Ltq orbitrap xl discovery

NMR spectra were recorded on ARX-400 Advance spectrometer (Bruker Corporation). FTIR spectra were obtained on a Nicolet iS10 infrared spectrometer (Thermo Scientific, Madison, WI) in reflection geometry using a single bounce diamond attenuated total reflectance (ATR) accessory. LPA were separated on a Luna^™ C-8 (50 × 2 mm, 3 μm) column connected to a guard cartridge with 2.0 to 3.0 mm internal diameters (Phenomenex, Torrance, CA) in an Accela^™ UHPLC system (Thermo Scientific, Madison, WI). MS data were collected via an LTQ-Orbitrap^™ XL Discovery instrument (Thermo Scientific, Madison, WI), equipped with an ESI ion max source. All chemicals were purchased from Sigma-Aldrich (St. Louis, MO) and used without further purification except when specifically mentioned. All phospholipids were purchased from Avanti Polar Lipids (Alabaster, AL). Ethylene glycol dimethacrylate (EGDMA) was purified by vacuum distillation. Human plasma was collected by Lampire Biological Laboratories Inc., from female donors, processed to obtain platelet-free plasma, and frozen at −80 °C. Empty SPE tubes and frits were purchased from Sigma-Aldrich (St. Louis, MO). HPLC grade MeOH, CHCl₃ and water were purchased from Honeywell International Inc.

Peaks from RP-HPLC were analyzed in a LTQ Orbitrap XL Discovery equipped with a ESI source (Thermo Fisher Scientific) in positive ion mode. For the direct-infusion experiments, a flow of 15 μL/min was provided by a syringe pump using a 250 μL syringe (Hamilton, Reno, NV, USA). The following settings were applied: capillary voltage of −4.0 kV, mass range of m/z 125 to 2,000 and capillary temperature of 260 °C. Calibration was performed with standard calibration mixture containing caffeine (m/z 195), MRFA peptide (m/z 524) and Ultramark 1600 (m/z 1,022–1,922).