Assignment of 1H and 13C NMR chemical shifts of a d-mannan composed of α-(1 → 2) and α-(1 → 6) linkages obtained from Candida kefyr IFO 0586 strain

α-D-mannan from Aureobasidium pullulans (CCMB 324): optimization extraction

Mannans has been attracted the interest in various sectors due to its promising applications. The low toxicity of mannans allows for their use in cosmetics, pharmaceutical, and biomedical industries. In this study, the α-D-mannan extraction conditions from Aureobasidium pullulans by alkaline extraction were optimized using a Box-Behnken design (BBD). The effect of temperature (°C), pH and extraction time (hours) on the yield of α-mannan was investigated. The conditions that produced the highest yield (26%) were a temperature of 92 °C, extraction time of 3 h and pH 13. In addition, the α-D-mannan structure was confirmed by methylation analysis, 1D and 2D NMR spectroscopic analysis, and GC-MS.

Isolation, Physicochemical Characterization, Labeling, and Biological Evaluation of Mannans and Glucans

The cell wall contains mannans and glucans that are recognized by the host immune system. In this chapter, we will describe the methods to isolate mannans and glucans from the C. albicans cell wall. In addition, we describe how to determine purity, molecular size, and structure of the mannans and glucans. We also detail how to prepare the carbohydrates for in vitro, ex vivo, or in vivo use by describing endotoxin removal (depyrogenation), derivatization, and labeling and evaluation of bioactivity.

Fast MAS 1H-13C correlation NMR for structural investigations of plant cell walls

Plant cell walls consist of a mixture of polysaccharides that render the cell wall a strong and dynamic material. Understanding the molecular structure and dynamics of wall polysaccharides is important for understanding and improving the properties of this energy-rich biomaterial. So far, solid-state NMR studies of cell wall structure and dynamics have solely relied on ¹³C chemical shifts measured from 2D and 3D correlation experiments. To increase the spectral resolution, sensitivity and upper limit of measurable distances, it is of interest to explore ¹H chemical shifts and ¹H-detected NMR experiments for analyzing cell walls. Here we demonstrate 2D and 3D ¹H-¹³C correlation experiments at both moderate and fast MAS frequencies of 10-50 kHz to resolve and assign ¹H chemical shifts of matrix polysaccharides in Arabidopsis primary cell walls. Both ¹³C-detected and ¹H-detected experiments are implemented and are shown to provide useful and complementary information. Using the assigned ¹H chemical shifts, we measured long-range correlations between matrix polysaccharides and cellulose using ¹H-¹H instead of ¹³C-¹³C spin diffusion, and the 2D experiments can be conducted with either ¹³C or ¹H detection.

Corrosive extracellular polysaccharides of the rock-inhabiting model fungus Knufia petricola

Melanised cell walls and extracellular polymeric matrices protect rock-inhabiting microcolonial fungi from hostile environmental conditions. How extracellular polymeric substances (EPS) perform this protective role was investigated by following development of the model microcolonial black fungus Knufia petricola A95 grown as a sub-aerial biofilm. Extracellular substances were extracted with NaOH/formaldehyde and the structures of two excreted polymers studied by methylation as well as NMR analyses. The main polysaccharide (~ 80%) was pullulan, also known as α-1,4-; α-1,6-glucan, with different degrees of polymerisation. Αlpha-(1,4)-linked-Glcp and α-(1,6)-linked-Glcp were present in the molar ratios of 2:1. A branched galactofuromannan with an α-(1,2)-linked Manp main chain and a β-(1,6)-linked Galf side chain formed a minor fraction (~ 20%). To further understand the roles of EPS in the weathering of minerals and rocks, viscosity along with corrosive properties were studied using atomic force microscopy (AFM). The kinetic viscosity of extracellular K. petricola A95 polysaccharides (≈ 0.97 × 10⁻⁶ m² s⁻¹) ranged from the equivalent of 2% (w/v) to 5% glycerine, and could thus profoundly affect diffusion-dominated processes. The corrosive nature of rock-inhabiting fungal EPS was also demonstrated by its effects on the aluminium coating of the AFM cantilever and the silicon layer below.

