Table 1.

Peptide sequences determined from MS/MS data

MH+	Sequence
961.4	[IL]a[IL]QESSER
808.4	YGA[IL]EQK
956.6	AE[IL]TNRPR
936.52	KYGA[IL]EQK
1041.48	{DF}bEF[IL]ENK
1370.63	FADC*S[IL][IL]YPER
1262.6	M(O)cAD[IL][IL]GANWQK
1246.58	MAD[IL][IL]GANWQK
1278.6	MAD[IL][IL]GANW(O2)cQK
2051.08	{DT/ESd}VY[IL][IL]G[QK]eE[IL]GGTDTVE[IL]K
1526.75	RFADC*S[IL][IL]YPER
1385.76	[IL]F[IL]NE[QK]VFTFK
1669.9	VAN[IL]F[IL]NE[QK] VFTFK

C* stands for carbamidomethyl Cys.

^aLow-energy CID analysis cannot differentiate between isomeric Ile and Leu residues.

^bThe order of the amino acids could not be determined.

^cOxidation of methionine and tryptophan are common side-reactions.

^dAmino acid combinations corresponding to the mass difference observed.

^eGln and Lys are isobaric amino acids with identical nominal masses, but different elemental composition. Since the QSTAR mass spectrometer affords a 50 ppm mass accuracy, in most cases these residues could be identified, however there are exceptions.