| 1. |
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| 2. |
- Jacobs, Anna, Ph. D., et al.
(författare)
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Characterization of water-soluble hemicelluloses from spruce and aspen employing SEC/MALDI mass spectroscopy
- 2002
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Ingår i: Carbohydrate Research. - 1873-426X .- 0008-6215. ; 337:8, s. 711-717
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Tidskriftsartikel (refereegranskat)abstract
- Partly depolymerized hemicelluloses isolated from wood chips of spruce and aspen employing microwave treatment were resolved using size-exclusion chromatography (SEC) into oligo- and polysaccharide fractions containing components with a narrow range of sizes, as determined by MALDI mass spectroscopy. The degree of substitution with acetyl moieties (DS) was also calculated on the basis of the MALDI-MS spectra obtained prior to and following deacetylation. For spruce hemicelluloses, the low molecular mass fraction contained small arabino-4-O-methylglucuronoxylan oligosaccharides, with DP values ranging from 4 to ~20, separated primarily on the basis of their charge density. The fraction eluted last consisted of an O-acetyl-(galacto)glucomannan polysaccharide of peak-average DP value (DPp) 14. The degree of substitution with acetyl groups (DS) decreased with decreasing DP, a value DS of 0.39 being obtained for the fraction with DPp 12. For the aspen hemicelluloses, the SEC fractions eluted first contained an acidic O-acetyl-4-O-methylglucuronoxylan polysaccharide with DP ranging from 10 to ~28 and an average DS of ~0.75. The fractions eluted last consisted of oligosaccharide mixtures composed primarily of small neutral O-acetyl-xylooligosaccharides (DPp 6, DS 0.41), together with minor quantities of an O-acetyl-glucomannan.
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| 3. |
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| 4. |
- Kihlberg, Jan, et al.
(författare)
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Synthetic receptor analogues: preparation and calculated conformations of the 2-deoxy, 6-O-methyl, 6-deoxy, and 6-deoxy-6-fluoro derivatives of methyl 4-O-α-D-galactopyranosyl-β-D-galactopyranoside (methyl β-D-galabioside)
- 1988
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Ingår i: Carbohydrate Research. - : Elsevier BV. - 1873-426X .- 0008-6215. ; 176:2, s. 271-286
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Tidskriftsartikel (refereegranskat)abstract
- The 2-deoxy (7), 6-O-methyl (15), 6-deoxy (22), and 6-deoxy-6-fluoro (31) derivatives of methyl β-d-galabioside (1) have been synthesised. Thus, 7 was prepared by xanthate reduction using tributyltin hydride, whereas 22 was obtained by catalytic hydrogenation of a 6-deoxy-6-iodogalabioside. Regioselective mono-fluorination of methyl 2,3-di-O-benzoyl-β-d-galactopyranoside with Et2NSF3 and subsequent α-d-galactosylation provided 31. Molecular mechanics calculations yielded similar conformations for 1, 7, 15, 22, and 31 with differes in φH and ψH of 5°. No indications of intramolecular hydrogen bonds, as displayed by 1 in the crystal, were found for 7, 15, 22, or 31.
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| 5. |
- Micova, Julia, et al.
