Intrinsic fluorescence of protein is due to
(1) aromatic amino acids
(2) sulphur-containing amino acids
(3) histidine
(4) proline
The correct answer is:
(1) Aromatic amino acids
Explanation:
Intrinsic fluorescence in proteins mainly arises from the aromatic amino acids: tryptophan, tyrosine, and phenylalanine.
Tryptophan is the primary contributor due to its high quantum yield and sensitivity to its environment, making it the most useful intrinsic fluorescent probe in proteins.
Although tyrosine and phenylalanine also contribute, tryptophan generally dominates the fluorescence signal.
Histidine is aromatic but contributes very little to fluorescence, and sulphur-containing amino acids (like cysteine and methionine) and proline do not significantly fluoresce.
Thus, the intrinsic fluorescence of proteins is attributed to aromatic amino acids.
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