The beta hairpin (sometimes also called beta-ribbon or beta-beta unit) is a simple protein structural motif involving two beta strands that look like a hairpin. The motif consists of two strands that are adjacent in primary structure, oriented in an antiparallel direction (the N-terminus of one sheet is adjacent to the C-terminus of the next), and linked by a short loop of two to five amino acids. Beta hairpins can occur in isolation or as part of a series of hydrogen bonded strands that collectively comprise a beta sheet.
Researchers such as Francisco Blanco et al. have used protein NMR to show that beta-hairpins can be formed from isolated short peptides in aqueous solution, suggesting that hairpins could form nucleation sites for protein folding.[1]