The galactomannan (GM) produced extracellularly by Aspergillus fumigatus has been purified by a double sequential hydrazine-nitrous acid treatment of the ethanol precipitate of the culture filtrate. Nuclear magnetic resonance and gas-liquid chromatography-mass spectrometry analysis have been performed on intact GM, acid-hydrolyzed GM, and oligomers resulting from the acetolysis of the acid-hydrolyzed GM. Results show that

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This article describes oligosaccharide structures of mucin isolated from nude mouse xenograft tumors produced by LS174T-HM7 cells, a subline of the human colon carcinoma LS174T with higher metastatic tendency and higher mucin production. A striking feature of the oligosaccharides of the LS174T-HM7 xenograft tumor mucin was a predominance of sulfated Lewis X determinants: HSO 3 -Gal␤1-4(Fuc␣1-3)GlcNAc. In addition to one previously known saccharide with one sulfated Lewis X determinant, the HM7 xenograft tumor mucin contained multiple novel structures containing one, two, or three sulfated Lewis X determinants. This determinant, known to act as a selectin ligand, has been found previously in minor saccharide components of human milk as well as mucins, but never before as a predominant structure in one mucin source.

The cell-associated glucans produced by Burkholderia solanacearum and Xanthomonas campestris pv. citri were isolated by trichloroacetic acid treatment and gel permeation chromatography. The compounds obtained were characterized by compositional analysis, matrix-assisted laser desorption ionization mass spectrometry, and high-performance anion-exchange chromatography. B. solanacearum synthesizes only a neutral cyclic glucan containing 13 glucose residues, and X. campestris pv. citri synthesizes a neutral cyclic glucan containing 16 glucose residues. The two glucans were further purified by high-performance anion-exchange chromatography. Methylation analysis revealed that these glucans are linked by 1,2-glycosidic bonds and one 1,6-glycosidic bond. Our 600-MHz homonuclear and 1 H- 13C heteronuclear nuclear magnetic resonance experiments revealed the presence of a single ␣-1,6-glycosidic linkage, whereas all other glucose residues are ␤-1,2 linked. The presence of this single ␣-1,6 linkage, however, induces such structural constraints in these cyclic glucans that all individual glucose residues could be distinguished. The different anomeric proton signals allowed complete sequence-specific assignment of both glucans. The structural characteristics of these glucans contrast with those of the previously described osmoregulated periplasmic glucans.Cell surface carbohydrates are involved in bacterium-plant interactions in both pathogenesis and symbiosis (6,7,15,16). Three fundamentally distinct categories of carbohydrate structures can be observed in gram-negative bacteria: exopolysaccharides can form a cell-associated capsule or a fluidal slime, lipopolysaccharides are an intrinsic part of the outer membrane, and osmoregulated periplasmic glucans (OPG) were only recently recognized as general constituents of the gramnegative envelopes and are particularly abundant when the medium osmolarity is low. The latter compounds were essentially studied in members of the family Rhizobiaceae, where they are known as cyclic ␤-glucans (6).A number of studies have demonstrated that Agrobacterium and Rhizobium species synthesize OPG with similar structures (for reviews, see references 6 and 12). In both genera, OPG are composed of a cyclic ␤-1,2-linked backbone containing 17 to 40 glucose residues which can be substituted by sn-1-phosphoglycerol (20), as well as by methylmalonic acid or succinic acid (13). OPG-defective mutants of Rhizobium meliloti form ineffective white pseudonodules on alfalfa (11), and OPG-defective mutants of Agrobacterium tumefaciens are avirulent (28). Extracts of Bradyrhizobium spp. revealed the presence of cyclic OPG linked by both ␤-1,3-and ␤-1,6-glycosidic bonds, containing 10 to 13 glucose residues (21), which can be substituted by phosphocholine (29). OPG-defective mutants of Bradyrhizobium japonicum formed ineffective nodules on soybean plants (5). Several researchers have emphasized the cyclic character of these OPG, which was supposed to permit inclusion complexes with hydrophobic guest molecules (6)...

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Mucin glycopeptides were prepared from the salivary mucins of 20 healthy donors with blood group O. The carbohydrate chains of the high-molecular-weight mucins were released by alkaline borohydride treatment. Neutral and monosialylated oligosaccharide-alditols were purified by ion-exchange chromatography, gel filtration, and HPLC. The structures of the oligosaccharide-alditols were determined by high-resolution 1H-NMR spectroscopy in combination with fast atom bombardment mass spectrometry and methylation analysis. Thirty-seven oligosaccharide-alditols were characterized and illustrate the extreme diversity of the salivary mucins carbohydrate chains. This diversity might represent a mosaic of bacterial adhesion sites and be involved in the early events of the nonimmune defense of the oral cavity. Among these 37 oligosaccharide-alditols, 31 have not been previously described in human saliva and five of these are novel structures: [formula: see text]

We describe the structure of a small cyclic peptide Cys-Leu-Pro-Arg-Glu-Pro-Gly-Leu-Cys containing two non-vicinal prolines. A previous HPLC analysis showed two well-resolved peaks at low temperature, and the hypothesis of slow conformational equilibrium due to steric constraints induced by cyclization was presented (Gesquiere, J-C.; Diesis, E.; Cung, M. T.; Tartar, A. J. Chromatogr. 1989, 478, 121). Our NMR study shows that at least three conformations of the peptide are present in solution: a major form which is the all-trans conformer and two minor forms where the peptide bonds Leu-Pro or Glu-Pro are in the cis conformation. The first HPLC peak was shown to contain the trans-trans and trans-cis forms of the peptide whereas the second HPLC peak contains the cis-trans form. The combined use of HPLC and NMR techniques led to the kinetic parameters characterizing the isomerization. The solution structure of the trans-trans peptide was determined by NMR spectroscopy and showed a predominant structural role for the proline in position three and for the cysteine bridge. Reduction of the disulfide bridge leads to a peptide where the cis and trans forms of both proline residues are still observable by NMR but where cis/trans isomerization of Pro3 is too fast to be detected on the HPLC time scale.

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