MainChain is a very simple extension that undisplays all atoms except for those named N, CA, and C. These atoms typically form the main chain of a peptide or protein.
Mainchain is an extension in the Utilities category. There are several ways to start an extension. The user may be asked to confirm whether MainChain should be executed (this can be turned off in the General preferences). MainChain undisplays all atoms except for those named N, CA, and C. The Python code is shown in the Programmer's Guide example Molecular Editing Using Python.