Quiz 2 Key
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The amino acid residues in the peptide below have these pKa's:

residue

1

2

3

4

α-COOH

1.83

2.02

2.32

2.17

α-NH3+

9.13

8.80

9.62

9.04

side chain

none

none

none

12.48


1-8. Identify the residues by writing their 3-letter and 1-letter abbreviations.

residue

1

2

3

4

3-letter abbreviation

Phe
Asn
Val
Arg

1-letter abbreviation

F
N
V
R

9-10. At what pH range (2 numbers) is the peptide shown?              9.13 - 12.48                

The amino acid residues in the peptide below have these pKa's:

residue

1

2

3

4

α-COOH

2.17

2.36

1.82

2.38

α-NH3++

9.13

9.60

9.17

9.39

side chain

none

none

6.00

none


1-8. Identify the residues by writing their 3-letter and 1-letter abbreviations.

residue

1

2

3

4

3-letter abbreviation

Gln
Leu
His
Trp

1-letter abbreviation

Q
L
H
W

9-10. At what pH range (2 numbers) is the peptide shown?          6.00 - 9.13                  

The amino acid residues in the peptide below have these pKa's:

residue

1

2

3

4

α-COOH

2.36

1.88

2.20

2.11

α-NH3++

9.68

9.60

9.11

9.62

side chain

none

3.65

10.07

none


1-8. Identify the residues by writing their 3-letter and 1-letter abbreviations.

residue

1

2

3

4

3-letter abbreviation

Ile
Asp
Tyr
Thr

1-letter abbreviation

I
D
Y
T

9-10. At what pH range (2 numbers) is the peptide shown?            3.65 - 9.68                  

The amino acid residues in the peptide below have these pKa's:

residue

1

2

3

4

α-COOH

2.21

1.99

2.19

2.18

α-NH3+

9.15

10.96

9.67

8.95

side chain

none

none

4.25

10.53


1-8. Identify the residues by writing their 3-letter and 1-letter abbreviations.

residue

1

2

3

4

3-letter abbreviation

Ala
Pro
Glu
Lys

1-letter abbreviation

A
P
E
K

9-10. At what pH range (2 numbers) is the peptide shown?      2.18 - 4.25        

Comments on grading: If you misidentified the amino acid (said alanine was glycine, for example) and then had a one-letter abbreviation that agreed (G, not A), you lost 1 point for the original identification only.

It's pretty clear that the big problem is pH. I'll try to get the key for the amino acids and pH exercise posted late this afternoon.

 

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