Array Of Oligosaccharides Research Articles

Photocatalytic conversion of cellulose into C5 oligosaccharides

Cellulose is made up of linear polymers of glucose monomers that could be a crucial source for valuable chemicals and sustainable liquid fuels. Cellulose is however, very stable and its conversion to a useful fuel or platform chemical products remains a significant challenge (Kimura et al 2015 Sci. Rep. 5 16266; Xia et al 2016 Nat. Commun. 7 11162). Photocatalysis is a versatile technology which has demonstrated potential for solar driven processes such as water splitting or solar fuels production and has also been applied to the degradation of pollutants in air and water and for the production of useful products from biomass. Here, we focus on the products that are produced from cellulose (a glucose (C6) based polymer) photocatalysis that compliment hydrogen production. Probing the initial steps via UV-TiO2 photocatalysis, we remarkably find that an array of oligosaccharides containing only five (C5) carbon units is initially produced. As the process continues, C6 oligo oligosaccharides grow to dominate. The photocatalytic process is generally not viewed as a controllable synthetic process; however, these findings show, on the contrary that photocatalysis at semiconductor surfaces can achieve novel reaction pathways yielding new products.

Oligosaccharides, neoglycoproteins and humanized plastics: their biocatalytic synthesis and possible medical applications

Glycobiology has become one of the fastest growing branches of the biological sciences. Glycomics, which is the study of an organism's entire array of oligosaccharides, is now emerging as the third informatics wave after genomics and proteomics. For example, it is possible to see this progress in the KEGG (Kyoto Encyclopedia of Genes and Genomes) database (http://www.genome.jp/kegg/pathway/map/map01110.html). The interest in this area stems from the realization that carbohydrates, especially oligosaccharides, and their interactions with proteins, play diverse informative roles in all organisms, and that more than half of all proteins are glycosylated. When the biological and pharmaceutical importance of glycoconjugates is considered, it is surprising how little glycobiotechnology has developed. This review reports the latest developments in the biocatalytic synthesis of oligosaccharides and glycoconjugates, with special attention paid to the glycosyltransferase approach. The second part of the review takes the 'conceptual approach' and covers possible medical applications of synthesized glycoconjugates. Various new examples of the conjugation of glyco-informative saccharide sequence to known pharmaceuticals or biomaterials are cited.

The N-linked oligosaccharides of the beta-subunit of rabbit gastric H,K-ATPase: site localization and identification of novel structures.

The gastric H,K-ATPase is responsible for acid secretion by parietal cells. Its beta-subunit is a glycoprotein which is exposed to the harsh, acidic environment of the stomach. The location and structural features of the N-linked oligosaccharides were determined using matrix-assisted laser desorption ionization mass spectrometry (MALDI/MS) (in conjunction with mass composition analysis and exoglycosidase digestions), Edman degradation, and monosaccharide composition analysis. All seven N-linked sequons at positions 99, 103, 130, 146, 161, 193, and 222 were fully glycosylated. An unusual restricted array of oligosaccharides was observed at individual Asn residues. Asn99 was modified exclusively with oligomannosidic-type structures (Man6GlcNAc2-Man8GlcNAc2). Asn193 contained both oligomannosidic (Man5GlcNAc2-Man8GlcNAc2) and lactosamine-type structures, indicating significant "leakiness" in the pathway which converts oligomannose to lactosamine-type at a single glycosylation site. MALDI/MS with collision-induced dissociation was required to demonstrate that sequons separated by a single residue (99Asn-Ile-Ser-Asp-Asn-Arg-Thr105) were modified with only oligomannose and lactosamine structures, respectively. Analysis of the total oligosaccharide pool using MALDI/MS and exoglycosidase analysis revealed 24 lactosamine species (bi-, tri-, and tetraantennary structures), with all branches terminated in alpha-linked Gal residues, most possessing a single Fuc residue. Nine novel oligosaccharides contained multiple alpha-linked Gal residues per branch. Bi- and triantennary structures, with and without lactosamine repeats, were observed at Asn146 and Asn161. Tetraantennary structures with lactosamine repeats were found only at Asn130, and this site also contained most of the structures with multiple alpha-linked Gal residues per branch.

Carbohydrates and the Pathogenesis of Mycoplasma pneumoniae Infection and AIDS—Some Observations and Speculations

Carbohydrate-mediated interactions are prominent in the pathobiology of human infection with Mycoplasma pneumoniae. The mycoplasma uses specific long-chain sialo-oligosaccharides at the host-cell surface as receptors. These sialo-oligosaccharides contain I antigen in their backbones, and they are richly expressed at the primary site of infection--the ciliated bronchial epithelium--and on erythrocytes. The autoantibodies of high titers directed to I antigen, cold hemagglutinins, frequently produced in this infection are therefore antibodies to receptors and may be triggered by an autoimmunogenic mycoplasma-receptor complex in which the lipid-rich microorganism serves as an adjuvant. Current interest is focused on the possibility that the course of infection with human immunodeficiency virus type 1 (HIV-1) may be exacerbated by coinfection with mycoplasmas. One mechanism for such potentiation would be specific interactions between the mycoplasmas and HIV-1 leading to a concentration of the virus at the mycoplasmal surface. The envelope glycoprotein gp120 of HIV-1 is richly decorated with an array of oligosaccharides whose biosynthesis is host cell directed. By an analogy with M. pneumoniae, I propose that recognition of carbohydrates by various mycoplasmal copathogens is a potential mechanism for interactions with HIV-1.

The initial stages of processing of protein-bound oligosaccharides in vitro.

Following the rapid enzymatic transfer of an oligosaccharide (GlcNAc2Man9Glc3) from a lipid carrier to endogenous protein acceptors in membrane preparations from NIL fibroblasts, the transferred oligosaccharide chain undergoes processing. Protein-bound oligosaccharides, released from the polypeptide backbone by treatment with endo-beta-N-acetylglucosaminidase H, were analyzed by gel filtration and by susceptibility to alpha-mannosidase digestion. The initial stages of this processing in vitro consist of sequential excision of 3 glucose residues prior to the removal of mannose residues. The array of oligosaccharides generated in vitro by membrane preparations from NIL cells appears to be identical with processed oligosaccharides derived in vivo in intact NIL cells.