#Id: 8444
#Unit 1. Molecules and their Interaction Relevant to Biology
Both the pi helix and the 310 helix occur rarely and usually only at the ends of a helices or as single-tum helices. They are not energetically favorable, since the backbone atoms are too tightly packed in the 310 helix and so loosely packed in the n helix that there is a hole through the middle.
Only in the a helix are the backbone atoms properly packed to provide a stable structure.
