Enhanced MALDI-TOF MS Analysis of Phosphopeptides Using an Optimized DHAP/DAHC Matrix
Table 1
The peptides investigated in this study.
Peptide ID
Sequence No.
Sequence
B+B
T1
aa 106–119
VPQLEIVPNpSAEER
1660.79
260
T2
aa 104 –119
KYKVPQLEIVPNpSAEER
1951.95
710
T3
aa 43–58
DIGpSEpSTEDQAMEDIK
1927.68
3960
T4
aa 59–79
QMEAEpSIpSpSpSEEIVPNpSVEQK
2720.90
3680
T5
aa 37–58
VNELpSKDIGpSEpSTEDQAMEDIK
2678.02
3840
T6
aa 138–149
TVDMEpSTEVFTK
1466.60
210
T7
aa 46–70
NANEEEYSIGpSpSpSEEpSAEVATEEVK
3008.02
7100
T8
aa 1–21
KNTMEHVpSpSpSEESIIpSQETYK
2747.00
2810
T9
aa 2–21
NTMEHVpSpSpSEESIIpSQETYK
2618.91
2350
T1
aa 33 –48
FQpSEEQQQTEDELQDK
2061.82
6200
T2
aa 1–25
RELEELNVPGEIVEpSLpSpSpSEESITR
3122.26
220
T10
aa 81–91
ALNEINQFYQK
1367.70
750
T4
aa 23–34
FFVAPFPEVFGK
1384.73
5530
T3
aa 8–22
HQGLPQEVLNENLLR
1759.59
590
T11
aa 91–100
YLGYLEQLLR
1267.71
6480
T18
aa 132–150
EPMIGVNQELAYFYPELFR
2316.14
6900
pT
—
VNQIGpTLSESIK
1368.44
310
pY
—
SGSLHRIpYTHQS
1465.48
2300
Phosphopeptides in tryptic digest of casein and casein are denoted as T1~2 and T1~9, respectively. The sites of phosphorylation are indicated with the letter “p” in the listed peptide sequences. T3, T4, T11, and T18 are nonphosphorylated peptide from casein S1. T10 is a nonphosphorylated peptide from -casein S2. pT and pY are the synthesized standard phosphopeptides. [M+H] denotes the theoretical monoisotopic m/z mass. “B+B” means Bull and Breese Index for peptides calculated by the Masslynx software (Waters/Micromass).