Question

Question A.

Phenylalanine (Phe) has highly negative value of z1-scale and positive value of z2-scale. Which of the five statements is/are correct?

a) Phe has negative charge at pH<7 and positive charge at pH>7 b) Phe is present in very few proteins c) Phe is a hydrophobic and bulky amino acid d) Phe has a large aromatic side chain e) Phe is a big and hydrophilic amino acid

B. Z-scale descriptors are also calculated for artificial (synthetic) amino acids.

Which of the four following descriptions could correspond to vinylglycine and which to homoarginine? Motivate your answer!

1) z1=3.81 z2=1.17 z3=3.54

2) z1=2.70 z2=-3.06 z3=-4.15

3) z1=-0.81 z2=1.17 z3=3.54

4) z1=2.70 z2=3.06 z3=-4.15

Answer 1

A.e) Phe is a big and hydrophilic amino acid. z1 for 'hydrophobicity', z2 for 'bulk of side-chain' So since z1 is negative, it denotes that it is hydrophilic(less hydrophobic) and since z2 is positive, it denotes its very bulky an big

B.vinylglycine 4) z1=2.70 z2=3.06 z3=-4.15 Since glycine originally has z1 =2.19, the addition of the vinyl group increased the hydrophobic character. The z2 of glycine is 0.53 and the addition of vinyl would make it bulkier. So I chose this answer