Table 1. Polar Requirement (PR) of every proteinogenic amino acid as measured by Woese et al. (1966).
| Amino acid | Abbrev. | PR | Amino acid | Abbrev. | PR | Amino acid | Abbrev. | PR |
|---|---|---|---|---|---|---|---|---|
| Alanine | Ala | 7.0 | Glycine | Gly | 7.9 | Proline | Pro | 6.6 |
| Arginine | Arg | 9.1 | Histidine | His | 8.4 | Serine | Ser | 7.5 |
| Aspartic acid | Asp | 13.0 | Isoleucine | Ile | 4.9 | Threonine | Thr | 6.6 |
| Asparagine | Asn | 10.0 | Leucine | Leu | 4.9 | Tryptophan | Trp | 5.2 |
| Cysteine | Cys | 4.8 | Lysine | Lys | 10.1 | Tyrosine | Tyr | 5.4 |
| Glutamic acid | Glu | 12.5 | Methionine | Met | 5.3 | Valine | Val | 5.6 |
| Glutamine | Gln | 8.6 | Phenylalanine | Phe | 5.0 |