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. Author manuscript; available in PMC: 2010 Nov 16.
Published in final edited form as: J Am Soc Mass Spectrom. 2010 Jun 19;21(10):1649–1659. doi: 10.1016/j.jasms.2010.06.005

Figure 2.

Figure 2

MALDI mass spectra of an α- and β-casein tryptic digest resulting from A) titanium dioxide NuTip enrichment, B) zirconium dioxide NuTip enrichment, and C) a mixed resin tip enrichment consisting of zirconium and titanium dioxide. The ion labeled with an asterisk (*) corresponds in mass to a previously reported monophosphorylated casein variant (13). Ions labeled with filled circles represent non-specifically bound peptides.