Analysis of phosphorylated peptides by ion mobility-mass spectrometry.

An ion mobility-mass spectrometry technique for rapid screening of phosphopeptides in protein digests is described. A data set of 43 sequences (ranging in mass from 400 to 3000 m/z) of model and tryptic peptides, including serine, threonine, and tyrosine phosphorylation, was investigated, and the data support our previously reported observation (Ruotolo, B. T.; Verbeck, G. F., IV; Thomson, L. M.; Woods, A. S.; Gillig, K. J.; Russell, D. H. J. Proteome Res. 2002, 1, 303.) that the drift time-m/z relationship for singly charged phosphorylated peptide ions is different from that for nonphosphorylated peptides. The data further illustrate that a combined data-dependent IM-MS/MS approach for phosphopeptide screening would have enhanced throughput over conventional MS/MS-based methodologies.

MALDI matrices for biomolecular analysis based on functionalized carbon nanomaterials.

When used in small molar ratios of matrix to analyte, derivatized fullerenes and single wall nanotubes are shown to be efficient matrices for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The mixing of an acidic functionalized fullerene with a solution of bioanalyte, depositing a dried droplet, and irradiating with a pulsed nitrogen laser yields protonated or cationized molecular ions. Derivatized fullerenes could offer several advantages over conventional MALDI matrices: a high analyte ionization efficiency, a small molar ratios (less than 1) of matrix/analyte, and a broader optical absorption spectrum, which should obviate specific wavelength lasers for MALDI acquisitions. The major disadvantage to the use of fullerenes is the isobaric interference between matrix and analyte ions; however, it is overcome by using MALDI-ion mobility time-of-flight (IM-oTOF) mass spectrometry to preseparate carbon cluster ions from bioanalyte ions prior to TOF mass analysis. However, an alternative to the dried droplet preparation of fullerene MALDI samples is the aerosolization of matrix-analyte solutions (or slurries) followed by impacting the aerosol onto a stainless surface. We also demonstrate that the fullerene matrices can be used to acquire spectra from rat brain tissue.