Hairpin
From Eterna Wiki
Hairpin
<img id="docs-internal-guid-5e53c45a-08b6-eda7-7ae6-6a8439d67d0e" style="float: right;" src="https://lh4.googleusercontent.com/ObrCwwAThPbapYOIatV27aLJPqu1SEmsXjeS1VsOQebAjae4aBYL3NN7o2qO8Y05_qwscaIio8TQ0pOCbkKs-u2QWlnC2f5v5fLzciLVv5wv8gyssD7FpsFxGvkHFJ4" alt="" width="192px;" height="94px;" />Lollipop-shaped structure. (Wikipedia)