(författare)
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Characterisation and X-ray crystallography of products from the Bucherer-Bergs reaction of methyl 2,3-O-isopropylidene-α-D-lyxo-pentodialdo-1,4-furanoside
- 2003
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Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 338:19, s. 1917-1924
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Tidskriftsartikel (refereegranskat)abstract
- Methyl 2,3-O-isopropylidene-α-D-mannofuranosidurononitrile [alternative name: methyl (5R)-5-C-cyano-2,3-O-isopropylidene-α-D-lyxofuranoside] (2), methyl 2,3-O-isopropylidene-α-D-mannofuranosiduronamide [methyl (5S)-5-C-carbamoyl-2,3-O-isopropylidene-α-D-lyxofuranoside; methyl (5S)-2,3-O-isopropylidene-α-D-lyxo-hexofuranosiduronamide] (3), methyl 2,3-O-isopropylidene-α-D-mannofuranosiduronic acid [methyl (5S)-2,3-O-isopropylidene-α-D-lyxo-hexofuranosiduronic acid] (4), methyl 5-deoxy-2,3-O-isopropylidene-5-ureido-β-L-gulofuranosiduronamide [methyl (5R)-5-deoxy-2,3-O-isopropylidene-5-ureido-α-D-lyxo-hexofuranosiduronamide (5), and (4S,5S,6R)-5,6-dihydro-6-hydroxy-4,5-isopropylidenedioxy-4H-pyrido[2,1-e]imidazolidine-2',4'-dione [IUPAC name: (3aS,4R,8aS)-4-hydroxy-2,2-dimethyl-3a,8a-dihydro-4H-1,3-dioxa-4a,6-diaza-s-indacene-5,7-dione] (6), instead of the expected hydantoin derivative, were obtained from the Bucherer-Bergs reaction of methyl 2,3-O-isopropylidene-α-D-lyxo-pentodialdo-1,4-furanoside (1). The structure of 6 was deduced from NMR and mass spectral data and confirmed by X-ray crystallography. The configuration at C-5 in 2-5 was confirmed by establishing the 5S configuration of 3 by X-ray crystallography. Conformations of the six- and five-membered rings in 3 and 6 are also discussed.
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| 6. |
- Sabharwal, Hemant, et al.
(författare)
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Oligosaccharides from faeces of a blood-group B, breast-fed infant
- 1988
-
Ingår i: Carbohydrate Research. - : Elsevier BV. - 1873-426X .- 0008-6215. ; 178:1, s. 145-154
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Tidskriftsartikel (refereegranskat)abstract
- Eight oligosaccharides have been isolated from faeces of a blood group B, secretor, breast-fed infant and characterized by sugar and methylation analysis, f.a.b. mass spectrometry and 1H-n.m.r. spectroscopy. One of these oligosaccharides has not previously been reported and is a tri-L-fucosyl derivative of lacto-N-hexaose. The other compounds were identical to oligosaccharides found in human milk. Several of the reported compounds require the secretor dependent 2'-fucosyltransferase for their biosynthesis. Since the mother of this child was an O(H) non-secretor, an intestinal biosynthesis of at least some of these compounds is strongly indicated. No blood group B active oligosaccharides were detected which is in sharp contrast to the oligosaccharide excretion in faeces from a blood group A infant [Sabharwal et al., Mol. Immunol., 21 (1984) 1105-1112] in which all the major oligosaccharides isolated were blood group A active.
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| 7. |
- Steiner, Bohumil, et al.
(författare)
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Some non-anomerically C-C-linked carbohydrate amino acids related to leucine - synthesis and structure determination
- 2003
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Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 338:13, s. 1349-1357
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Tidskriftsartikel (refereegranskat)abstract
- (5'R)-5'-Isobutyl-5'-[methyl (4R)-2,3-O-isopropylidene-β-L-erythrofuranosid-4-C-yl]-imidazolidin-2',4'-dione was synthesised starting from methyl 2,3-O-isopropylidene-α-D-lyxo-pentodialdo-1,4-furanoside via methyl 6-deoxy-6-isopropyl-2,3-O-isopropylidene-α-D-lyxo-hexofuranosid-5-ulose applying the Bucherer-Bergs reaction. Its 5'-R configuration was confirmed by X-ray crystallography. Corresponding α-amino acid-methyl (5R)-5-amino-5-C-carboxy-5,6-dideoxy-6-isopropyl-α-D-lyxo-hexofuranoside (alternative name: 2-[methyl (4R)-β-L-erythrofuranosid-4-C-yl]-D-leucine) was obtained from the above hydantoin by acid hydrolysis of the isopropylidene group followed by basic hydrolysis of the hydantoin ring. Analogous derivatives with 5S configuration, formed in a minority, were also isolated and characterised.
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| 8. |
- Bauer, S H J, et al.
