6. Examine the following four amino acids (I, I,II,Iv) and answer the following

Question

6. Examine the following four amino acids (I, I,II,Iv) and answer the following questions a) (8 pts) What are the three-letter abbreviation codes for amino acids 1-HV? NH, b) (4 pts) Match each of the amino acids above (I, II, II, IV) with ONE characteristic below a) Hydrophobic side chain b) Basic side chain c) Disrupts the a-helix d) Modified form of phenylalanine c) (2 pts) Comparing amino acids IlI and IV, which one should have the lower solubility in water? Explain your answer. d) (6 pts) Draw the peptide with the amino acid sequence 1-1I-IV AND cirdle the N terminus and the C termin e) (4 pts) What is the net charge on the peptide at pH 7? Explain your reasoning (use the pK, table provided). Page 3 of 5

Explanation / Answer

a) (i)Pro, (ii)Tyr (iii)Leu (iv)Lys

b) (i)III (ii) IV (iii) I (iv)II

c) The III (Leu) has lower solubility in water.It is because it has non polar part (CH2CHMe2).This nonpolar part has the hydrophobic interaction with water.But the IV(Lys) has the basic part(CH2CH2CH2CH2NH2) which forms H-bonding with water.So III has lower solubility.

d) H2N-CH(CH2C6H4OH)-CO-NH-CH(CHMe2)-CO-NH-CH(CH2CH2CH2CH2NH2)-COOH

N-terminal C-terminal

e)

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