Table 2.
Inductive index (ii) values calculated for each side-chain on the Cα of all 15 non-aromatic α-amino acids and experimentally determined pKa values of their α-NH3+ groups (ranked from highest to lowest). The pKa values of non-ionizable α-amino groups are the same as in Table 1 and are included for comparison. The state of ionizable side-chain groups (used for calculations) are indicated in parentheses.
| Side chain |
ii of side-chain on Cα (x 103) |
α-NH3+ pKa |
|---|---|---|
| Cys (thiol ionized) | −339.6 | 10.33 ± 0.02 |
| Asp (β-carboxyl ionized) | −162.5 | 9.76 ± 0.02 |
| Ala | −134.0 | 9.80 ± 0.02 |
| Val | −127.1 | 9.55 ± 0.01 |
| Ile | −96.8 | 9.69 ± 0.01 |
| Glu (γ-carboxyl ionized) | −91.3 | 9.74 ± 0.01 |
| Leu | −72.8 | 9.64 ± 0.01 |
| Gly | −53.2 | 9.68 ± 0.01 |
| Met | 19.7 | 9.15 ± 0.02 |
| Arg (guanidinium ionized) | 46.5 | 9.08 ± 0.01 |
| Lys (ε-amino ionized) | 62.8 | 9.16 ± 0.01 |
| Ser | 81.5 | 9.11 ± 0.02 |
| Gln | 89.3 | 9.15 ± 0.01 |
| Thr | 92.3 | 9.01 ± 0.01 |
| Asn | 180.8 | 8.80 ± 0.02 |