(författare)
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A rapid and sensitive procedure for determination of 5-N-acetyl neuraminic acid in lipopolysaccharides of Haemophilus influenzae : a survey of 24 non-typeable H-influenzae strains
- 2001
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Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 335:4, s. 251-260
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Tidskriftsartikel (refereegranskat)abstract
- In view of the importance of 5-N-acetyl neuraminic acid in bacterial pathogenesis, a sensitive, reproducible and reliable method for the determination of 5-N-acetyl neuraminic acid levels in lipopolysaccharide (LPS) is described and applied to 24 different non-typeable Haemophilus influenzae (NTHi) strains. The method involves analysis by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) of terminal 5-N-acetyl neuraminic acid residues released by neuraminidase treatment of O-deacylated LPS. The procedure is relatively fast and the instrumental effort is moderate. The results of the procedure were compared with data obtained by H-1 NMR and electrospray ionisation-mass spectrometry (ESI-MS). The analysis of LPS from 24 NTHi strains showed that 5-N-acetyl neuraminic acid was found to be a common constituent of LPS in NTHi. Only one strain (NTHi 432) did not show any sialylation. Molar ratios (LPS /5-N-acetyl neuraminic acid) ranged between 5/1 and 500/1. Several strains in which no 5-N-acetyl neuraminic acid could be determined by other methods including 1H NMR and ESI-MS were shown to contain 5-N-acetyl neuraminic acid by this HPAEC-PAD procedure. The method was applied to determine levels of terminal 5-N-acetyl neuraminic acid in LPS from NTHi strains grown under different conditions and mutant strains containing inactive LPS biosynthetic genes.
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| 9. |
- Bennett, Neil A., et al.
(författare)
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Biochemical and catalytic properties of an endoxylanase purified from the culture filtrate of Thermomyces lanuginosus ATCC 46882
- 1998
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Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 306:3, s. 445-455
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Tidskriftsartikel (refereegranskat)abstract
- An endoxylanase (1,4-beta-D-xylan xylanohydrolase, EC 3.2.1.8) from the culture filtrates of T. lanuginosus ATCC 46882 was purified to homogeneity by DEAE-Sepharose and Bio-Gel P-30 column chromatographies. The purified endoxylanase had a specific activity of 888.8 mumol min-1 mg-1 protein and accounted for approximately 30% of the total protein secreted by this fungus. The molecular mass of native (non-denatured) and denatured endoxylanase were 26.3 and 25.7 kD as, respectively. Endoxylanase had a pI of 3.7 and was optimally active between pH 6.0-6.5 and at 75 degrees C. The enzyme showed > 50% of its original activity between pH 5.5-9.0 and at 85 degrees C. The pH and temperature stability studies revealed that this endoxylanase was almost completely stable between pH 5.0-9.0 and up to 60 degrees C for 5 h and at pH 10.0 up to 55 degrees C for 5 h. Thin-layer chromatography (TLC) analysis showed that endoxylanase released mainly xylose (Xyl) and xylobiose (Xyl2) from beechwood 4-O-methyl-D-glucuronoxylan, O-acetyl-4-O-methyl-D-glucuronoxylan and rhodymenan (a beta-(1-->3)-beta(1-->4)-xylan). Also, the enzyme released an acidic xylo-oligosaccharide from 4-O-methyl-D-glucuronoxylan, and an isomeric xylotetraose and an isomeric xylopentaose from rhodymenan. The enzyme hydrolysed [1-3H]-xylo-oligosaccharides in an endofashion, but the hydrolysis of [1-3H]-xylotriose appeared to proceed via transglycosylation. since the xylobiose was the predominant product. Endoxylanase was not active on pNPX and pNPC at 40 and 100 mM for up to 6 h, but showed some activity toward pNPX at 100 mM after 20-24 h. The results suggested that the endoxylanase from T. lanuginosus belongs to family 11.
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| 10. |
- Borriss, R., et al.
