ELECTROSPRAY-IONIZATION TANDEM MASS-SPECTROMETRIC ANALYSIS OF SULFATIDE - DETERMINATION OF FRAGMENTATION PATTERNS AND CHARACTERIZATION OF MOLECULAR-SPECIES EXPRESSED IN BRAIN AND IN PANCREATIC-ISLETS

The sphingolipid sulfatide is a component of myelin and some non-neuro nal cells. Antibodies to sulfatide occur in some patients with autoimm une neuropathies and in patients with insulin-dependent diabetes melli tus (IDDM) caused by immunologic destruction of insulin-secreting panc reatic islet beta-cells. Distinct sulfatide molecular species may diff er in immunogenicity, and facile means to identify sulfatide species i n islets and other tissues obtainable in only small amounts could be u seful. Electrospray ionization mass spectrometry (ESI/MS) permits stru ctural determination of small quantities of phospholipids and is appli ed here to sulfatide analysis. We find that sulfatide standards are re adily analyzed by negative ion ESI/MS, and tandem mass spectra of indi vidual species exhibit some ions common to all species and other ions that reflect distinct fatty acid substituents in different sulfatide m olecules. A signature ion cluster resulting from cleavage directed by the alpha-hydroxy group of sulfatide species with a hydroxylated fatty acid substituent identifies such species. Sulfatide profiles in tissu e lipid extracts can be obtained by ESI/MS/MS scanning for common sulf atide ions and for ions reflecting fatty acid substituents. Islets are demonstrated to contain sulfatide and to exhibit a profile of species different from that of brain. (C) 1998 Elsevier Science B.V.