A peptide bond forms when the carboxyl group of one amino acid and the amino group of the next condense with loss of water. The bond is planar and rigid because of partial double-bond character, which shapes the backbone's conformations.
Its absorbance in the far ultraviolet, strongest below about 220 nm, is why HPLC detection of peptides is usually set at 214–220 nm.
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.