Table I

List of phosphorylated peptides identified from the standard peptide mixture using MALDI MS

The detected phosphorylated peptides from the standard protein digest were calculated by General Protein/Mass Analysis for Windows (GPMAW) 6.0. The phosphorylated peptides were derived by tryptic digestion of ovalbumin (Ov.), α-casein S1 (α-S1.) and S2 (α-S2.), and β-casein (β-C.). The phosphorylation sites are bold and underlined.

Peptide sequenceNo. of phosphate groups(M + H)+
Da
EQLSTSEENSK (α-S2. 141–151)21411.50
TVDMESTEVFTK (α-S2. 153–164)11466.61
TVDMESTEVFTKK (α-S2. 153–165)11594.70
VPQLEIVPNSAEER (α-S1. 121–134)11660.79
DIGSESTEDQAMEDIK (α-S1. 58–73)21927.69
YKVPQLEIVPNSAEER (α-S1. 119–134)11951.95
FQSEEQQQTEDELQDK (β-C. 33–48)12061.83
EVVGSAEAGVDAASVSEEFR (Ov. 340–359)12088.89
NVPGEIVESLSSSEESITR (β-C. 22–40)42352.87
IEKFQSEEQQQTEDELQDK (β-C. 30–48)12432.10
LPGFGDSIEAQCGTSVNVHSSLR (Ov. 62–84)12511.13
FQSEEQQQTEDELQDKIHPF (β-C. 33–52)a12556.20
VNELSKDIGSESTEDQAMEDIK (α-S1. 52–73)32678.01
QMEAESISSSEEIVPNSVEQK (α-S1. 74–94)b52703.10
QMEAESISSSEEIVPNSVEQK (α-S1. 74–94)52720.91
KNTMEHVSSSEESIISQETYK (α-S2. 16–36)42745.99
EKVNELSKDIGSESTEDQAMEDIK (α-S1. 52–73)32935.15
NANEEEYSIGSSSEESAEVATEEVK (α-S2. 61–85)43008.01
RELEELNVPGEIVESLSSSEESITR (β-C. 16–40)43122.27
  • a Chymotryptic cleavage (sequence was verified by MALDI tandem MS).

  • b Variant of the sequence QMEAESISSSEEIVPNSVEQK (verified by MALDI MSMS).