule of interest. Predefined sets are often abbreviations primitive atom expressions, and in some cases of selecting areas of a molecule that could not otherwise be distinguished. A list of the currently predefined sets is given below. In addition to the sets listed here, RasMol also treats element names (and their plurals) as predefined sets containing all atoms of that element type, i.e. the command select oxygen is equivalent to the command select elemno=8.
AT Acidic Acyclic
Aliphatic Alpha Amino
Aromatic Backbone Basic
Bonded Buried CG
Charged Cyclic Cystine
Helix Hetero Hydrogen
Hydrophobic Ions Large
Ligand Medium Neutral
Nucleic Polar Protein
Purine Pyrimidine Selected
Sheet Sidechain Small
Solvent Surface Turn
Water