Complete properties for all 20 standard amino acids found in proteins.
| Name | 3-Letter | 1-Letter | MW (Da) | pKa (side) | Hydropathy | Category | Essential |
|---|---|---|---|---|---|---|---|
| Alanine | Ala | A | 89.09 | — | 1.8 | Nonpolar | No |
| Arginine | Arg | R | 174.20 | 12.48 | -4.5 | Positive | Semi |
| Asparagine | Asn | N | 132.12 | — | -3.5 | Polar | No |
| Aspartate | Asp | D | 133.10 | 3.65 | -3.5 | Negative | No |
| Cysteine | Cys | C | 121.16 | 8.18 | 2.5 | Special | Semi |
| Glutamate | Glu | E | 147.13 | 4.25 | -3.5 | Negative | No |
| Glutamine | Gln | Q | 146.15 | — | -3.5 | Polar | No |
| Glycine | Gly | G | 75.03 | — | -0.4 | Special | No |
| Histidine | His | H | 155.16 | 6.00 | -3.2 | Positive | Yes |
| Isoleucine | Ile | I | 131.17 | — | 4.5 | Nonpolar | Yes |
| Leucine | Leu | L | 131.17 | — | 3.8 | Nonpolar | Yes |
| Lysine | Lys | K | 146.19 | 10.53 | -3.9 | Positive | Yes |
| Methionine | Met | M | 149.21 | — | 1.9 | Nonpolar | Yes |
| Phenylalanine | Phe | F | 165.19 | — | 2.8 | Nonpolar | Yes |
| Proline | Pro | P | 115.13 | — | -1.6 | Special | No |
| Serine | Ser | S | 105.09 | — | -0.8 | Polar | No |
| Threonine | Thr | T | 119.12 | — | -0.7 | Polar | Yes |
| Tryptophan | Trp | W | 204.23 | — | -0.9 | Nonpolar | Yes |
| Tyrosine | Tyr | Y | 181.19 | 10.07 | -1.3 | Polar | Semi |
| Valine | Val | V | 117.15 | — | 4.2 | Nonpolar | Yes |
MW (Da) is the molecular weight of the amino acid residue in Daltons. pKa (side) is the dissociation constant of the side chain — only charged or ionizable residues have this. Hydropathy uses the Kyte-Doolittle scale: positive values are hydrophobic (prefer the protein interior), negative values are hydrophilic (prefer the surface).
Essential amino acids cannot be synthesized by the human body and must come from diet. There are 9 essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Arginine, cysteine, and tyrosine are semi-essential (needed during growth or illness).
Use the Sequence Analyzer to calculate amino acid composition for any protein, or the Structure Predictor to visualize protein structures colored by residue type.