(författare)
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Enzymatic synthesis of 4-methylumbelliferyl (1 -> 3)-beta-D-glucooligosaccharides - new substrates for beta-1,3-1,4-D-glucanase
- 2003
-
Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 338:14, s. 1455-1467
-
Tidskriftsartikel (refereegranskat)abstract
- The transglycosylation reactions catalyzed by beta-1,3-D-glucanases (laminaranases) were used to synthesize a number of 4-methylumbelliferyl (MeUmb) (1 --> 3)-beta-D-gluco-oligosaccharides having the common structure [beta-D-Glcp-(1 --> 3)](n)-beta-D-Glcp-MeUmb, where n = 1-5. The beta-1,3-D-glucanases used were purified from the culture liquid of Oerskovia sp. and from a homogenate of the marine mollusc Spisula sachalinensis. Laminaran and curdlan were used as (1 --> 3)-beta-D-glucan donor substrates, while MeUmb-beta-D-glucoside (MeUmbGlcp) was employed as a transglycosylation acceptor. Modification of [beta-D-Glcp-(1 --> 3)](2)-beta-D-Glcp-MeUmb (MeUmbG(3)) gives 4,6-O-benzylidene-D-glucopyranosyl or 4,6-O-ethylidene-D-glucopyranosyl groups at the non-reducing end of artificial oligosaccharides. The structures of all oligosaccharides obtained were solved by H-1 and C-13 NMR spectroscopy and electrospray tandem mass spectrometry. The synthetic oligosaccharides were shown to be substrates for a beta-1,3-1,4-D-glucanase from Rhodothermus marinus, which releases MeUmb from beta-di- and beta-triglucosides and from acetal-protected beta-triglucosides. When acting upon substrates with d.p. > 3, the enzyme exhibits an endolytic activity, primarily cleaving off MeUrnbGlcP and MeUmbG(2).
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| 11. |
- Christakopoulos, Paul, et al.
(författare)
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Enhancement of pH-stability of a low molecular mass endoglucanase from Fusarium oxysporum by protein pegylation
- 1998
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Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 314:1-2, s. 95-99
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Tidskriftsartikel (refereegranskat)abstract
- The stability of the low molecular mass endoglucanase (23.2 kDa) from Fusarium oxysporum at alkaline pH was enhanced by chemical modification. Two distinct types of amino acid-specific modifiers were used. The first, either cyanuric chloride activated polyethylene glycol (CC–PEG) or polyethylene glycol succinimidyl succinate active ester (SS–PEG), react (more or less specifically) with protein amino groups. The second type, maleimide polyethylene glycol (Mal–PEG), is specific for cysteinyl residues. The enzyme lost almost all of its activity when modified with CC–PEG, whereas no inactivation was observed with SS–PEG and Mal–PEG. The modified endoglucanase showed remarkably enhanced alkaline pH stability. When acting upon cello-oligosaccharides and 4-methylumbelliferyl cello-oligosaccharides, the enzyme preferentially cleaved the internal glycosidic bonds. The modified enzymes mediated a decrease in the viscosity of carboxymethyl cellulose (CMC) associated with the release of only small amounts of reducing sugar. Thus, the modified enzyme retains the endo character of the native enzyme
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| 12. |
- Christakopoulos, Paul, et al.
(författare)
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Purification and characterisation of a major xylanase with cellulase and transferase activities from Fusarium oxysporum
- 1996
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Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 289, s. 91-104
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Tidskriftsartikel (refereegranskat)abstract
- A major xylanase from Fusarium oxysporum was purified to homogeneity by gel filtration, affinity, and ion-exchange chromatographies. It has a molecular mass of 60.2 kDa and pl of 6.6 and was optimally active at pH 7.4 and at 50 °C. The enzyme was stable over the pH range 5.8–8.2 at 40 °C for 24 h and lost 45% of its original activity at pH 9.0 under the identical conditions. The enzyme rapidly hydrolysed xylans from oat spelts (husks) and birchwood, but the activities on carboxymethylcellulose (CMC), filter paper, and Avicel were very low. Determination of kcat/Km revealed that the enzyme hydrolysed oat spelts and birchwood xylans, 15–30 times more efficiently than CMC. In a 24 h incubation, at pH 7.0 and 9.0, the enzyme hydrolysed oat spelts and birchwood xylans by 75 and 65%, respectively. However, at pH 7.0, the enzyme released almost equal amounts of xylose and xylobiose from both xylans, whereas at pH 9.0, the concentration of xylobiose was twice as muchi as that of xylose and xylotriose. Xylanase attacked preferentially the internal glycosidic bonds of xylo- and 4-methylumbelliferyl cello-oligosaccharides [MeUmb(Glc)n]. The enzyme catalysed transglycosylation reaction with xylotriose, xylotetraose, and xylopentaose as donors and 4-methylumbelliferyl β-d-glucoside (MeUmbGlc) as an acceptor.
