Dectin-2-mediated signaling triggered by the cell wall polysaccharides of Cryptococcus neoformans.

Cryptococcus neoformans is rich in polysaccharides of the cell wall and capsule. Dectin-2 recognizes high-mannose polysaccharides and plays a central role in the immune response to fungal pathogens. Previously, we demonstrated Dectin-2 was involved in the activation of dendritic cells upon stimulation with C. neoformans, suggesting the existence of a ligand recognized by Dectin-2. In the present study, we examined the cell wall structures of C. neoformans contributing to the Dectin-2-mediated activation of immune cells. In a NFAT-GFP reporter assay of the reported cells expressing Dectin-2, the lysates, but not the whole yeast cells, of an acapsular strain of C. neoformans (Cap67) delivered Dectin-2-mediated signaling. This activity was detected in the supernatant of ß-glucanase-treated Cap67 and more strongly in the semi-purified polysaccharides of this supernatant using ConA-affinity chromatography (ConA-bound fraction), in which a large amount of saccharides, but not protein, were detected. Treatment of this supernatant with periodic acid and the addition of excessive mannose, but not glucose or galactose, strongly inhibited this activity. The ConA-bound fraction of the ß-glucanase-treated Cap67 supernatant was bound to Dectin-2-Fc fusion protein in a dose-dependent manner and strongly induced the production of interleukin-12p40 and tumour necrosis factor-α by dendritic cells; this was abrogated under the Dectin-2-deficient condition. Finally, 98 kDa mannoprotein (MP98) derived from C. neoformans showed activation of the reporter cells expressing Dectin-2. These results suggested that a ligand with mannose moieties may exist in the cell walls and play a critical role in the activation of dendritic cells during infection with C. neoformans.

GfsA is a ß1,5-galactofuranosyltransferase involved in the biosynthesis of the galactofuran side chain of fungal-type galactomannan in Aspergillus fumigatus.

Previously, we reported that GfsA is a novel galactofuranosyltransferase involved in the biosynthesis of O-glycan, the proper maintenance of fungal morphology, the formation of conidia and anti-fungal resistance in Aspergillus nidulans and A. fumigatus (Komachi Y et al., 2013. GfsA encodes a novel galactofuranosyltransferase involved in biosynthesis of galactofuranose antigen of O-glycan in Aspergillus nidulans and Aspergillus fumigatus. Mol. Microbiol. 90:1054-1073). In the present paper, to gain an in depth-understanding of the enzymatic functions of GfsA in A. fumigatus (AfGfsA), we established an in vitro assay to measure galactofuranosyltransferase activity using purified AfGfsA, UDP-α-d-galactofuranose as a sugar donor, and p-nitrophenyl-ß-d-galactofuranoside as an acceptor substrate. LC/MS, 1H-NMR and methylation analyses of the enzymatic products of AfGfsA revealed that this protein has the ability to transfer galactofuranose to the C-5 position of the ß-galactofuranose residue via a ß-linkage. AfGfsA requires a divalent cation of manganese for maximal activity and consumes UDP-α-d-galactofuranose as a sugar donor. Its optimal pH range is 6.5-7.5 and its optimal temperature range is 20-30°C. 1H-NMR, 13C-NMR and methylation analyses of fungal-type galactomannan extracted from the ∆AfgfsA strain revealed that AfGfsA is responsible for the biosynthesis of ß1,5-galactofuranose in the galactofuran side chain of fungal-type galactomannan. Based on these results, we conclude that AfGfsA acts as a UDP-α-d-galactofuranose: ß-d-galactofuranoside ß1,5-galactofuranosyltransferase in the biosynthetic pathway of galactomannans.

Significant structural change in both O- and N-linked carbohydrate moieties of the antigenic galactomannan from Aspergillus fumigatus grown under different culture conditions.

