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Articles by S. W Wu
Total Records ( 13 ) for S. W Wu
  N Suzuki , T. H Su , S. W Wu , K Yamamoto , K. H Khoo and Y. C Lee

We previously showed that the expression of (Gal1-4Gal)-bearing glycoproteins among birds is related to their phylogeny. However, precise structures of (Gal1-4Gal)-containing N-glycans were only known for pigeon egg white glycoproteins and IgG. To compare structural features of (Gal1-4Gal)-containing N-glycans from other species, we analyzed N-glycans of gull egg white (GEW)-glycoproteins, ovomucoid, and ovotransferrin, and gull egg yolk IgG by HPLC, mass spectrometry (MS), and MS/MS analyses. GEW-glycoproteins included neutral, monosialyl, and disialyl N-glycans, and some of them contained Gal1-4Gal sequences. Bi-, tri-, and tetra-antennary oligosaccharides that lacked bisecting GlcNAc were the major core structures, and incomplete -galactosylation and sialylation as well as the presence of diLacNAc on the branches generated microheterogeneity of the N-glycan structures. Moreover, unlike pigeon egg white glycoproteins, the major sialylation in GEW-glycoproteins is 2,3-, but not 2,6-linked sialic acids (NeuAc). In addition to the complex-type oligosaccharide, hybrid-type oligosaccharides that lack bisecting GlcNAc were also abundant in GEW-glycoproteins. Gull egg yolk IgG also contained Gal1-4Galβ1-4GlcNAcβ1- sequences, but unlike pigeon IgG, no Gal1-4Galβ1-4Galβ1-4GlcNAcβ1- sequence was detected. Bi- and tri-antennary complex-type oligosaccharides with bisecting GlcNAc and with core fucosylation as well as high-mannose-type oligosaccharides were the major structures in gull IgG. Our data indicated that some N-glycans from both GEW-glycoproteins and gull IgG contain the Gal1-4Galβ1-4GlcNAcβ1- sequence, but the ratio of -Gal-capped residues to non--Gal-capped residues in the nonreducing termini of N-glycans is much lower than that in those of pigeon glycoproteins.

  S. Y Yu , S. W Wu , H. H Hsiao and K. H. Khoo

Sulfate modifications on terminal epitopes of N- and O-glycans have increasingly been implicated as critical determinants mediating a diverse range of biological recognition functions. To address these low abundance but important sulfated glycans, and the sulfoglycome in general, further development of enrichment strategies and enabling mass spectrometry (MS)-based mapping techniques are needed. In this report, we demonstrate that the sulfated glycans, with and without additional sialylation, can be successfully permethylated by the sodium hydroxide slurry method and be distinguished from phosphorylated glycans by virtue of this derivatization. In conjunction with simple microscale postderivatization fractionation steps, permethyl derivatives fully retaining the negatively charged sulfate moiety and separated from the nonsulfated ones, can be efficiently detected and sequenced de novo by advanced MS/MS in the positive-ion mode. In particular, we show that the highly sequence and linkage informative high energy collision induced dissociation (CID) MS/MS afforded by MALDI-TOF/TOF can be extended to sulfoglycomic applications. The sulfated parent ion selected for CID MS/MS was found to mostly retain the sulfate moiety and therefore allow efficient fragmentation via the usual array of glycosidic, cross ring, and concerted double cleavages. Collectively, the optimized strategy enables a high sensitivity detection and critical mapping of the sulfoglycome such as the one derived from lymph node tissues or cell lines in both negative and positive-ion modes. Novel sulfated epitopes were identified from a crude mouse lymph node preparation, which fully attested to the practical utility of the methodology developed.

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