Backbone representations

Protein Main Chain

Here is a small alpha helix (15 amino acids)^[1] In the , all atoms are shown, colored by element: C H O N.

• First, we'll simplify by . Hydrogen atoms make up almost exactly 50% of the atoms in proteins.

• Next, we'll simplify by . What remains is called the main chain. Each amino acid's main chain atoms are N-C-C, where the first C is the alpha carbon (shown as a ball), and the second, the carboxyl carbon with its double-bonded oxygen (double bonds not shown). We could also , leaving only the atoms that are part of the main chain, also called the backbone.

Protein Backbone Trace

Backbone Trace