Philip A.J. Gorin

Carbon-13 Nuclear Magnetic Resonance Spectroscopy of Polysaccharides

Publisher Summary This chapter examines the carbon-13 nuclear magnetic resonance spectroscopy of polysaccharides. The C-1 resonances of the pyranoid forms of glucose, xylose, galactose, arabinose, methyl glucoside, and methyl xyloside are shown to be sensitive to the anomeric configuration. The C-1 chemical-shifts of furanosides are generally at lower field than those of their anomeric counterparts in the pyranose series. The values of a series of α- and β-shifts have been determined for mono- O -methylglucoses and mono- O -methylmannoses to aid in the assignments of 13 C signals of oligosaccharides and polysaccharides consisting of glucose and mannose respectively. The 13 C-NMR spectra of polysaccharides having mixed linkages can sometimes be interpreted by the reference to the spectra of homopolymers representing each type of linkage. The C-2 to C-6 signals of monorhamnomannan were rationalized by gauging substitution-shifts and by the use of D -glucose precursors labeled with 2 H or 13 C. Glucose gave a rhamnomannan whose spectrum lacked the signal at 66.7, characterizing it as from C-6. The polysaccharides containing 3-deoxy- D -manno-octulosylonic acid residues are also elaborated.

Structural Chemistry of Fungal Polysaccharides

Publisher Summary This chapter discusses the structural chemistry of the polysaccharides and glycoproteins of fungal origin. The organisms considered are of the phylum Eumycophyta; this includes the classes Phycomycetes, Ascomycetes, Basidiomycetes, and Deuteromycetes. The Myxomyceteae include the slime molds, which are not generally recognized to be true fungi, having an amebic assimilative stage. The feature of fungal polysaccharides that is most striking to the chemist is that relatively few of them are structurally similar to polysaccharides from other natural sources. Structural knowledge of fungal polymers can be of aid in such fields as taxonomy, immunochemistry, biosynthesis of polysaccharides, and enzymolysis of polysaccharides. In the commercial area, polysaccharides that form viscous solutions have many potential uses, especially as plant–gum substitutes.

Polysaccharides of the lichens Cetraria islandica and Ramalina usnea

Abstract Cetraria islandica (Iceland moss) and Ramalina usnea, lichens having a fruticose-growth form and ascomycetous mycosymbionts, contain d -galacto- d -mannans with structures differing from any previously recognized. The polysaccharides are related, having (1→6)-linked α- d -mannopyranosyl main-chains. However, the C. islandica polysaccharide is more highly branched with α- d -Galp-(1→2)- and β- d -Galp-(1→4) side-chains linked to the same α- d -mannopyranosyl residues as in the preponderant structure {→6)-[α- d -Galp-(1→2)]-[β- d -Galp-(1→4)]-α- d -Manp-(1→6)-α- d -Manp-(1→}. The R. usnea d -galacto- d -mannan contains β- d -Galp-(1→4)-linked groups. R. usnea does not contain a β- d -glucan-resembling lichenan but has an α- d -glucopyranan preponderant repeating structure with three consecutive (1→3) links interspersed with single (1→4) links.

Assignment of signals of the carbon-13 magnetic resonance spectrum of a selected polysaccharide: Comments on methodology

Abstract The mannan from Rhodotorula glutinis contains alternate (1→3)- and (1→4)- linked β- D -mannopyranose residues ( 1 ) and its carbon-13 magnetic resonance spectrum displays 12 signals. These were assigned in terms of the positions of their parent nuclei in the sugar rings [but not whether the signals arose from a (1→3)- or (1→4)-linked residue] by preparation of D -mannans from specifically deuterated D -glucoses and observation of α- and β-deuterium isotope-effects. Individual assignments could then be made for carbon atoms of each unit by using the spectra of known oligo- and polysaccharides. The signal displacements of certain 13 C nuclei observed on O -methylation were compared with those obtained on O -mannosylation in order to determine whether methyl ethers could be used as model compounds for signal assignments in spectra of mannose-containing polysaccharides. The displacements observed were in the same direction and of a similar order of magnitude. An assessment is made of the use of the various techniques in assigning signals of polysaccharides and their possible interpretation in terms of chemical structure.

