ExPASy - Protein Identification Tools

Mass differences due to amino acid substitutions (average 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 monoisotopic mass values for the amino acid masses.

ACDEFGHIKLMNPQRSTVWY
A- 32.06 44.01 58.04 76.10 -14.03 66.06 42.08 57.10 42.08 60.11 43.03 26.04 57.05 85.11 16.00 30.03 28.05 115.13 92.10A
C -32.06- 11.95 25.98 44.04 -46.09 34.00 10.02 25.04 10.02 28.05 10.97 -6.02 24.99 53.05 -16.06 -2.03 -4.01 83.07 60.04C
D -44.01 -11.95- 14.03 32.09 -58.04 22.05 -1.93 13.09 -1.93 16.10 -0.98 -17.97 13.04 41.10 -28.01 -13.98 -15.96 71.12 48.09D
E -58.04 -25.98 -14.03- 18.06 -72.06 8.03 -15.96 -0.94 -15.96 2.08 -15.01 -32.00 -0.98 27.07 -42.04 -28.01 -29.98 57.10 34.06E
F -76.10 -44.04 -32.09 -18.06- -90.12 -10.04 -34.02 -19.00 -34.02 -15.98 -33.07 -50.06 -19.05 9.01 -60.10 -46.07 -48.04 39.04 16.00F
G 14.03 46.09 58.04 72.06 90.12- 80.09 56.11 71.12 56.11 74.14 57.05 40.06 71.08 99.14 30.03 44.05 42.08 129.16 106.12G
H -66.06 -34.00 -22.05 -8.03 10.04 -80.09- -23.98 -8.97 -23.98 -5.95 -23.04 -40.02 -9.01 19.05 -50.06 -36.04 -38.01 49.07 26.03H
I -42.08 -10.02 1.93 15.96 34.02 -56.11 23.98- 15.01 0.00 18.03 0.94 -16.04 14.97 43.03 -26.08 -12.05 -14.03 73.05 50.02I
K -57.10 -25.04 -13.09 0.94 19.00 -71.12 8.97 -15.01- -15.01 3.02 -14.07 -31.06 -0.04 28.01 -41.10 -27.07 -29.04 58.04 35.00K
L -42.08 -10.02 1.93 15.96 34.02 -56.11 23.98 0.00 15.01- 18.03 0.94 -16.04 14.97 43.03 -26.08 -12.05 -14.03 73.05 50.02L
M -60.11 -28.05 -16.10 -2.08 15.98 -74.14 5.95 -18.03 -3.02 -18.03- -17.09 -34.08 -3.06 24.99 -44.11 -30.09 -32.06 55.02 31.98M
N -43.03 -10.97 0.98 15.01 33.07 -57.05 23.04 -0.94 14.07 -0.94 17.09- -16.99 14.03 42.08 -27.03 -13.00 -14.97 72.11 49.07N
P -26.04 6.02 17.97 32.00 50.06 -40.06 40.02 16.04 31.06 16.04 34.08 16.99- 31.01 59.07 -10.04 3.99 2.02 89.10 66.06P
Q -57.05 -24.99 -13.04 0.98 19.05 -71.08 9.01 -14.97 0.04 -14.97 3.06 -14.03 -31.01- 28.06 -41.05 -27.03 -29.00 58.08 35.05Q
R -85.11 -53.05 -41.10 -27.07 -9.01 -99.14 -19.05 -43.03 -28.01 -43.03 -24.99 -42.08 -59.07 -28.06- -69.11 -55.08 -57.05 30.03 6.99R
S -16.00 16.06 28.01 42.04 60.10 -30.03 50.06 26.08 41.10 26.08 44.11 27.03 10.04 41.05 69.11- 14.03 12.05 99.14 76.10S
T -30.03 2.03 13.98 28.01 46.07 -44.05 36.04 12.05 27.07 12.05 30.09 13.00 -3.99 27.03 55.08 -14.03- -1.97 85.11 62.07T
V -28.05 4.01 15.96 29.98 48.04 -42.08 38.01 14.03 29.04 14.03 32.06 14.97 -2.02 29.00 57.05 -12.05 1.97- 87.08 64.04V
W -115.13 -83.07 -71.12 -57.10 -39.04 -129.16 -49.07 -73.05 -58.04 -73.05 -55.02 -72.11 -89.10 -58.08 -30.03 -99.14 -85.11 -87.08- -23.04W
Y -92.10 -60.04 -48.09 -34.06 -16.00 -106.12 -26.03 -50.02 -35.00 -50.02 -31.98 -49.07 -66.06 -35.05 -6.99 -76.10 -62.07 -64.04 23.04-Y