The glycoproteins enriched from Caucasian American serum sample were digested with trypsin, and the digest was separated on a capillary column (Thermo Hypurity, C18, 150 x 0.075 mm) using Ettan MDLC system from GE Healthcare. The separation gradient was similar to that described in Section 2.2, except that the starting point was 0% ACN due to the use of a trap column (Michrom Bio-resources, Auburn, CA, USA) in front of the separation column. The resolved peptides were analyzed on an LTQ mass spectrometer (Thermo Electron) with an ESI ion source. The temperature ofthe ion transfer tube was controlled at 185°C and the spray voltage was 2.0 kV. The normalized collision energy was set at 35% for MS/MS. Data-dependent ion selection was monitored to select the most abundant five ions from an MS scan for MS/MS analysis. Dynamic exclusion was continued for a duration of2 min.
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