Profiling glycans in human serum and egg jelly coats of Xenopus borealis with mass spectrometry.

摘要

In the first chapter over 50 O-linked oligosaccharides chemically released from egg jelly of Xenopus borealis are analyzed with MALDI MS; approximately 30 oligosaccharides are structurally elucidated by infrared multiphoton dissociation (IRMPD) MS. Coupled with specific and targeted exoglycosidases, MS analyses further determined structures of 12 glycans. Surprisingly, there are no anionic glycans observed in the egg jelly of the species, in contrast to its relatives, X. laevis and X. tropicalis.; Chapter 2 describes collision-induced dissociation (CID), a commonly used tandem MS technique, as an efficient analytical tool in the structure determination of O-linked glycans. The structural information of glycans can be obtained from fragment ions in CID MS spectra.; The use of infrared multiphoton dissociation (IRMPD), another tandem MS technique, to obtain structural information for O- and N-linked oligosaccharides is illustrated in Chapter 3. The richer fragmentation of glycans with IRMPD allows rapid and efficient structure assignments. The IRMPD and CID behaviors of oligosaccharides are compared.; Chapter 4 covers the characterization of glycosylation changes between pooled normal control and pooled ovarian cancer sera in some specific glycoproteins with an approach combining protein biochemistry and MALDI MS analysis. Four glycoproteins have been identified using in-gel trypsin digestion and protein database searching. In ovarian cancer sera, apolipoprotein B-100 precursor (370 kD) is apparently down-regulated. MS analyses of glycans in identified glycoproteins show that there are glycosylation changes between normal and cancer patients in each of the glycoproteins.; A glycomic approach is demonstrated in Chapter 5 to identify unique glycans in human serum as potential markers for ovarian cancer by rapidly profiling the globally released oligosaccharides. Changes in protein glycosylation are monitored and analyzed by MALDI-FT MS. It is shown that at least fifteen unique glycan markers are present in all cancer patients but absent in normal individuals. The structures of some glycan markers are assigned putatively by IRMPD MS. The approach has been compared with the CA125 diagnostic test, a currently employed clinical blood test for ovarian cancer.