Speaker: Susanne C. Moyer, Department of Chemistry, Johns Hopkins University, Baltimore, MD 21205

Topic: Fragmentation of Phosphotyrosine-Containing Peptides by Atmospheric Pressure MALDI Ion Trap Mass Spectrometry - Video (running time 00:32:57) ^*

Place: Building 549, Auditorium, NCI at Frederick, Frederick, MD

Time: Tuesday, August 13, 2002, at 2:00 PM

Abstract: Recently, we combined atmospheric pressure matrix assisted laser desorption (AP-MALDI) with a commercial ion trap mass spectrometer (ITMS) [1]. Coupling the AP-MALDI source with an ion trap mass analyzer combines the benefits of MALDI sample preparation and simplicity of spectral analysis resulting from the production of predominantly singly charged ions, with the MSⁿ capabilities of the quadrupole ion trap mass spectrometer. This configuration has proven to be useful in obtaining structural information from peptides and protein digests as well as for the identification and characterization of posttranslational modifications [2].

The most recent version of our AP-MALDI source incorporates a new laser system (Bioscope UV+, Bioptic, Berlin, Germany) that provides both UV (Nd:YAG at 355 nm) and IR (Er:YAG at 2940 nm) radiation. Of particular interest to us is the possibility of utilizing liquid matrices for IR AP-MALDI/ITMS analysis. The 2940 nm wavelength of the IR laser is attractive as it coincides with the -OH stretching frequency, making it possible to use liquid matrices such as ethanol, glycerol, or water.

A number of phosphotyrosine-containing peptides have been studied in our laboratory using electrospray ionization (ESI) and AP-MALDI/ITMS [3]. In these studies, it was observed that those phosphotyrosine peptides that contained arginine or lysine residues in their sequences lost 98 Da under collision induced dissociation (CID) conditions in the ITMS. Conversely, phosphotyrosine peptides that do not contain arginine or lysine residues did not show a loss of phosphate in their CID spectra.

The development of an AP-MALDI source for a commercial ITMS instrument and its application to the analysis of tryptic digests, posttranslational modifications and noncovalent interactions will be presented. In addition, the use of this instrumentation in the characterization of fragmentation patterns of phosphotyrosine-containing peptides will be described.

1. Laiko VV, Moyer SC and Cotter RJ. "Atmospheric Pressure MALDI/Ion Trap Mass Spectrometry" Anal. Chem. 2000, 72, 5239-5243.
2. Moyer SC, Marzilli LA, Woods AS, Laiko VV, Doroshenko VM and Cotter RJ. "Atmospheric Pressure Matrix-Assisted Laser Desorption/Ionization (AP MALDI) On a Quadrupole Ion Trap Mass Spectrometer" Int. J. Mass Spectrom. in press.
3. Moyer SC, Cotter RJ and Woods AS. "Fragmentation of Phosphopeptides by Atmospheric Pressure MALDI and ESI/Ion Trap Mass Spectrometry" J. Am. Soc. Mass Spectrom. 2002, 13, 274-283.

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