ExPASy - Protein Identification Tools

Mass differences due to amino acid substitutions (monoisotopic mass values):

Example:
To look up the mass difference caused by "E->Q" (a Glutamic acid is replaced by a Glutamine), go to the line of the table labeled "E" and follow this line until you get to the column labeled "Q": -0.98. The substitution "E->Q" decreases the mass of your peptide by 0.98.

You may also access the corresponding table based on average mass values for the amino acid masses.

ACDEFGHIKLMNPQRSTVWY
A- 31.97 43.99 58.01 76.03 -14.02 66.02 42.05 57.06 42.05 60.00 43.01 26.02 57.02 85.06 15.99 30.01 28.03 115.04 92.03A
C -31.97- 12.02 26.03 44.06 -45.99 34.05 10.07 25.09 10.07 28.03 11.03 -5.96 25.05 53.09 -15.98 -1.96 -3.94 83.07 60.05C
D -43.99 -12.02- 14.02 32.04 -58.01 22.03 -1.94 13.07 -1.94 16.01 -0.98 -17.97 13.03 41.07 -27.99 -13.98 -15.96 71.05 48.04D
E -58.01 -26.03 -14.02- 18.03 -72.02 8.02 -15.96 -0.95 -15.96 2.00 -15.00 -31.99 -0.98 27.06 -42.01 -27.99 -29.97 57.04 34.02E
F -76.03 -44.06 -32.04 -18.03- -90.05 -10.01 -33.98 -18.97 -33.98 -16.03 -33.03 -50.02 -19.01 9.03 -60.04 -46.02 -48.00 39.01 15.99F
G 14.02 45.99 58.01 72.02 90.05- 80.04 56.06 71.07 56.06 74.02 57.02 40.03 71.04 99.08 30.01 44.03 42.05 129.06 106.04G
H -66.02 -34.05 -22.03 -8.02 10.01 -80.04- -23.97 -8.96 -23.97 -6.02 -23.02 -40.01 -9.00 19.04 -50.03 -36.01 -37.99 49.02 26.00H
I -42.05 -10.07 1.94 15.96 33.98 -56.06 23.97- 15.01 0.00 17.96 0.96 -16.03 14.97 43.02 -26.05 -12.04 -14.02 73.00 49.98I
K -57.06 -25.09 -13.07 0.95 18.97 -71.07 8.96 -15.01- -15.01 2.95 -14.05 -31.04 -0.04 28.01 -41.06 -27.05 -29.03 57.98 34.97K
L -42.05 -10.07 1.94 15.96 33.98 -56.06 23.97 0.00 15.01- 17.96 0.96 -16.03 14.97 43.02 -26.05 -12.04 -14.02 73.00 49.98L
M -60.00 -28.03 -16.01 -2.00 16.03 -74.02 6.02 -17.96 -2.95 -17.96- -17.00 -33.99 -2.98 25.06 -44.01 -29.99 -31.97 55.04 32.02M
N -43.01 -11.03 0.98 15.00 33.03 -57.02 23.02 -0.96 14.05 -0.96 17.00- -16.99 14.02 42.06 -27.01 -13.00 -14.97 72.04 49.02N
P -26.02 5.96 17.97 31.99 50.02 -40.03 40.01 16.03 31.04 16.03 33.99 16.99- 31.01 59.05 -10.02 3.99 2.02 89.03 66.01P
Q -57.02 -25.05 -13.03 0.98 19.01 -71.04 9.00 -14.97 0.04 -14.97 2.98 -14.02 -31.01- 28.04 -41.03 -27.01 -28.99 58.02 35.00Q
R -85.06 -53.09 -41.07 -27.06 -9.03 -99.08 -19.04 -43.02 -28.01 -43.02 -25.06 -42.06 -59.05 -28.04- -69.07 -55.05 -57.03 29.98 6.96R
S -15.99 15.98 27.99 42.01 60.04 -30.01 50.03 26.05 41.06 26.05 44.01 27.01 10.02 41.03 69.07- 14.02 12.04 99.05 76.03S
T -30.01 1.96 13.98 27.99 46.02 -44.03 36.01 12.04 27.05 12.04 29.99 13.00 -3.99 27.01 55.05 -14.02- -1.98 85.03 62.02T
V -28.03 3.94 15.96 29.97 48.00 -42.05 37.99 14.02 29.03 14.02 31.97 14.97 -2.02 28.99 57.03 -12.04 1.98- 87.01 63.99V
W -115.04 -83.07 -71.05 -57.04 -39.01 -129.06 -49.02 -73.00 -57.98 -73.00 -55.04 -72.04 -89.03 -58.02 -29.98 -99.05 -85.03 -87.01- -23.02W
Y -92.03 -60.05 -48.04 -34.02 -15.99 -106.04 -26.00 -49.98 -34.97 -49.98 -32.02 -49.02 -66.01 -35.00 -6.96 -76.03 -62.02 -63.99 23.02-Y