Chemical structure of the d-galacto-d-mannan component from hyphae of Aspergillus niger and other Aspergillus spp☆

Abstract The polysaccharides obtained by alkaline extraction of hyphae of Aspergillus niger 2022 contain d -mannosyl, d -galactosyl, and d --glucosyl units, the proportion of d -galactose decreasing and that of d -mannose increasing with age of culture. The polysaccharide of 5-day cultures contains d -gaIacto- d -mannans with a range of chemical structures, Fehling, precipitation providing polysaccharides of sugar composition which varied from one preparation to the other. This step removed most of the α- d -glucan present and analysis of the d -galacto- d -mannan-rich polysaccharide showed it to contain a core with a main chain of (1→6)-Iinked α- d -mannopyranosyl units substituted in the 2-position with side chains of α- d -mannopyranosyl, O -α- d -mannopyranosyl-(1→2)- O -α- d -mannopyranosyl, and O -α- d -mannopyranosyl-(1→2)- O -α- d -mannopyranosyl-(1→2)- O -α- d -mannopyranosyl units. The methylation and 13 C-n.m.r. data indicated side chains of (1→5)-Iinked β- d -galactofuranosyl residues having an average length of ∼4 units and linked to the mannan core at OH-6.Polysaccharides of Aspergillus fumigatus , Aspergillus terreus , Aspergillus flavus , and Aspergillus nidulans , prepared by alkaline extraction of hyphae, and precipitated by Cetavlon in the presence of borate have interrelated chemical structures.

Structural Chemistry of Polysaccharides from Fungi and Lichens

Publisher Summary This chapter discusses the chemical structures of the polysaccharides of fungi and lichens investigated from 1967 to the middle of 1980. It is convenient to group the polysaccharides in terms of their chemical structures, according to the nature of the component sugars, the predominant linkage and configuration, and, in the case of heteropolymers, the nature of the main chain. The cell walls of Fusicoccum amygdali are stained blue with iodine and attacked by alpha amylase. Extracts of Sporothrix schenckii and Ceratocystis stenoceras contain 4-O-substituted D -glucopyranosyl units and the solutions give a blue color with iodine. Glycogens have been isolated from Candida albicans, Blastocladiella emersonii, Neurospora crassa, Allomyces macrogynus, Rhizophydium sphaerotheca, and Monoblepharella elongata. They have β-amylolysis values of 45–45% and average chain-length (x) values of 11–14 D -glucosyl units. This chapter briefly discusses about glucans including pseudonigeran, pullulan, cellulose etc; mannans including linear mannans etc; galactans; and heteropolysaccharides based on D-mannan main-chains and galactan main-chains.

Cell constituents of mycelia and conidia of Aspergillus fumigatus

Abstract Cell-wall components of mycelia and conidia of Aspergillus fumigatus contain alkali-soluble polysaccharides comprised of d -galacto- d -mannans which coprecipitated with small proportions of a d -glucan, tentatively identified as glycogen. The fine structures of the d -galacto- d -mannans varied as a function of the cell type. In a 5-day-old mycelium, the polysaccharide consisted of a main chain of (1→6)-linked α- d -mannopyranose residues substituted at O-2 by 1 to 3 α- d -mannopyranosyl units that are (1→2)-interlinked. β- d -Galactofuranosyl units are (1→6)-linked to the d -mannan core, being components of side-chains of average length of ∼6 units, which are (1→5)-interlinked. The 10-day-old mycelium had a similar d -galacto- d -mannan, but the proportion of glycogen was smaller. Conidia contain polysaccharides of different structure, as shown by the 13C-n.m.r. spectrum and by methylation analysis. Side chains composed of a single unit of β- d -galactofuranosyl linked (1→6) to adjacent d -mannopyranosyl units were identified with a minor proportion of 6-O-substituted d -galactofuranosyl units. Also present were nonreducing d -galacto-pyranosyl end-groups and 2-amino-2-deoxyglycosyl units. The glucan component was not glycogen. Conidial walls have much less protein than mycelial walls. Predominant amino acids in the latter were aspartic and glutamic acids, tyrosine, alanine, and glycine. Fatty acids C16, C18, C18:1, and C18:2 were present in the mycelial and conidial walls, C18:2 was present in minor amounts in the mycelial wall, but was a major component of the lipid fraction from whole cells.

