Cyclisation joins two points of a peptide chain: the N- and C-termini (head-to-tail), a side chain to a terminus, two side chains (for example by a lactam bridge), or two cysteines through a disulfide bond. The ring restricts the backbone's conformations and usually makes the peptide more resistant to exopeptidases.
A cyclic peptide and its linear precursor can have nearly the same mass, so cyclisation is usually confirmed by a combination of mass spectrometry and a shift in HPLC retention time.
See also
For in vitro laboratory research only. Not for human or veterinary use. This library describes chemistry, analytical methods and published laboratory research; it gives no guidance on use in people or animals.