Determine the isoelectric pH (pl) of the amino acids (a) Met, M, (b) Glu, E and (c) Lys, K. Show your solutions clearly and systematically. Draw the structures (showing the states of protonation) of each amino acid before and after consecutive ionizations. Indicate the pH (i.e., pKa) values at which these ionizations occur. Specify the pKa values you used for the calculation of pl. The pKa values of the amino acids' ionizable groups are listed in the table below.

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1. Determine the isoelectric pH (pI) of the amino acids (a) Met, M, (b) Glu, E and (c) Lys,
K. Show your solutions clearly and systematically. Draw the structures (showing the
states of protonation) of each amino acid before and after consecutive ionizations.
Indicate the pH (i.e., pKa) values at which these ionizations occur. Specify the pKa
values you used for the calculation of pl. The pKa values of the amino acids' ionizable
groups are listed in the table below.
Table 23.2 The pK, Values of Amino Acids
pKa
a-COOH
pKa
a-NH3+
pKa
side chain
Amino acid
Alanine
2.34
9.69
Arginine
2.17
9.04
12.48
Asparagine
2.02
8.84
-
Aspartic acid
2.09
9.82
3.86
Cysteine
1.92
10.46
8.35
Glutamic acid
2.19
9.67
4.25
Glutamine
2.17
9.13
Glycine
2.34
9.60
Histidine
1.82
9.17
6.04
Isoleucine
2.36
9.68
Leucine
2.36
9.60
Lysine
2.18
8.95
10.79
Methionine
2.28
9.21
Phenylalanine
2.16
9.18
Proline
1.99
10.60
Serine
2.21
9.15
Threonine
2.63
9.10
Tryptophan
2.38
9.39
Tyrosine
2.20
9.11
10.07
Valine
2.32
9.62
|
Transcribed Image Text:1. Determine the isoelectric pH (pI) of the amino acids (a) Met, M, (b) Glu, E and (c) Lys, K. Show your solutions clearly and systematically. Draw the structures (showing the states of protonation) of each amino acid before and after consecutive ionizations. Indicate the pH (i.e., pKa) values at which these ionizations occur. Specify the pKa values you used for the calculation of pl. The pKa values of the amino acids' ionizable groups are listed in the table below. Table 23.2 The pK, Values of Amino Acids pKa a-COOH pKa a-NH3+ pKa side chain Amino acid Alanine 2.34 9.69 Arginine 2.17 9.04 12.48 Asparagine 2.02 8.84 - Aspartic acid 2.09 9.82 3.86 Cysteine 1.92 10.46 8.35 Glutamic acid 2.19 9.67 4.25 Glutamine 2.17 9.13 Glycine 2.34 9.60 Histidine 1.82 9.17 6.04 Isoleucine 2.36 9.68 Leucine 2.36 9.60 Lysine 2.18 8.95 10.79 Methionine 2.28 9.21 Phenylalanine 2.16 9.18 Proline 1.99 10.60 Serine 2.21 9.15 Threonine 2.63 9.10 Tryptophan 2.38 9.39 Tyrosine 2.20 9.11 10.07 Valine 2.32 9.62 |
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