Why do aromatic amino acids absorb UV light?

Why do aromatic amino acids absorb UV light?

Due to the presence of tyrosine and tryptophan, proteins and peptides containing these aromatic amino acids absorb UV light at a wavelength of 280 nm. Each of these residues has distinct absorption and emission wavelengths and varies in quantum yields.

Which aromatic amino acid absorbs the least amount of UV light?

The absorbance of ultraviolet light by tryptophan is greatest, that of tyrosine is less, and that of phenylalanine is least. If the tyrosine or tryptophan content of the protein is known, therefore, the concentration of the protein solution can be determined by measuring its absorbance between 280 and 290 nanometres.

Which amino acid absorbs UV light?

There are two amino acids that are primarily responsible for the UV absorbance of proteins: tyrosine and tryptophan.

Which amino acid absorbs at 280 nm?


Absorption Fluorescence
Amino Acid Wavelength (nm) Quantum Yield
Tryptophan 280 0.20
Tyrosine 274 0.14
Phenylalanine 257 0.04

What increases the fluorescence of aromatic compounds?

Fluorescence and Structure Most unsubstituted aromatic hydrocarbons fluoresce in solution too. The quantum efficiency increases as the number of rings and the degree of condensation increases.

Do aromatic compounds have Colour?

The sp2 hybridized ring atoms are connected by brown bonds, the π-electron pairs and bonds that constitute the aromatic ring are colored blue. Electron pairs that are not part of the aromatic π-electron system are black.

Which are the tests to identify aromatic amino acids?

Xanthoproteic test is used to detect amino acids containing an aromatic nucleus (tyrosine, tryptophan and phenylalanine) in a protein solution which gives yellow color nitro derivatives on heating with conc. HNO3.