Protein Chemistry: Structure, Properties, and Research Methods - Shendryk, A. N. 2022

Amino Acids
Amino Acids
Electronic Absorption Spectra and Acid-Base Properties of Amino Acids in Solutions

Electronic Absorption Spectra

All Amino Acids absorb light in the far ultraviolet region (< 220 nm). In the UV region, light is absorbed by three of the 20 standard Proteinogenic Amino Acids: Tyrosine, Tryptophan (λmax – 280 nm), and phenylalanine (λmax – 260 nm) (see Fig.). Most Proteins contain tyrosine residues, which serves as the basis for a rapid and convenient analysis using UV spectroscopy.

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Cysteine exhibits weak absorption at 240 nm (due to the presence of a disulfide group).



Last update: 06/08/2026

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