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. Author manuscript; available in PMC: 2008 Oct 20.
Published in final edited form as: J Proteome Res. 2005;4(2):424–434. doi: 10.1021/pr049804u

Figure 4.

Figure 4

Mass spectra of peptide products from trypsin proteolysis of Aec-modified bovine α-S1 casein digest (1 nmol) and synthetic phosphopeptide α-S1 casein 106–119 (6 nmol). (A.) (M+3H)3+ ion of Aec-modified phosphopeptide 106–119 (VPQLEIVPNAecAEER; label P) identified in Aec-modified α-S1 casein digest. (B.) (M+2H)2+ ion of expected product α-S1 casein 106–115 (VPQLEIVPNAec; label A), and (C.) (M+2H)2+ ion of product α-S1 casein 106–114 (VPQLEIVPN; label B) following trypsin proteolysis of Aec-modified α-S1 casein digest. (D.) (M+3H)3+ ion of Aec-modified synthetic phosphopeptide 106–119 substrate (label P). (E.) (M+2H)2+ ion of expected product α-S1 casein 106–115 (VPQLEIVPNAec; label A), and (F.) (M+2H)2+ ion of product α-S1 casein 106–114 (VPQLEIVPN; label B) after trypsin proteolysis of synthetic phosphopeptide α-S1 106–119.