Ms320 mass spectrometer

The glycolipid AT-X was treated with 3 m HCl in CH₃OH (Supelco) overnight at 80 °C to both release the fatty acyl groups from AT-X and form their methyl esters. The sample was then dried and dissolved in 50 μl of N,O-bis(trimethylsilyl) trifluoroacetamide (Sigma-Aldrich) and heated at 60 °C for 10 min prior to injection for GC/MS to form the trimethylsilyl ethers of any hydroxyl groups. Samples were injected directly from the silylating reagent. Analyses were carried out using a CP 3800 gas chromatograph (Varian) equipped with an MS320 mass spectrometer in the electron impact mode and scanning from m/z 50 to 800 over 0.5 s. Helium was used as the carrier gas with a flow rate of 1 ml/min. The samples were run on a DB 5 column (10 m × 0.20-mm inner diameter). The injector (splitless mode) was set for 250 °C. The oven temperature was held at 50 °C for 1 min, programmed at 30 °C/min to 130 °C, and then programmed at 10 °C/min to 330 °C, followed by a 10-min hold. The data analyses were carried out on a Varian WS data station.

For the 1-(α/β-O- (R)-2-octyl)- 2,3,5 tri-O- trifluoroactyl-D-arabinofurano/ pyranoside analysis, the oven temperature was held at 50°C for 1 min and programmed at 20°C/min to 150°C and then programmed at 2.5°C/min to 200°C. For the TMS-derivatives of the D-arabinose and the uniformly labeled ¹³C₅- arabinose internal standard ions at m/z 204, 217 and 206, 220 respectively were monitored on a SIM scan program. The TFAA-derivatives were monitored by MS/MS using m/z 420.9 (parent ion) to 192.9 (daughter ion), and m/z 425.9 (parent ion) to 197.9 (daughter ion) respectively for D-arabinose and D-UL-¹³C₅- arabinose as internal standard. For the TBSA analysis, the oven temperature was held at 50°C for 1 min and programmed at 30°C/min to 150°C and then 10°C/min to 300°C. The mass spectrometer was set for a Select Ion Monitoring (SIM) program in Chemical Ionization (CI) mode whereby the characteristic free fatty acyl anion at m/z 293.7 was monitored. GC/MS analyses were carried out using a CP 3800 gas chromatograph (Varian) equipped with an MS320 mass spectrometer.