Necroptosis mediates the antineoplastic effects of the soluble fraction of polysaccharide from red wine in Walker-256 tumor-bearing rats

Polysaccharides are substances that modify the biological response to several stressors. The present study investigated the antitumor activity of the soluble fraction of polysaccharides (SFP), extracted from cabernet franc red wine, in Walker-256 tumor-bearing rats. The monosaccharide composition had a complex mixture, suggesting the presence of arabinoglactans, mannans, and pectins. Treatment with SFP (30 and 60mg/kg, oral) for 14days significantly reduced the tumor weight and volume compared with controls. Treatment with 60mg/kg SFP reduced blood monocytes and neutrophils, reduced the tumor activity of N-acetylglucosaminidase, myeloperoxidase, and nitric oxide, increased blood lymphocytes, and increased the levels of tumor necrosis factor α (TNF-α) in tumor tissue. Treatment with SFP also induced the expression of the cell necroptosis-related genes Rip1 and Rip3. The antineoplastic effect of SFP appears to be attributable to its action on the immune system by controlling the tumor microenvironment and stimulating TNF-α production, which may trigger the necroptosis pathway.

Mannan structural complexity is decreased when Candida albicans is cultivated in blood or serum at physiological temperature

The Candida albicans cell wall provides an architecture that allows for the organism to survive environmental stress as well as interaction with host tissues. Previous work has focused on growing C. albicans on media such as Sabouraud or YPD at 30°C. Because C. albicans normally colonizes a host, we hypothesized that cultivation on blood or serum at 37°C would result in structural changes in cell wall mannan. C. albicans SC5314 was inoculated onto YPD, 5% blood, or 5% serum agar media three successive times at 30°C and 37°C, then cultivated overnight at 30°C in YPD. The mannan was extracted and characterized using 1D and 2D (1)H NMR techniques. At 30°C cells grown in blood and serum contain less acid-stable terminal β-(1→2)-linked d-mannose and α-(1→2)-linked d-mannose-containing side chains, while the acid-labile side chains of mannan grown in blood and serum contain fewer β-Man-(1→2)-α-Man-(1→ side chains. The decrement in acid-stable mannan side chains is greater at 37°C than at 30°C. Cells grown on blood at 37°C show fewer →6)-α-Man-(1→ structural motifs in the acid-stable polymer backbone. The data indicate that C. albicans, grown on media containing host-derived components, produces less complex mannan. This is accentuated when the cells are cultured at 37°C. This study demonstrates that the C. albicans cell wall is a dynamic and adaptive organelle, which alters its structural phenotype in response to growth in host-derived media at physiological temperature.

Synthesis of a mannose heptasaccharide existing in baker's yeast, Saccharomyces cerevisiae X2180-1A wild-type strain

A mannose heptasaccharide existing in baker's yeast, Saccharomyces cerevisiae X2180-1A wild-type strain, was effectively synthesized as its allyl glycoside via TMSOTf-promoted condensation of a disaccharide donor 13 with a pentasaccharide acceptor 12, followed by deprotection. The pentasaccharide 12 was constructed by coupling of 2,3,4,6-tetra-O-benzoyl-alpha-D-mannopyranosyl-(1-->3)-2,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl-(1-->2)-3,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl-(1-->2)-3,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl trichloroacetimidate (9) with allyl 6-O-acetyl-3,4-di-O-benzoyl-alpha-D-mannopyranoside (10), followed by deacetylation. The tetrasaccharide 9 was obtained by coupling of 2,3,4,6-tetra-O-benzoyl-alpha-D-mannopyranosyl-(1-->3)-2,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl trichloroacetimidate (5) with allyl 3,4,6-tri-O-benzoyl-alpha-D-mannopyranosyl-(1-->2)-3,4,6-tri-O-benzoyl-alpha-D-mannopyranoside (6), followed by deallylation and trichloroacetimidation. The disaccharides 6 and 13 were readily obtained by known methods.

New exopolysaccharides produced by Aureobasidium pullulans grown on glucosamine

The polysaccharides produced by Aureobasidium pullulans, grown using glucosamine as the carbon source, were investigated by means of methylation analysis, affinity chromatography and NMR spectroscopy. The results indicated that, besides a small amount of pullulan, this micro-organism was capable of producing-in low yields-mixtures of at least two different complex polysaccharides containing mainly mannose and galactose. (1)H NMR spectra of two fractions obtained by lectin affinity chromatography indicated that one polymer was constituted exclusively of mannose residues while the other contained both galactofuranosyl and mannopyranosyl residues.

