Here is the set of monoisotopic and average amino acid masses and elemental mass values used by the tools developed here. The amino acid masses are the sums of the elemental masses, and the elemental masses are from Unimod. You can also download this spreadsheet, which calculates the average and monoisotopic masses for each amino acid from the listed elemental values (which you can change). Please send me an email if you notice an error!
Note that these are residue masses as they appear in a peptide or protein. Add the N-terminus (H) and C-terminus (OH) groups to calculate the neutral mass of the peptide or protein.
Amino Acids
| Amino acid |
Code |
Abbreviation |
Composition |
Mono mass |
Avg mass |
| Glycine |
G |
GLY |
C2H3NO |
57.021463735 |
57.05132 |
| Alanine |
A |
ALA |
C3H5NO |
71.037113805 |
71.0779 |
| Serine |
S |
SER |
C3H5NO2 |
87.032028435 |
87.0773 |
| Proline |
P |
PRO |
C5H7NO |
97.052763875 |
97.11518 |
| Valine |
V |
VAL |
C5H9NO |
99.068413945 |
99.13106 |
| Threonine |
T |
THR |
C4H7NO2 |
101.047678505 |
101.10388 |
| Cysteine |
C |
CYS |
C3H5NOS |
103.009184505 |
103.1429 |
| Leucine |
L |
LEU |
C6H11NO |
113.084064015 |
113.15764 |
| Isoleucine |
I |
ILE |
C6H11NO |
113.084064015 |
113.15764 |
| Asparagine |
N |
ASN |
C4H6N2O2 |
114.042927470 |
114.10264 |
| Aspartic acid |
D |
ASP |
C4H5NO3 |
115.026943065 |
115.0874 |
| Glutamine |
Q |
GLN |
C5H8N2O2 |
128.058577540 |
128.12922 |
| Lysine |
K |
LYS |
C6H12N2O |
128.094963050 |
128.17228 |
| Glutamic acid |
E |
GLU |
C5H7NO3 |
129.042593135 |
129.11398 |
| Methionine |
M |
MET |
C5H9NOS |
131.040484645 |
131.19606 |
| Histidine |
H |
HIS |
C6H7N3O |
137.058911875 |
137.13928 |
| Phenylalanine |
F |
PHE |
C9H9NO |
147.068413945 |
147.17386 |
| Selenocysteine |
U |
SEC |
C3H5NOSe |
150.953633405 |
150.3079 |
| Arginine |
R |
ARG |
C6H12N4O |
156.101111050 |
156.18568 |
| Tyrosine |
Y |
TYR |
C9H9NO2 |
163.063328575 |
163.17326 |
| Tryptophan |
W |
TRP |
C11H10N2O |
186.079312980 |
186.2099 |
| Pyrrolysine |
O |
PYL |
C12H19N3O2 |
237.147726925 |
237.29816 |
Atomic Elements
| Element |
Symbol |
Mono mass |
Avg mass |
| Hydrogen |
H |
1.007825035 |
1.00794 |
| Carbon |
C |
12.0000000 |
12.0107 |
| Nitrogen |
N |
14.003074 |
14.0067 |
| Oxygen |
O |
15.99491463 |
15.9994 |
| Phosphorus |
P |
30.973762 |
30.973761 |
| Sulfur |
S |
31.9720707 |
32.065 |
| Selenium |
Se |
79.9165196 |
79.96 |
| Proton |
|
1.00727646688 |
1.00739 |
Common Modifications
| Modification |
Residues |
Composition |
Mono mass |
Avg mass |
| Phosphorylation |
STY |
HPO3 |
79.966331 |
79.9799 |
| Oxidation |
M |
O |
15.994915 |
15.9994 |
| Acetylation |
K |
C2H2O |
42.010565 |
42.0367 |
| Carbamidomethyl |
C |
C2H3NO |
57.021464 |
57.0513 |