VIBRATIONALLY COOLED MALDI, TLC MALDI FTMS FOR GANGLIOSIDES, NEUTRAL GLYCOLIPIDS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Our previously developed method of direct coupling of thin layer chromatography (TLC) with Vibrationally-Cooled (VC) MALDI-FTMS allows simple handling of TLC with FT high resolution which is not affected by the irregular surface of the TLC plate. Use of vibrational cooling is necessary for ganglioside stabilization and detection. Optimization of this technique has led to high sensitivity for the ions desorbed directly from the TLC plate. MALDI-FTMS experiments have been carried out on our home-built FT-ICR mass spectrometer with 7T magnet and Nd:YAG (UV) laser, frequency tripled to 355 nm, nitrogen laser (337 nm) and Er:YAG (IR) laser (2.94 um). The collision cooling gas raises the pressure in the ion source during the desorption-ionization event. Internal Calibration on Adjacent Samples (InCAS) is performed using standards desorbed from the stainless steel plate as calibrants. The sensitivity the has been obtained for the gangliosides desorbed from TLC is low fmol (total amount spotted on a TLC plate prior to separation). The use of InCAS has demonstrated that accuracy is not affected upon desorption of the analyte from uneven TLC plate surface and mass accuracy is usually 0.5-1.5 ppm for ganglioside standards. The effect of several parameters on molecule stabilization was studied, such as the type of the cooling gas, gas pulsing coordinating with ionization-desorption event, cooling gas pressure, duration of gas pulse, different laser intensities, focusing and beam profile. Soft IR-desorption of the gangliosides with urea as the matrix, together with cooling in the Vibrationally Cooled source eliminated sialic acid loss. The developed method is being applied to the samples from biological systems such as whole brain ganglioside mix, Leishmania lipids, ganglioside-rich lipid rafts from neuronal cells and HIV-protective glycolipids from human milk. Infrared multiphoton dissociation (CO2 laser, 10.7 um) and SORI-CAD are being used as complementary dissociation methods. During this year the original VC-MALDI system was rebuilt and its performance is being re-evaluated.