Table II. Amino acid three and single letter codes, plus amino acid residue masses and elemental composition. Residue mass is defined as the amino acid minus water (i.e., NH-CHR-CO).
| Residue | 3/1 letter code | Composition | Mono. mass | Avg. mass |
|---|---|---|---|---|
| Alanine | Ala/A | C3N5NO | 71.03712 | 71.08 |
| Arginine | Arg/R | C6H12N4O | 156.10112 | 156.19 |
| Asparagine | Asn/N | C4H6N2O2 | 114.04293 | 114.10 |
| Aspartic acid | Asp/D | C4H5NO3 | 115.02695 | 115.09 |
| Cysteine | Cys/C | C3H5NOS | 103.00919 | 103.14 |
| Cysteine-cma | Cys/C | C5H8N2O2S | 160.03065 | 160.20 |
| Glutamine | Gln/Q | C5H8N2O2 | 128.05858 | 128.13 |
| Glutamic acid | Glu/E | C5H7NO3 | 129.04260 | 129.12 |
| Glycine | Gly/G | C2H3NO | 57.02147 | 57.05 |
| Histidine | His/H | C6H7N3O | 137.05891 | 137.14 |
| Isoleucine | Ile/I | C6H11NO | 113.08407 | 113.16 |
| Leucine | Leu/L | C6H11NO | 113.08407 | 113.16 |
| Lysine | Lys/K | C6H12N2O | 128.09496 | 128.17 |
| Methionine | Met/M | C5H9OS | 131.04049 | 131.19 |
| Methionine-oxb | Met/M | C5H9O2S | 147.03540 | 147.18 |
| Phenylalanine | Phe/F | C9H9NO | 147.06842 | 147.18 |
| Proline | Pro/P | C5H7NO | 97.05277 | 97.12 |
| Serine | Ser/S | C3H5NO2 | 87.03203 | 87.08 |
| Threonine | Thr/T | C4H7NO2 | 101.04768 | 101.10 |
| Tryptophan | Trp/W | C11H10N2O | 186.07932 | 186.21 |
| Tyrosine | Tyr/Y | C9H9NO2 | 163.06333 | 163.18 |
| Valine | Val/V | C5H9NO | 99.06842 | 99.13 |
a Carbamidomethylated cysteine.
b Oxidized methionine.