Question

Pick the most basic dipeptide from the following:

• A. Gly-Glu
• B. Gly-Lys
• C. Gly-Arg
• D. Gly-His

Hint:

Basicity Order: Arginine $>$ Lysine $>$ Histidine. Remember "Arg" is the strongest!

Answer 1

The Correct Option is C

Step 1: Concept
The basicity of a dipeptide is determined by the $pK_a$ values of the side chains of its constituent amino acids.

Step 2: Meaning
Basic amino acids include Lysine (Lys), Arginine (Arg), and Histidine (His). Among these, Arginine has the highest $pK_a$ (approximately 12.5).

Step 3: Analysis
Glycine (Gly) is neutral. Glutamic acid (Glu) is acidic. Between Lys, Arg, and His, Arginine's guanidino group is the most basic functional group.

Step 4: Conclusion
Gly-Arg is the most basic dipeptide because Arginine is the most basic amino acid. Final Answer: (C)