Question

Which of the following peptides do/does NOT absorb ultraviolet light above 250 nm wavelength?

• A. MQRTVWG
• B. YDEIGVL
• C. PLASNGK
• D. GSQTKRL

Hint:

Peptides that absorb UV light above 250 nm typically contain aromatic amino acids like tryptophan (W), tyrosine (Y), or phenylalanine (F). Peptides without these residues do not absorb UV light in this range.

Answer 1

The Correct Option is C, D

Peptides absorb ultraviolet (UV) light at wavelengths around 280 nm due to the presence of aromatic amino acids like tryptophan, tyrosine, and phenylalanine. When examining peptides for UV absorbance, we look for these aromatic residues.
- (A): MQRTVWG contains tryptophan (W), which absorbs UV light around 280 nm. Thus, it does absorb UV light above 250 nm. Hence, statement (A) is incorrect.
- (B): YDEIGVL contains tyrosine (Y), which absorbs UV light around 280 nm. Thus, it does absorb UV light above 250 nm. Therefore, statement (B) is incorrect.
- (C): PLASNGK does not contain any aromatic residues. Therefore, it does not absorb UV light above 250 nm. Hence, statement (C) is correct.
- (D): GSQTKRL does not contain any aromatic residues either. Hence, it does not absorb UV light above 250 nm. Therefore, statement (D) is correct.
Thus, the correct answers are (C) and (D).