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| 13. |
- Christakopoulos, Paul, et al.
(författare)
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The alkaline xylanase III from Fusarium oxysporum F3 belongs to family F/10
- 1997
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Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 302:3-4, s. 191-195
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Tidskriftsartikel (refereegranskat)abstract
- Xylanase III from Fusarium oxysporum F3 was purified to homogeneity by ion-exchange chromatography and gel filtration. The enzyme has a molecular mass of 38 kDa, an isoelectric point of 9.5, and is maximally active on oat spelt xylan at pH 7 and 45 °C with a Km of 0.8 mg/mL. The xylanase displays remarkable stability at pH 9.0. It is not active on xylotriose but hydrolyzes the 4-methylumbelliferyl glycosides of β-xylobiose and --- , and to a lower extent 4-methylumbelliferyl β-cellobioside. When acted on xylooligosaccharides and xylan, analysis of reaction mixtures by high-pressure liquid chromatography shows preferred internal glycoside cleavage. Thus the purified enzyme appears to be a true endo-β-1,4-xylanase. Partial amino acid analysis of xylanase III shows high sequence homology with xylanases of family F/10.Xylanase III from Fusarium oxysporum F3 was purified to homogeneity by ion-exchange chromatography and gel filtration, and was functionally characterised. The enzyme displays remarkable stability at pH 9.0, appears to be a true endo-β-1,4-xylanase, and shows high sequence homology with xylanases of family F/10.
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| 14. |
- Eneyskaya, E. V., et al.
(författare)
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Enzymatic synthesis of beta-xylanase substrates : transglycosylation reactions of the beta-xylosidase from Aspergillus sp
- 2003
-
Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 338:4, s. 313-325
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Tidskriftsartikel (refereegranskat)abstract
- A beta-D-xylosidase with molecular mass of 250 +/- 5 kDa consisting of two identical subunits was purified to homogeneity from a cultural filtrate of Aspergillus sp. The enzyme manifested high transglycosylation activity in transxylosylation with p-nitrophenyl P-D-xylopyranoside (PNP-X) as substrate, resulting in regio- and stereoselective synthesis of p-nitrophenyl (PNP) beta-(1 --> 4)-D-xylooligosaccharides with dp 2-7. All transfer products were isolated from the reaction mixtures by HPLC and their structures established by electrospray mass spectrometry and H-1 and C-13 NMR spectroscopy. The glycosides synthesised, beta-Xyl-1 --> (4-beta-Xyl-1 -->)(n)4-beta-Xyl-OC6H4NO2-p (n = 1 - 5), were tested as chromogenic substrates for family 10 beta-xylanase from Aspergillus orizae (XynA) and family 11 beta-xylanase I from Trichoderma reesei (XynT) by reversed-phase HPLC and UV-spectroscopy techniques. The action pattern of XynA against the foregoing PNP beta-(1 --> 4)-D-xylooligosaccharides differed from that of XynT in that the latter released PNP mainly from short PNP xylosides (dp 2 - 3) while the former liberated PNP from the entire set of substrates synthesised.
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| 15. |
- Garegg, P.J., et al.
(författare)
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Transglucosidation of methyl and ethyl D-glucopyranosides by alcoholysis
- 2002
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Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 337:6, s. 517-521
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Tidskriftsartikel (refereegranskat)abstract
- The transglucosidations of methyl 4-O-methyl-a- and -ß-D-glucopyranoside in ethanolic camphor-10-sulfonic acid, and of ethyl 4-O-methyl-a- and -ß-D-glucopyranoside in methanolic camphor-10-sulfonic acid, have been studied. Samples were removed at intervals and the proportions of the glucosides determined by GC of their acetates. The results show that the anomer with the inverted configuration predominates in the initially formed product (˜59-70%). This indicates that all the studied reactions proceed via the same mechanism, involving exocyclic C-O cleavage and formation of a glucopyranosylium ion, but that the eliminated alcohol exerts some steric hindrance, which favors the approach of the other alcohol from the opposite side. © 2002 Published by Elsevier Science Ltd.