Invasive aspergillosis is an important cause of morbidity and mortality in immunocompromised patients. Diagnosis of this infection frequently employs detection of the circulating galactomannan in the patient serum using enzyme immunoassay (EIA), a highly sensitive and specific system. Although there are many structural studies of the galactomannan of Aspergillus fumigatus, some inconsistencies are present in these results. In this study, to clarify the relationship between the growth conditions and structure of the galactomannans, we cultured A. fumigatus using two distinct yeast/fungal cultivation media, i.e. the yeast extract-peptone-dextrose (YPD) medium and yeast nitrogen base (YNB) medium. Galactomannans prepared from the resulting culture supernatants were structurally characterized by (1)H and (13)C nuclear magnetic resonance, methylation analysis, acetolysis and α-mannosidase degradation. These assays revealed that the galactomannan from the YPD cultivation had short ß-1,5-linked galactofuranose (Galf) oligosaccharide chains in both the O- and N-linked carbohydrate moieties, while the galactomannan from the YNB cultivation incorporated long Galf oligosaccharide chains. The galactomannans derived from the two culture conditions significantly differed in reactivity based on the EIA diagnostic system. We also demonstrated the presence of a novel Galf-containing branched oligosaccharide in the O-linked moiety.

Mechanism of high-affinity abscisic acid binding to PYL9/RCAR1.

Arabidopsis receptors of abscisic acid (ABA), the key plant hormone for adaptation to water stress, comprise 14 PYR/PYLs/RCARs proteins classified into three subfamilies I, II, and III, which suggests functional differentiation. Although their monomer-dimer equilibria may be correlated with differences in their ABA-binding affinities, how the dimerization decreases the affinity is unclear. Comparative structural and binding studies between PYL9, which is a representative of high-affinity subfamily I, and low-affinity members of subfamily III reveals that the nonpolar triplet (Ile110, Val162, and Leu165) and Pro64 contribute to enhance ABA-binding affinity by inducing a shift of the ABA carboxyl group to form additional direct hydrogen bonds with conserved Asn169. Our mutation studies of PYL1 successfully produced a monomeric mutant PYL1 exhibiting low ABA affinity and also a dimeric mutant PYL1 exhibiting high ABA-binding affinity, suggesting that dimer formation of ABA receptors is not essential for their low ABA-binding affinity. Our study contributes toward establishing the structural basis for the higher ABA-binding affinity of the subfamily receptors and provides a clue for understanding the broad spectrum of hormone actions in plants manifested by the different hormone-binding affinity of multiple receptors.

Heterologous Production of Hyaluronic Acid in an ε-Poly-L-Lysine Producer, Streptomyces albulus.

Hyaluronic acid (HA) is used in a wide range of medical applications, where its performance and therapeutic efficacy are highly dependent on its molecular weight. In the microbial production of HA, it has been suggested that a high level of intracellular ATP enhances the productivity and molecular weight of HA. Here, we report on heterologous HA production in an ε-poly-l-lysine producer, Streptomyces albulus, which has the potential to generate ATP at high level. The hasA gene from Streptococcus zooepidemicus, which encodes HA synthase, was refactored and expressed under the control of a late-log growth phase-operating promoter. The expression of the refactored hasA gene, along with genes coding for UDP-glucose dehydrogenase, UDP-N-acetylglucosamine pyrophosphorylase, and UDP-glucose pyrophosphorylase, which are involved in HA precursor sugar biosynthesis, resulted in efficient production of HA in the 2.0 MDa range, which is greater than typical bacterial HA, demonstrating that a sufficient amount of ATP was provided to support the biosynthesis of the precursor sugars, which in turn promoted HA production. In addition, unlike in the case of streptococcal HA, S. albulus-derived HA was not cell associated. Based on these findings, our heterologous production system appears to have several advantages for practical HA production. We propose that the present system could be applicable to the heterologous production of a wide variety of molecules other than HA in the case their biosynthesis pathways require ATP in vivo.

An immune-adrenergic pathway induces lethal levels of platelet-activating factor in mice.

