Schellman Loop

Motif Glossary

Schellman Loop


Our selection of Schellman Loops is on the basis of a motif of seven consecutive residues in which there is:

The standard definition is of a 6-residue motif, excluding residue‑1. Residue-1 is included here as it is involved in an additional hydrogen bond (illustrated) found in 96% of 4,5-αRαR Schellman loops in the database. A revised definition of the Schellman loop would include:

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These encompass the following conformations:

The two possible additional bonds are not designated as sub-categories as there is a continuum of structures between them.


Schellman, in Protein Folding, Ed. Jaenicke, 53-61 (1980)


1. There is also a rare ‘wide’ variant (one residue longer) which is not included here.

2. Other additional hydrogen bonds are found in particular cases.

3. The Schellman Loop is also known as the ‘Paperclip’.


1. Schellman Loops are a common feature of the C-termini of α-helices, where the αL conformation — always found at residue-6 — breaks the helix.

2. The 4,5-βRαL and 4,5-βLαR forms, although included for completeness, are not found in the database, and the 4,5-αLαL form is rare.