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.

	A	C	D	E	F	G	H	I	K	L	M	N	P	Q	R	S	T	V	W	Y
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	92.03	A
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	60.05	C
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	48.04	D
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	34.02	E
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	15.99	F
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	106.04	G
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	26.00	H
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	49.98	I
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	34.97	K
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	49.98	L
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	32.02	M
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	49.02	N
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	66.01	P
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	35.00	Q
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	6.96	R
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	76.03	S
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	62.02	T
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	63.99	V
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	-	-23.02	W
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

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