Acute immune responses with excess production of cytokines, lipid/chemical mediators, or coagulation factors, often result in lethal damage. In addition, the innate immune system utilizes multiple types of receptors that recognize neurotransmitters as well as pathogen-associated molecular patterns, making immune responses complex and clinically unpredictable. We here report an innate immune and adrenergic link inducing lethal levels of platelet-activating factor. Injecting mice with toll-like receptor (TLR) 4 ligand lipopolysaccharide (LPS), cell wall N-glycans of Candida albicans, and the α2-adrenergic receptor (α2-AR) agonist medetomidine induces lethal damage. Knocking out the C-type lectin Dectin-2 prevents the lethal damage. In spleen, large amounts of platelet-activating factor (PAF) are detected, and knocking out lysophospholipid acyltransferase 9 (LPLAT9/LPCAT2), which encodes an enzyme that converts inactive lyso-PAF to active PAF, protects mice from the lethal damage. These results reveal a linkage/crosstalk between the nervous and the immune system, possibly inducing lethal levels of PAF.

Evaluation of interactions between metal ions and nonionic surfactants in high-concentration HCl using low-pressure high-performance liquid chromatography with low-flow-resistance polystyrene-based monolithic column.

A method for evaluating the interactions between metal ions and nonionic surfactants in aqueous solutions containing high-concentration HCl, using gas pressure-driven low-pressure high-performance liquid chromatography (LP-HPLC) as a highly acid-resistant HPLC system, was developed. To construct the LP-HPLC for this purpose, poly(styrene-co-divinylbenzene)-based low-flow-resistance monolithic columns tolerant to highly acidic conditions were prepared using low-conversion thermal polymerization. Thermal polymerization at 65 °C for 1.5 h (monomer conversions, 33% for styrene and 59% for divinylbenzene) allowed preparation of a column with both high separation efficiency (around 60,000 plates m(-1) for alkylbenzenes) and a quite low back pressure of 0.14 MPa at a linear flow rate of 1 mm s(-1) (2.8 × 10(-13) m(2) in permeability). The base column prepared under the above conditions was coated with a nonionic surfactant, polyoxyethylene nonylphenyl ether (PONPE, average oxyethylene unit numbers (n) = 3, 7.5, 15, and 20), and used for evaluation of the interactions between PONPEs and metal ions in 6 M HCl. The interactions between PONPEs and Au(III), Ga(III), Fe(III), Zn(II), and Cu(II) were successfully evaluated using both breakthrough and chromatographic methods. Furthermore, a study of the effect of the polyoxyethylene (POE) chain length revealed that the use of PONPE with the longer POE moiety enhanced the magnitude of the interaction together with the increase in the amount of oxyethylene (OE) units coated on the monolith. Moreover, the interactions of metal ions with a single OE unit were almost constant in the range of n = 7.5-20, whereas the suppression of the interaction between Au(III) with the shortest PONPE chain (n = 3) was also observed.

One-carbon metabolizing enzyme ALDH1L1 influences mitochondrial metabolism through 5-aminoimidazole-4-carboxamide ribonucleotide accumulation and serine depletion, contributing to tumor suppression.