TORULOPSIS BOMBICOLA SP. N.

A new yeast species,Torulopsis bombicola, is described, that produces extracellular hydroxy fatty acid sophorosides. It utilizes relatively few carbon compounds. It forms a mannan having a proton magnetic resonance spectrum similar to the spectra of the galactomannans ofTorulopsis apis, Torulopsis nodaensis andT. magnoliae, but differing from those ofT. gropengiesseri galactomannan andT. apicola mannan.

Properties of 13C-N.M.R. spectra of O-(1-carboxyethylidene) derivatives of methyl β-d-galactopyranoside: models for determination of pyruvic acid acetal structures in polysaccharides

Abstract 13 C-N.m.r. spectra were recorded of compounds containing O -(1-carboxyethylidene) groups linked to galactopyranose and fucopyranose derivatives. These compounds are useful as aids in determination of the positions and configurations of pyruvic acid acetal substituents in polysaccharides. Chemical shifts of non-protonated acetal carbons depend on whether the acetal ring is 5-membered (δ c 107–109.5) or 6-membered (δ c 100.5–102.4). The C-3 signals of 3,4-(1-carboxyethylidene) acetals are typical, being at ∼δ c 81 and in the case of the barium salt of the methyl β- d -galactopyranoside derivative. The exact value depends on the configuration, whether it is as in 6 (δ c 81.1) or 5 (δ c 80.4). The CH 3 signals of proton-n.m.r. spectra are also diagnostically useful, falling at δ 1.97 and 2.07 respectively. (The foregoing shift-values are pH-dependent). The pyruvylated galactan from the snail, Pomacea lineata , was shown to contain some residues that could be assigned a structure corresponding, in the positions of acetal substitution and acetal configuration, to structure 6 . Compound 6 (barium salt) is of interest as its 13 C-n.m.r. spectrum lacks non-protonated carbonyl and acetal carbon resonances, when obtained by the usual procedures. While this is principally because of long T 1 values, the non-protonated acetal carbon signals are comparatively broad, possibly through slow conformational interchange. In the case of the carbonyl resonance, the lack of sensitivity is because of a low n.O.e. value of 1.4, approximately one half that of other carbon atoms in the molecule.

Enzymic degradation of yeast cell-wall mannans and Galactomannans to polymeric fragments containing α-(1→6)-linked D-mannopyranose residues

Abstract The cell-wall D -mannans of Candida parapsilosis, Endomycopsis fibuliger, Saccharomyces rouxii, Torulopsis apicola (Hajsig strain), and Torulopsis bombi were degraded with an exo α- D -mannosidase from Arthrobacter GJM-1 to their α-(1→6)-linked D -mannopyranose main-chains, as demonstrated by p.m.r. spectroscopy. D -galacto- D -mannans from Candida lipolytica, Torulopsis gropengiesseri, Torulopsis lactis-condensi, Torulopsis magnoliae, and Trichosporon fermentans could be degraded to polysaccharides containing mainly 6- O -linked α- D -mannopyranosyl residues following preferential removal of their enzyme-resistant, D -galactopyranosyl non-reducing end-units with acid. The D -mannans of Saccharomyces lodderi, Citeromyces matritensis , and Pichia pastoris could also be enzymically degraded to polysaccharides containing predominantly α-(1→6)-linked D -mannopyranosyl residues after hydrolysis of most of the β- D -linked residues in their side chains with acid. The exo α- D -mannosidase, as would be expected, produced β- D -mannose on splitting of an α-(1→2)-linked D -mannopyranose tetramer. It is, however, very selective in its action since it did not cleave α- D -Man p -(1→2)-β- D -Man p -(1→2)-β- D -Man p -(1→2)-β- D -Man p -(1→2)- D -Man. Apparently a D -mannopyranose non-reducing end-unit and two consecutive α- D -mannopyranose residues are required by the enzyme for cleavage of a substrate to take place.