Table 2 The amino acids and the terminal groups that influence the pI of a protein with their charge polarity are shown. Four pKr values are tabulated for each of them, as defined by Lehninger [21], Solomon [22], Sillero [22], Rodwell [22]. In this work, Lehninger's values were used.
From: A Perl procedure for protein identification by Peptide Mass Fingerprinting
Amino acid | Polarity | pKr Lehninger | pKr Solomon | pKr Sillero | pKr Rodwell |
|---|---|---|---|---|---|
Glutamic acid (E) | - | 4.25 | 4.30 | 4.50 | 4.25 |
Aspartic acid (D) | - | 3.65 | 3.90 | 4.00 | 3.68 |
Cysteine (C) | - | 8.18 | 8.30 | 9.00 | 8.33 |
Tyrosine (Y) | - | 10.07 | 10.10 | 10.00 | 10.07 |
Histidine (H) | + | 6.00 | 6.00 | 6.40 | 6.00 |
Lysine (K) | + | 10.53 | 10.50 | 10.40 | 11.50 |
Arginine (R) | + | 12.48 | 12.50 | 12.00 | 11.50 |
Carboxyl terminal (COOH) | - | 3.10 | 2.40 | 3.20 | 3.10 |
Amino terminal (NH2) | + | 8.00 | 9.60 | 8.20 | 8.00 |