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. Author manuscript; available in PMC: 2010 Dec 1.
Published in final edited form as: J Proteome Res. 2009 Dec;8(12):5523–5531. doi: 10.1021/pr900603n

Table 1.

Summary of serum phosphopeptide identification by LTQ-Orbitrap a

Total matched
spectra		 Total non-
phosphopeptide
spectra (% total)		 Total
phosphopeptide
spectra (% total)		 Total unique
phosphopeptides
One round
TiO2 enrichment		 526 178 (33.8%) 348 (66.2%) 48
Two rounds
TiO2 enrichment		 275 16 (5.8%) 259 (94.2%) 60
Albumin/IgG
depletion fraction		 357 86 (24.1%) 271 (75.9%) 23
Albumin/IgG
bound fraction		 320 238 (74.4%) 82 (25.6%) 27
Cell lysate 486 62 (12.8%) 424 (87.2%) 228
a

All results were obtained using the following criteria to filter the SEQUEST search results: “ranked top #1; Xcorr versus charge 1.8, 2.5 for 2+, 3+ ions; mass accuracy 3 ppm; probability of randomized identification of peptide < 0.05”. The estimated false discovery rate by searching combined forward and reversed database is lower than 1%.