REACTIVE SPECIES - Oxidation of Amino Acids, Peptides, and Proteins: Kinetics and Mechanism - page 16

TABLE 1.5. Number of Oxidations Detected by LC/FT-MS and Reactive Amino
Acid Residues Identified by LC/MS/MS for Apomyoglobin

Site of
Oxidation
Detected by
LC/MS/MS a

Solvent-
Accessible
Surface Area by
NMR (A 2 )

Measure Mass
(Da) by LC/
FT-MS a

Oxidation
Detected by LC/
FT-MS a

Peptide
Residues

1-16 1830.8891 M + O S3 58.7

E6 47.5

W7 19.0

Q8 83.7

L11 42.6

K16 47.8

17-31 1637.8371 M + 1O Q26 19.3

1653.8321 M + 2O E27 54.1

32-42 1286.6506 M + 1O

1302.6455

M + 2O

43-47 699.3591 M + O

51-62 1366.6286 M + O M55 7.3

64-77 1521.9242 M + 1O H64 33.0

1537.9191 M + 2O T66 35.7

88-98 1248.6620 M + 2O P88 61.6

L89 48.6

S92 23.9

H93 58.5

H96 55.9

119-133 1517.6568 M + 1O M131 0.2

1533.6517 T132 52.3

M + 2O

134-139 763.4228 M + O

140-145 646.3286 M + O

148-153 665.3020 M + O

a Eleven peptides are detected as oxidized peptides in LC/FT-MS analysis, although six oxidized
peptides are observed in LC/MS/MS. The solvent-accessible surface areas were calculated using
GETAREA 1.1 [337] using NMR structure of horse heart myoglobin [339].
Adapted from Aye et al. [141] with the permission of the American Chemical Society.

[157]. Loss of H 2 O, CO, and ammonia from the sequence fragmented ions
can usually be observed by comparing the two high- and low-energy CID
spectra [154]. The fragmentation efficiency of the chemical modification of a
peptide can significantly improve in low-energy CID. A protonated basic
amino acid residue or positively charged derivative located at the N-terminus
of a peptide promotes the fragmentation of b-ion fragments (see Fig. 1.6).
Quaternary ammonium and phosphonium groups have been shown to enhance
fragmentation [171, 172]. The sulfonation of peptides by reagents such as
chlorosulfonylacetyl chloride, sulfobenzoic acid cyclic anhydride, 4-sulfophenyl
isothiocyanate, and 3-sulfopropionic acid N -hydroxysuccinimide ester display