Tumor cells generally require large amounts of nucleotides, and thus activate de novo purine synthesis (dnPS). In the dnPS reactions, 10-formyltetrahydorofolate (10-fTHF) supplied by one-carbon metabolism is utilized as a formyl group donor. We focused on aldehyde dehydrogenase 1 family member L1 (ALDH1L1), which metabolizes 10-fTHF to tetrahydrofolate and whose expression is often attenuated in hepatocellular carcinoma (HCC). We generated ALDH1L1-expressing HuH-7 cells to perform metabolome analysis and found that intracellular levels of serine were reduced and glycine was increased. In addition, 5-aminoimidazole-4-carboxamide ribonucleotide (ZMP), a dnPS intermediate, accumulated due to the consumption of 10-fTHF by ALDH1L1, which inhibited ZMP formylation. Importantly, ALDH1L1-expressing cells showed reduced ZMP sensitivity and higher mitochondrial activity. The suppression of mitochondrial serine catabolism by ALDH1L1 expression was speculated to be closely related to this phenotype. Gene set enrichment analysis utilizing The Cancer Genome Atlas data revealed that genes related to oxidative phosphorylation were enriched in HCC patients with high ALDH1L1 expression. Moreover, drug sensitivity data analysis demonstrated that HCC cell lines with low expression of ALDH1L1 were sensitive to ZMP and cordycepin, a structural analog of ZMP and AMP. Our study revealed that ZMP and AMP analogs might be effective in the pharmacotherapy of HCC patients with low expression of ALDH1L1.

Difference in fine specificity to polysaccharides of Candida albicans mannoprotein between mouse SIGNR1 and human DC-SIGN.

C-type lectin SIGNR1 directly recognizes Candida albicans and zymosan and has been considered to share properties of polysaccharide recognition with human DC-SIGN (hDC-SIGN). However, the precise specificity of SIGNR1 and the difference from that of hDC-SIGN remain to be elucidated. We prepared soluble forms of SIGNR1 and hDC-SIGN and conducted experiments to examine their respective specificities. Soluble SIGNR1 (sSIGNR1) bound several types of live C. albicans clinical isolate strains in an EDTA-sensitive manner. Inhibition analyses of sSIGNR1 binding by glycans from various yeast strains demonstrated that SIGNR1 preferentially recognizes N-glycan α-mannose side chains in Candida mannoproteins, as reported in hDC-SIGN. Unlike shDC-SIGN, however, sSIGNR1 recognized not only Saccharomyces cerevisiae, but also C. albicans J-1012 glycan, even after α-mannosidase treatment that leaves only ß1,2-mannose-capped α-mannose side chains. In addition, glycomicroarray analyses showed that sSIGNR1 binds mannans from C. albicans and S. cerevisiae but does not recognize Lewis(a/b/x/y) antigen polysaccharides as in shDC-SIGN. Consistent with these results, RAW264.7 cells expressing hDC-SIGN in which the carbohydrate recognition domain (CRD) was replaced with that of SIGNR1 (RAW-chimera) produced comparable amounts of interleukin 10 (IL-10) in response to glycans from C. albicans and S. cerevisiae, but those expressing hDC-SIGN produced less IL-10 in response to S. cerevisiae than C. albicans. Furthermore, RAW-hDC-SIGN cells remarkably reduced IL-10 production after α-mannosidase treatment compared with RAW-chimera cells. These results indicate that SIGNR1 recognizes C. albicans/yeast through a specificity partly distinct from that of its homologue hDC-SIGN.

Gender difference in subjective response to whole-body vibration under standing posture.

PURPOSE: The aim of this study was to examine whether there exist gender differences in subjective response to whole-body vibration (WBV) under standing posture. METHODS: Totally twenty-four participants (twelve males and twelve females) rated the discomfort of the test stimuli. The test stimuli included fore-and-aft (x), lateral (y), and vertical (z) vibration of three intensity levels (0.2, 0.4, and 0.8 m/s(2) r.m.s., unweighted), each of which had a constant power spectrum density at frequencies ranging from 1.0 to 20 Hz. The order of the test stimuli was fully randomized, and each stimulus was repeated three times. Subjective scale for discomfort caused by whole-body vibration exposure was obtained for each direction by using the category judgment method. Also, the mean Stevens' power law exponent was obtained for females and males at each vibration direction. RESULTS: The power exponents for females were significantly higher than those for males under fore-and-aft and lateral WBV exposure. Subjective discomfort scales obtained under fore-and-aft and lateral vibration exposure exhibited significant gender differences: the upper limits of categories up to "4: uncomfortable" for females were observed to be higher than those for males while the upper limits of category "5: very uncomfortable" for females were lower than those for males. In contrast, no significant gender differences were observed in the subjective discomfort scale or in the power law exponent for vertical WBV exposure. CONCLUSIONS: Our results suggest that females are subjectively more sensitive than males for fore-and-aft and lateral WBV exposure, especially at higher vibration magnitude. Therefore, the differential effects in subjective responses to WBV in females and males should be taken into account in the ISO standard currently used in discomfort evaluation.

