Complete Assignment of the 360 MHz1H NMR Spectra of Some Oligomannosides

The system of sulfated alpha-(1-->3)-linked D-mannans from the red seaweed Nothogenia fastigiata: structures, antiherpetic and anticoagulant properties

Structural analysis of two xylomannans extracted from Nothogenia fastigiata was carried out. The results are consistent with the general pattern previously reported for other xylo-mannans of the same system, alpha-(1-->3)-linked D-mannans 2- and 6-sulfated and having single stubs of beta-(1-->2)-linked D-xylose, but one of the new samples contains a significant amount of 2,6-disulfated units. Both xylomannans studied are obtained as complexes with a beta-D-(1-->3)-, alpha-L-(1-->4)-galactan and a beta-D-(1-->3)-, beta-D-(1-->4)-'mixed linkage' xylan co-existing in the seaweed, a fact that limits the accuracy of the data determined. The structures of the galactan and the xylan are similar to those previously informed for this seaweed. The antiviral activity against four different herpes simplex viral strains and the anticoagulant properties of all the xylo-mannans of the system are reported.

A reinvestigation towards the conformation of methyl alpha-D-mannopyranosyl-(1-->6)-alpha-D-mannopyranoside by a combined ROE and molecular dynamics analysis

Conformational analysis of alpha-D-Man p-(1-->6)-alpha-D-Man p1-OMe, by a combination of extensive molecular dynamics calculations in water and ROE buildup series, afforded two main minima, namely, phi/psi = 95/-178 and phi/psi = 140/-185. Transitions between these minima are observed, which have not previously been demonstrated using other approaches. In contrast to literature data for the glycosidic linkage, describing equal populations of both the gg and the gt rotamers, it was found that the gg conformer is present to ca. 96%. The non-reducing mannosyl unit showed approximately a 1:1 ratio for the gg:gt equilibrium, in accordance with earlier reports.

Isolation and characterization of cell surface mutants of Candida albicans

Mutant strains of Candida albicans were obtained by selecting for cells that escaped agglutination by a polyclonal antiserum raised against standard C. albicans serotype A isolate B311. Mutants were obtained from strains B311 and B792 and from four strains isolated from patients with acquired immunodeficiency syndrome. All 15 tested mutants retained characteristic sugar assimilation patterns. All but one of the mutants retained the ability to form germ tubes and chlamydospores. Two mutants from an acquired immunodeficiency syndrome-derived isolate were deficient in binding complement ligands iC3b and C3d, whereas another mutant was deficient in binding ligand iC3b but not C3d. The hyphae of these three mutants lacked antigens when examined by Western immunoblotting with monoclonal antibody Ca-A, which detects several glycoproteins, including C3d-binding proteins. One of the complement-binding-deficient mutants was tested for its ability to colonize the gastrointestinal tract of rabbits but did not differ from the wild-type parent in site or degree of colonization. The proton magnetic resonance spectra of bulk mannan carbohydrate extracted from tested mutants showed the loss of a signal characteristic of the mannosyl alpha-PO4 linkage; each mutant also had a distinct pattern of other changes.

On the utility of 13C-n.m.r. spectroscopy in the identification of the primary structures of manno-oligosaccharides and glycopeptides

The utility of 13C-n.m.r. spectroscopy in the identification of the primary structures of mannose-containing glycans is investigated. Unlike 1H resonances where the chemical shifts reflect multiple short- and long-range effects, the chemical shifts of 13C resonances are dependent largely upon short-range effects classified as glycosylation (linkage) and substitution effects. These effects are parametized for glycans composed of mannose and encoded in a FORTRAN algorithm. Applications of this program to "unknown" sets of experimental chemical shifts for the resonances of anomeric carbons gave the following conclusions. (1) This program can be used to produce a sub-set of possible structures inclusive of the "known" structure. (2) For other than simple oligosaccharides, it is unlikely that a single structure is consistent with the data for anomeric carbons alone, even when the linkage composition of the glycan has been assessed from other spectral data. (3) When used in conjunction with other chemical techniques, this program can provide a powerful tool for primary analysis of the structure of mannose-containing glycans.