9780521516358book.pdf

1368.45(M

+Na)

+

1370.46

1249.55

1248.53

1271.61

1390.44

1244.54

1272.60

1392.45

1155.53

1398.52

1225.59

1146.60

1067.62

1441.44

1513.72 1056.35

928.30

956.33

.15

862.33

749.13

1026.20

1230.45(-H

O) 2

1056.36

616.20

713.24

684.11

910.12

1249.72MH

+, -H, -H

PO 3

4

y^8

843.23

b^6

-NH

3

b^3

405.95

y^9

956.36

y^7

730.18

y^5

547.10

b^8

-H

O 2

b^6

-H

O 2

b^8

928.23

b^9

-NH

3

1039.28

b^7

799.28

b^10

-H

O 2

1109.38

b^9

(M

+H)

+

1346.48

1347.49(M

+H)

+,

13

C

1248.45

b^10

1127.3810

m/z

1000 1050 1100 1150 1200 1250 1300 1350

1400 1450 1500

800

700

900 1000 1100 1200 1300

m

/z

400

0

500

600

700

800

900

1000

1100

1200

m

/z

MS

2

MS

3

Fig. 9.25

MS identification of phosphopeptides. Sequence is YEILNS

PEKAC where S

Pis phosphoserine. The MS

2 and MS

3 spectra are shown. The first tandem MS experiment

mainly results in loss of H

PO 3

, 98 Da. Particular problems may also be associated with electrospray mass spectrometry of phosphopeptides, where a high level of Na 4

þ

and

Kþ

adducts is regularly seen.