Immunochemistry of pathogenic yeast, Candida species, focusing on mannan.

This review describes recent findings based on structural and immunochemical analyses of the cell wall mannan of Candida albicans, and other medically important Candida species. Mannan has been shown to consist of α-1,2-, α-1,3-, α-1,6-, and ß-1,2-linked mannopyranose units with few phosphate groups. Each Candida species has a unique mannan structure biosynthesized by sequential collaboration between species-specific mannosyltransferases. In particular, the ß-1,2-linked mannose units have been shown to comprise a characteristic oligomannosyl side chain that is strongly antigenic. For these pathogenic Candida species, cell-surface mannan was also found to participate in the adhesion to the epithelial cells, recognition by innate immune receptors and development of pathogenicity. Therefore, clarification of the precise chemical structure of Candida mannan is indispensable for understanding the mechanism of pathogenicity, and for development of new antifungal drugs and immunotherapeutic procedures.

A real-time gas monitoring system based on ion mobility spectrometry for workplace environmental measurements.

A volatile organic compounds (VOC) gas monitor was developed using an ion mobility spectrometer (IMS). It was designed for real-time monitoring in work environments, where gas chromatography/mass spectrometry (GC/MS) does not perform well. To evaluate the identification capability, response time, and quantitative accuracy of this device, experiments were conducted using methyl ethyl ketone. This is widely used in many factories, and its short-term exposure limit (STEL) has been set by the American Conference of Governmental Industrial Hygienists. Because the ionizable amount of methyl ethyl ketone has already been exceeded in STEL value of 300 ppm which belongs to the measurement range of interest in this study, this study estimated the peak shift amount rather than the peak intensity. Calibration curves with high accuracy were obtained in a range including 300 ppm which is the STEL of methyl ethyl ketone. The results of the experiment suggest that the device can be used for monitoring chemical substances in a work environment.

Chemical structure of beta-galactofuranose-containing polysaccharide and O-linked oligosaccharides obtained from the cell wall of pathogenic dematiaceous fungus Fonsecaea pedrosoi.

Fonsecaea pedrosoi is the main etiologic agent of chromoblastomycosis, usually occurring in tropical and subtropical areas. The cell wall components of pathogenic microorganisms behave as an antigen and/or ligand of the innate immune response. The cells of F. pedrosoi reacted with the α-galactopyranose-binding lectin (Griffonia simplicifolia lectin 1B4 isolectin, GSL 1B4), as well as the α-mannose-binding lectin, concanavalin A. The cell wall glycoprotein was isolated from conidial cells of F. pedrosoi, and its structure was analyzed by (1)H-nuclear magnetic resonance (NMR) and (13)C-NMR experiments. The N-linked polysaccharide moiety consists of a backbone ß-1,6-linked galactofuranose and α-1,6-linked mannose polymers, both of which are substituted with α-1,2-linked glucose side-chains. Furthermore, the glycoprotein contained a large amount of O-linked oligosaccharides, especially a hexaose that constituted approximately 20% of the glycoprotein. Unexpectedly, the hexaose had a highly branched structure which consisted of galactofuranose, galactopyranose, glucose and mannose residues as follows: An anti-F. pedrosoi antibody specifically reacted with the cells of F. pedrosoi, whereas other fungal cells that contain galactofuranose residues did not react. The reactivity of the antibody was strongly inhibited by the branched hexaose, suggesting that the characteristic structure of the O-linked hexaose involves the antigenic specificity of the cells.

