Fred R. Seymour

Structural analysis of dextrans, from strains of leuconostoc and related genera, that contain 3-O-α-d-glucosylated α-d-glucopyranosyl residues at the branch points, or in consecutive, linear positions

Abstract Dextran fractions from NRRL strains Leuconostoc mesenteroides B-523, B-742, B-1149, Betabacterium vermiforme B-1139, and Streptococcus viridans B-1351 were examined by 13 C-n.m.r. spectroscopy. The native, structurally homogeneous dextrans from NRRL strains of L. mesenteroides B-1191, B-1192, and B-1142 were also examined by 13 C-n.m.r. spectroscopy, and the spin-lattice relaxation values of dextran B-1142 were measured. Methylation-fragmentation, structural analyses were performed on dextrans B-1142 and B-1191. Except for the A fractions of dextrans B-523 and B- 1149, all of these dextran fractions differ from linear dextran by branching primarily, if not exclusively, through 3,6-di- O -substituted α- d -glucopyranosyl residues. Dextran B-1149 fraction A is spectroscopically different from the dextrans branching through the 3,6-di- O -substituted residues, and apparently contains significant mole percentages of contiguously linked 3-mono- O -substituted α- d -glucopyranosyl residues.

Methylation structural analysis of unusual dextrans by combined gas-liquid chromatography-mass spectrometry☆

Abstract Eight bacterial dextrans from NRRL strainsLeuconostoc mesenteroides B-742, B-1299, B-1355, B-1399, and B-1402, and from Streptobacterium dextranicum B-1254 were examined by methylation structural analysis. Methyl ethers of d -glucose that were present in hydrolyzates of permethylated dextrans were analyzed by combined g.l.c.−m.s. as the peracetylated aldononitriles. The various dextrans differed significantly in frequency and type of chain branching.

High-temperature enhancement of 13C-N.M.R. chemical-shifts of unusual dextrans, and correlation with methylation structural analysis

Abstract Dextran fractions from NRRL strains Leuconostoc mesenteroides B-742, B-1299, B-1355, and Streptobacterium dextranicum B-1254 were examined by 13 C-n.m.r. spectroscopy at 34 and 90°, and by methylation structural analysis. The native, structurally homogeneous dextran from L. mesenteroides NRRL B-1402 was also examined. The data allow correlations to be made between the structure and physical properties of the S (soluble) and L (less-soluble) fraction pairs of dextrans B-742, B-1254, B-1299, and B-1355. For the dextrans under consideration here, increasing solubility of the dextran (both in water and in aqueous ethanol) was found to correlate with decreasing percentages of α- d -(1→6)-linked d -glucopyranosyl residues. Both the diagnostic nature of the 70–75-p.p.m. spectral region with regard to type of dextran branching, and the increase in resolution of the polysaccharide spectra at higher temperatures, have been further confirmed.

13C-nuclear magnetic resonance spectra of compounds containing β-D-fructofuranosyl groups or residues

Abstract 13 C-N.m.r. spectra have been recorded for sucrose, melezitose, levan, inulin, palatinose, and D -fructose. Except for the last, each compound contains a different O -substituted D -fructofuranose residue or group, or β- D -fructofuranosyl residue or group. On the basis of chemical-shift displacements, resulting from O -substitution at specific carbon atoms, resonances can be assigned to the carbon atoms of the β- D -fructofuranosyl residue. Fortuitously, the α- D -glucopyranosyl group present in some of these compounds exhibits resonances that do not obscure the β- D -fructofuranosyl resonances. O -Substitution of the β- D -fructofuranosyl residue causes a downfield displacement of the corresponding, linked-C resonance; however, the other major resonances of this residue are not affected by bulky substituents. Members of a series of levan fractions, the products of partial, acid hydrolysis of Streptoccoccus salivarius levan, were then examined for changes in relative degree of branching.

Correlation of the structure of dextrans to their 1H-n.m.r. Spectra

Abstract Dextran fractions from NRRL strains Leuconostoc mesenteroides B-742, B-1299, B-1355, and B-1501, Streptobacterium dextranicum B-1254, Streptococcus sp. B-1526, and also the native dextrans from L. mesenteroides B-1142, B-1191, B-1402, and L. dextranicum B-1420 were examined in aqueous solution at 90° by Fourier-transform, 1H-n.m.r. spectroscopy. Branching of dextrans through the 2,6-, 3,6-, and 4,6-di-O-substituted α- d -glucopyranosyl residues was correlated to changes in spectral patterns. The major, spectral differences for these dextrans were in the anomeric (4-6-p.p.m.) region. In general, the degree of branching of a dextran can be determined by comparing anomeric-peak integrals; however, the integrals of the displaced, nonlinear, anomeric resonances are also dependent on the type of branching residues present in the dextran. Although the 1H-n.m.r. resonances for the anomeric region identify the presence of non-6-mono-O-substituted α- d -glucopyranosyl residues, these additional resonances provide little discrimination between other residue types, the exception being the 2,6-di-O-substituted residue, which has a clearly displaced resonance. Techniques for the suppression of the interfering resonance of deuterium hydroxide are also discussed.

