Structural changes of Amino Acids according pH values
Structural changes of Amino Acids according pH value
Hello friends , welcome back to my blog … today I will
discuss about how you can easily determine the structural changes along different
pH value . Lets make it easy….
Amino acid |
pKa1 |
pKa2 |
pKa3 |
pI |
Glycine |
2.34 |
9.60 |
--- |
5.97 |
Alanine |
2.34 |
9.69 |
--- |
6.00 |
Valine |
2.32 |
9.62 |
--- |
5.96 |
Leucine |
2.36 |
9.60 |
--- |
5.98 |
Isoleucine |
2.36 |
9.60 |
--- |
6.02 |
Methionine |
2.28 |
9.21 |
--- |
5.74 |
Proline |
1.99 |
10.60 |
--- |
6.30 |
Phenylalanine |
1.83 |
9.13 |
--- |
5.48 |
Tryptophan |
2.83 |
9.39 |
--- |
5.89 |
Asparagine |
2.02 |
8.80 |
--- |
5.41 |
Glutamine |
2.17 |
9.13 |
--- |
5.65 |
Serine |
2.21 |
9.15 |
--- |
5.68 |
Threonine |
2.09 |
9.10 |
--- |
5.60 |
Tyrosine |
2.20 |
9.11 |
--- |
5.66 |
Cysteine |
1.96 |
8.18 |
--- |
5.07 |
Aspartic acid |
1.88 |
9.60 |
3.65 |
2.77 |
Glutamic acid |
2.19 |
9.67 |
4.25 |
3.22 |
Lysine |
2.18 |
8.95 |
10.53 |
9.74 |
Arginine |
2.17 |
9.04 |
12.48 |
10.76 |
Histidine |
1.82 |
9.17 |
6.00 |
7.59 |
Table
of pKa and pI values
- The
pKa values and the isoelectronic point, pI, are given
below for the 20 α-amino acids.
- pKa1=
α-carboxyl group, pKa2 = α-ammonium ion, and pKa3 =
side chain group.
Lets discus about the rule for determining
the structure for amino acids
1.
if the pH < pka then protonation [as there
will more H+ present for protonation of amino acids because of less pH]
2.
if the pH > pka then deprotonation [ as the
pH is high then there will more OH- ready to grab H+ to make H2O]
lets
take an example ….lysine at pH =1,9 and 5
Nicely described
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