Kinetics and solvent-dependent thermodynamics of water capture by a fullerene-based hydrophobic nanocavity.

Kinetic and thermodynamic properties of water encapsulation from organic solution by an open-cage [60]fullerene derivative have been investigated. 2D exchange NMR spectroscopy (EXSY) measurements were employed to determine the association and dissociation constants at 300-330 K (k(a) = 4.3 M(-1) × s(-1) and k(d) = 0.42 s(-1) at 300 K) in 1,1,2,2-tetrachloroethane-d(2) as well as the activation energies (E(a,ass) = 27 kJ mol(-1), E(a,diss) = 50 kJ mol(-1)). The equilibrium constants and thermodynamic parameters in various solvents (benzene-d(6), 1,2-dichlorobenzene-d(4), and dimethylsulfoxide-d(6)) were estimated using 1D-(1)H NMR spectroscopy. The parameters were dependent on the polarity of the solvent; ΔH depended linearly on the solvent polarity, becoming increasingly unfavorable as polarity increased. Mixtures of polar dimethylsulfoxide-d(6) in less polar 1,1,2,2-tetrachloroethane-d(2) showed a similar trend.

Adsorptive Removal of Heavy Metal Ions, Organic Dyes, and Pharmaceuticals by DNA-Chitosan Hydrogels.

DNA-chitosan (DNA-CS) hydrogel was prepared by in situ complexation between oppositely charged DNA and chitosan polyelectrolytes via electrostatic cross-linking to study its adsorption characteristics. The DNA-chitosan hydrogel matrix contains (i) cationic (NH3+) and anionic (PO4-) sites for electrostatic binding with ionic species, (ii) -OH and -NH2 groups and heteroaromatic DNA nucleobases for chelation of heavy metal ions, and (iii) DNA double-helix for recognition and binding to small organic molecules of various structures and polarities. DNA-CS hydrogels efficiently bind with Hg2+, Pb2+, Cd2+, and Cu2+ metal cations of significant environmental concern. Adsorption capacities of DNA-CS hydrogels for studied metal ions depend on hydrogel composition and pH of solution and reach ca. 50 mg/g at neutral pHs. Hydrogels with higher DNA contents show better adsorption characteristics and notably higher adsorption capacity to Hg2+ ions. Because of the co-existence of cationic and anionic macromolecules in the DNA-CS hydrogel, it demonstrates an affinity to both anionic (Congo Red) and cationic (Methylene Blue) dyes with moderate adsorption capacities of 12.6 mg/g and 29.0 mg/g, respectively. DNA-CS hydrogel can also be used for adsorptive removal of pharmaceuticals on conditions that their molecules are sufficiently hydrophobic and have ionogenic group(s). Facile preparation and multitarget adsorption characteristics of DNA-CS hydrogel coupled with sustainable and environmentally friendly characteristics render this system promising for environmental cleaning applications.

Cell wall N-glycan of Candida albicans ameliorates early hyper- and late hypo-immunoreactivity in sepsis.

Severe infection often causes a septic cytokine storm followed by immune exhaustion/paralysis. Not surprisingly, many pathogens are equipped with various anti-inflammatory mechanisms. Such mechanisms might be leveraged clinically to control septic cytokine storms. Here we show that N-glycan from pathogenic C. albicans ameliorates mouse sepsis through immunosuppressive cytokine IL-10. In a sepsis model using lipopolysaccharide (LPS), injection of the N-glycan upregulated serum IL-10, and suppressed pro-inflammatory IL-1ß, TNF-α and IFN-γ. The N-glycan also improved the survival of mice challenged by LPS. Analyses of structurally defined N-glycans from several yeast strains revealed that the mannose core is key to the upregulation of IL-10. Knocking out the C-type lectin Dectin-2 abrogated the N-glycan-mediated IL-10 augmentation. Furthermore, C. albicans N-glycan ameliorated immune exhaustion/immune paralysis after acute inflammation. Our results suggest a strategy where the immunosuppressive mechanism of one pathogen can be applied to attenuate a severe inflammation/cytokine storm caused by another pathogen.

