Analysis of Erythroleukemia

Samples were subjected to LC–MS analysis using a dual pressure LTQ-Orbitrap Elite mass spectrometer (Thermo Fisher Scientific) connected to an electrospray ion source (Thermo Fisher Scientific) as recently described (PMID: 23017020). Peptide separation was carried out on an EASY nLC-1000 system (Thermo Fisher Scientific) equipped with a RP-HPLC column (75 μm × 30 cm) packed in-house with C18 resin (ReproSil-Pur C18–AQ, 1.9 μm resin, Dr. Maisch GmbH). A step-wise gradient from 95% solvent A (0.1% formic acid) and 5% solvent B (80% acetonitrile, 0.1% formic acid) to 50% solvent B over 60 min at a flow rate of 0.2 μl/min was used. Data acquisition mode was set to obtain one high resolution MS scan in the FT part of the mass spectrometer at a resolution of 240,000 full width at half-maximum (at m/z 400) followed by 20 MS/MS scans (TOP20) in the linear ion trap of the most intense ions using rapid scan speed. Unassigned and singly charged ions were excluded from analysis. Dynamic exclusion duration was set to 30 seconds.