Practice question

Proteins display two principal UV absorption envelopes due to distinct chromophores. Aromatic residues phenylalanine, tyrosine, tryptophan absorb near 280 nm via π→π* transitions. Peptide backbone containing amide carbonyl undergoes separate transitions: intense π→π* around 190 nm and weaker n→π* shoulder near 210-220 nm. Maximum near 210 nm often used for peptide bond detection independent of aromatic content, valuable for peptides lacking tryptophan and tyrosine, quantifying number of peptide bonds. Absorbance at 210 nm complements A280, enabling total protein assessment and HPLC detection of eluting peptides with high sensitivity.