Crystallization of the plant hormone receptors PYL9/RCAR1, PYL5/RCAR8 and PYR1/RCAR11 in the presence of (+)-abscisic acid.

Abscisic acid (ABA) is a plant hormone that plays key regulatory roles in physiological pathways for the adaptation of vegetative tissues to abiotic stresses such as water stress in addition to events pertaining to plant growth and development. The Arabidopsis ABA receptor proteins PYR/PYLs/RCARs form a START family that contains 14 members which are classified into three subfamilies (I-III). Here, purification, crystallization and X-ray data collection are reported for a member of each of the subfamilies, PYL9/RCAR1 from subfamily I, PYL5/RCAR8 from subfamily II and PYR1/RCAR11 from subfamily III, in the presence of (+)-abscisic acid. The three proteins crystallize in space groups P3(1)21/P3(2)21, P2 and P1, respectively. X-ray intensity data were collected to 1.9-2.6 A resolution.

Enzymatic synthesis of new oligosaccharides using mannosyltransferases from Candida species and their NMR assignments.

The outer layer of the cell wall of pathogenic fungi, Candida species, consists of mannan, which plays an important role in infection. In this study, we synthesized several oligosaccharides using mannosyltransferases obtained from Candida parapsilosis and Candida albicans. Namely, we synthesized mannotetraoses [Manalpha1--> 2Manalpha1-->3Manalpha1-->2Man and Manalpha1-->3(Manalpha1-->6)Manalpha1-->2Man] from mannotriose, Manalpha1-->3Manalpha1--> 2Man, and mannohexaoses [Manalpha1-->2Manalpha1-->3Manalpha1-->3Manalpha1-->2Manalpha1-->2Man and Manalpha1-->3(Manalpha1-->6)Manalpha1-->3Manalpha1-->2Manalpha1-->2Man] from mannopentaose, Manalpha1-->3Manalpha1-->3Manalpha1-->2Manalpha1-->2Man. The linkage sequence of these oligosaccharides was identified by a sequential (1)H-NMR assignment method combined with rotating frame nuclear Overhauser enhancement spectroscopy and relayed coherence transfer spectroscopy. The steric effect by the alpha-1,6-linked branching mannose residue to the H-1 proton chemical shift of the neighboring 3-O-substituted mannose residue was different from that of the 2-O-substituted mannose residue. These oligosaccharides having novel structures seem to be useful as the substrate or ligand for glycomics.

Conformational analysis of ß-1,2-linked mannobiose to mannoheptaose, specific antigen of pathogenic yeast Candida albicans.

Candida albicans contains characteristic ß-1,2-linked oligomannosyl moieties in the cell wall mannan. Reduction of the reducing termini of these oligosaccharides by NaBH(4) causes a significant downfield shift in the NMR signals for the second and third mannose units and upfield shift of the fourth mannose unit. To show the correlation between the shift in the NMR signals and the conformations of the ß-1,2-linked mannooligosaccharides, we performed molecular mechanics calculations. Six energy minima of the ß-1,2-linked mannobiose were found in the relaxed map computed using the AMBER force field. Five of the six energy minima could also be generated by a simulated annealing from a 900 K molecular dynamics. Similarly, the solution conformation of the ß-1,2-linked mannotriose to mannoheptaose was identified by the high temperature-simulated annealing. In the mannotetraose, the nonreducing terminal mannose unit was located near the reducing terminal one and formed a folded conformation. This result suggests that a mannose unit affects the H-1 chemical shifts of not only the second mannose unit, but also the third and fourth mannose units.

Author Correction: Identification of Two Mannosyltransferases Contributing to Biosynthesis of the Fungal-type Galactomannan α-Core-Mannan Structure in Aspergillus fumigatus.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.