Chemical structure of two phytotoxic exopolysaccharides produced by Phomopsis foeniculi

The two main exocellular polysaccharides produced in vitro by Phomopsis foeniculi, a fungal pathogen of fennel, were isolated and characterized by chemical and spectroscopic methods as a galactan with the known structure [-->6)-beta-D-Galf-(1-->5)-beta-D- Galf-(1-->5)-beta-D-Galf-(1-->]n and a mannan. The latter consists of a backbone of alpha-(1-->6)-linked mannopyranose units. Almost all of these are branched at the 2 position with arms containing 2- and 3-linked mannopyranose units. The crude polysaccharide fraction and its components, galactan and mannan, showed phytotoxic effects, i.e. chlorosis, necrosis and/or wilting, on fennel and on two non-host plants, tobacco and tomato.

NMR assignment of the galactomannan of Candida lipolytica

The chemical structure of the cell wall galactomannan of Candida lipolytica was analyzed using two-dimensional NMR techniques without chemical fragmentation. The H-1-H-2-correlated cross-peaks of the galactomannan indicated that it consists of an alpha-1,6-linked mannan backbone moiety with side chains. A sequential NMR assignment of the side chains through nuclear Overhauser effect (NOE) cross-peaks indicated that the triose side chain contains an alpha-1,2-linked galactopyranose unit at the non-reducing terminal. The structure was significantly different from the galactomannan of Trichophyton. The molar ratio of the side chains calculated from the H-1 signal dimensions indicated that ca. 45% of the backbone alpha-1,6-linked mannose units are not substituted with side chains and are responsible for the reactivity of the galactomannan with factor 9 serum.

Structure of a cell wall mannan from the pathogenic yeast, Candida catenulata: assignment of 1H nuclear magnetic resonance chemical shifts of the inner alpha-1,6-linked mannose residues substituted by a side chain

We performed an enzyme-linked immunosorbent assay of the cell wall mannan purified from the pathogenic yeast, Candida catenulata, using antisera to factors of the genus Candida. The results suggest that mannan possesses a linear backbone consisting of alpha-1, 6-linked mannose residues and side chains possessing nonreducing terminal alpha-1,2- and alpha-1,3-linked mannose residues. The chemical structure of the mannan was analyzed by two-dimensional homonuclear Hartmann-Hahn and two-dimensional nuclear Overhauser enhancement and exchange spectroscopy. The sequential assignments of the cross-peaks caused by J-coupling and the nuclear Overhauser effect from these terminal mannose residues demonstrate that the H1 signal of an inner alpha-1,6-linked mannose residue substituted by an alpha-oligomannosyl side chain or a single mannose through the C-2 position in an alpha-anomer configuration undergoes a significant downfield shift (delta delta = 0.16 or 0.19 ppm, respectively) compared with that of unsubstituted residues. We therefore propose the exact overall structure of the antigenic mannan obtained from C. catenulata. The assignment data in the present study are useful for the determination of the exact overall structure of various yeast mannans using the two-dimensional nuclear magnetic resonance analysis without the need for harsh procedures.

Identification of the antigenic determinants of factors 8, 9, and 34 of genus Candida

We investigated the antigenic determinants of factors 8, 9, and 34 of the genus Candida among pathogenic yeasts by enzyme-linked immunosorbent assay (ELISA) using mannans of Saccharomyces cerevisiae wild type and mutant types, mnn 1-mnn 4 and mnn 2. Results of ELISA including antisera against the antigenic factors of genus Candida (Candida Check, latron; FAbs) indicated that these three types of mannan distinctly react with FAbs 34, 8 and 9, respectively. To identify the recognition sites of these FAbs, we compared the ability of various oligosaccharides to inhibit the binding of the mannans to FAbs. The results indicated that FAb 34 preferentially recognizes linear side chains containing a non-reducing terminal alpha-1,3-linked mannose residue, Man(alpha)1 --> 3Man(alpha)1 --> (2Man(alpha)1 --> )n(2Man) (n > or = 0), and that one of the recognition sites of FAb 9 is linear alpha-1,6-linked oligomannosyl series, Man(alpha)1 --> (6Man(alpha)1 --> )n(6Man) (n > or = 2). On the other hand, the recognition site of FAb 8 apparently consisted of two alpha-1,2-linked oligomannosyl side chains and an alpha-1,6-linked mannose residue that originated from the mannan backbone, Man(alpha)1 --> 2Man(alpha)1 --> 2(Man(alpha)1 -->2Man(alpha)1 --> 6)Man.