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Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
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The property of protein to absorb UV rays of light is due to:
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The correct answer is  Aromatic amino acids:-
Amino Acid Absorb UV Light: 
Amino Acids which absorb 250-290 nm (Maximum at 280 nm) UV light are tryptophan, phenylalanine, tyrosine. Maximum absorption of UV light by tryptophan. 
Remember: 

Aromatic amino acids absorb UV light. 
Amino acids are colorless because, they do not absorb visible light.