Identification Of aldoses by use of their peracetylated aldononitrile derivatives: A G.L.C-M.S. approach☆

Abstract The g.l.c. retention-times and detector responses have been examined for peracetylated aldononitrile derivatives from aldoses. Correlations have been made between changes in g.l.c. retention-times and changes in the stereochemistry and functional groups of the parent aldose. The mass spectra [electron impact (e.i.), ammonia chemical ionization (c.i.), and methane c.i.] for these g.l.c. peaks were recorded. C.i.-mass spectrometry (m.s.) indicated the molecular weights of the derivatives, and the number of aldehyde and alcohol groups in the parent aldose. E.i.-m.s. indicated the nature and position of functional groups present in the parent aldose. Aldoses containing acetamido, amino, deoxy, and thio substituents were studied.

The α-d-glucopyranosidic linkages of dextrans: comparison of percentages from structural analysis by periodate oxidation and by methylation

Abstract The analyses of 25 dextrans by g.l.c.-m.s., methylation-fragmentation, and periodate-oxidation techniques have been compared. Although in general agreement for slightly branched dextrans, the two techniques yield divergent analyses for highly branched dextrans. Employing the methylation-fragmentation data as the standard, the periodate-oxidation data were examined to establish the extent of deviation for the types of α- d -glucopyranosidic linkages that occur in dextrans, that is, the (1→6)-like, the (1→4)-like, and the (1→3)-like. The unexpected behavior of the dextrans was correlated with whether branching occurs through either C-2 or C-4, or C-3 or both of these types. Possible causes for the effects observed are discussed.

Structural analysis of α-d-glucans by 13C-nuclear magnetic resonance, spin-lattice relaxation studies

Abstract Relaxation measurements have been made for the resonances of the 13 C-n.m.r. spectra of the S fractions of dextrans from NRRL strains Leuconostoc mesenteroides B-742, B-1299, B-1355, and B-1498, the S[L] fraction of the dextran from Streptobacterium dextranicum B-1254, pullulan, and a synthetically branched, comb-like amylose. Resonance assignments have been made to carbon-atom positions on the basis that carbon atoms associated with large degrees of segmental motion will have resonances with larger than average dipole-dipole spin-lattice relaxation ( T 1 DD ) values. For a given spectrum, the relative magnitude of T 1 DD values are about the same as the observed spin-lattice relaxation ( T 1 obs ) values for each resonance. Comparisons of the relative magnitudes of relaxation data are most easily made with the resonances of anomeric positions. In general, the relative magnitude of the relaxation values for the spectrum of a given compound did not change between 34° and 90° recording conditions. Relaxation measurements were employed to establish the relative position of O -substituted residues in the average repeating unit of the S fractions of dextrans B-1355 and B-1498. The general parameters controlling the magnitudes of the chemical shifts of the α- d -glucopyranosyl residue were then considered in relation to the nature of the O -substitution for this residue.

Structural analysis of insoluble d-glucans by fourier-transform, infrared difference-spectrometry: correlation between structures of dextrans from strains of leuconostoc mesenteroides and of d-glucans from strains of streptococcus mutans

Abstract Fourier-transform infrared (F.t.-i.r.) difference-spectra have been recorded, relative to a water-soluble dextran of low degree of branching, for (a) dextrans from Leuconostoc mesenteroides NRRL B-742 (the L fraction) and NRRL B-1149 (the A fraction), (b) d -glucans from Streptococcus mutans KR-1 and OMA 176, and (c) the controls of amylose, cellulose, nigeran, and pseudonigeran. Confirmation has been obtained for the presence, in the spectra of the relatively insoluble dextrans and d -glucans, of a previously recognized, characteristic absorbance at 822 cm−1, and the correlation of this band with contiguous, linearly (1 → 3)-linked, α- d -glucopyranosyl residues, to which polymer insolubility (and cariogenic properties) has been ascribed. This analytical method allows the mole percent of the contiguously linked 3-mono-O-substituted α- d -glucopyranosyl residues to be quickly and non-destructively established in solid-state samples, when employing weights of polysaccharides in the microgram range. The wavenumbers and intensities of other bands observed in the F.t.-i.r. difference-spectra of d -glucans containing (1→4)- d -linkages are also discussed.

Fourier-transform, infrared difference-spectrometry for structural analysis of dextrans

Abstract The Fourier-transform (F.t.), infrared (i.r.) spectra of a series of branched dextrans were examined. The dextrans studied were those from the N R R L collection designated Leuconostoc mesenteroides B-1142, B-1191, B-1299 fraction S, B-1355 fraction S, B-1402, and B-1422, and Streptobacterium dextranicum B-1254 fractions S[L] and L[S]. The spectrum of a levan, N R R L L. mesenteroides B-523 fraction M, was also examined, for comparison with the spectra of the dextrans. Meaningful results were obtained by “weight-normalizing” the spectral absorbance to that of the dextran of very low degree of branching (dextran B-1254 fraction L[S]), and then subtracting this spectrum of linear dextran from each of the other polysaccharide spectra. The resulting i.r.-absorbance difference-spectra were plotted, at uniform scale-expansion across the 1800-400-cm −1 region, resulting in difference-absorbance features at ≈ 1100 and ≈ 800 cm −1 for all branched dextrans. These absorbance differences could be correlated to the type and degree of dextran branching, which had previously been established by permethylation analysis. It was concluded that such F.t.-i.r. difference-spectra have general application for the structural analysis of polysaccharides.