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| 16. |
- Gellerstedt, Göran, et al.
(författare)
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An HPLC method for the quantitative determination of hexeneuronic acid groups in chemical pulps
- 1996
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Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 294, s. 41-51
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Tidskriftsartikel (refereegranskat)abstract
- It has recently been demonstrated that 4-deoxy-L-threo-hex-4-enopyranosyluronic acid (''hexeneuronic acid'') is present in kraft pulps and linked to the xylan backbone. An analytical method for the quantitative determination of hexeneuronic acid groups has now been developed. The procedure involves a selective hydrolysis with mercuric acetate of the glucosidic linkage between the hexeneuronic acid group and the xylan chain, followed by oxidation with periodate to form P-formyl pyruvic acid. The latter is reacted with thiobarbituric acid, and the red-coloured adduct formed is separated by reverse phase HPLC and quantified by measuring the absorbance at 549 nm, Some kraft pulps have been analysed to illustrate the contribution of hexeneuronic acid groups to the total amount of oxidizable structures present in such pulps.
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| 17. |
- Gulin, Sofia, et al.
(författare)
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Structural studies of S-7, another exocellular polysaccharide containing 2-deoxy-arabino-hexuronic acid
- 2001
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Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 331:3, s. 285-290
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Tidskriftsartikel (refereegranskat)abstract
- The exocellular polysaccharide S-7, a heteropolysaccharide from Azotobacter indicus var, myxogenes has been studied using methylation analysis, Smith degradation, partial acid hydrolysis, NMR spectroscopy and mass spectrometry as the principal methods. It is concluded that the repeating unit has the following structure: -->4)-beta -D-Glcp-(1 -->4)-alpha -L-Rhap-(1 -->3)-beta -D-2-deoxy-arabino-HexpA-(1 --> 6 up arrow 1 beta -D-Glcp-(1 -->6)-beta -D-Glcp The absolute configuration of the deoxyhexuronic acid was deduced from H-1 NMR chemical shifts and is most likely D. Approximately two O-acetyl groups per repeating unit are present, one of which is presumably on the Rha residue. The structure bears great resemblance to another polysaccharide, recently studied, produced by Sphingomonas paucimobilis I-886.
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| 18. |
- Johansson, K.-J., et al.
(författare)
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Transglucosidation of methyl and ethyl D-glucofuranosides by alcoholysis
- 2001
-
Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 332:1, s. 33-39
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Tidskriftsartikel (refereegranskat)abstract
- The acid catalyzed ethanolysis of methyl 5-O-methyl-a- and -ß-D-glucofuranoside and the analogous methanolysis of ethyl 5-O-methyl-a- and -ß-D-glucofuranoside have been investigated. For all four reactions, the primarily formed transglycosylation product was a single glycoside that had the opposite anomeric configuration to the starting material. This strongly indicates that a D-glucose methyl ethyl acetal is first formed and is then ring closed by a nucleophilic attack by HO-4, giving either the starting material or a transglycosylation product with the opposite anomeric configuration. Low percentages of the methyl ethyl acetals and of dimethyl acetals were also observed in the reaction product during the methanolysis reactions. © 2001 Elsevier Science Ltd.
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| 19. |
- Katapodis, Petros, et al.
(författare)
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Biochemical and catalytic properties of an endoxylanase purified from the culture filtrate of Sporotrichum thermophile
- 2003
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Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 338:18, s. 1881-1890
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Tidskriftsartikel (refereegranskat)abstract
- An endo-β-1,4-xylanase (1,4-β-d-xylan xylanoxydrolase, EC 3.2.1.8) present in culture filtrates of Sporotrichum thermophile ATCC 34628 was purified to homogeneity by Q-Sepharose and Sephacryl S-200 column chromatographies. The enzyme has a molecular mass of 25,000 Da, an isoelectric point of 6.7, and is optimally active at pH 5 and at 70 °C. Thin-layer chromatography (TLC) analysis showed that endo-xylanase liberates mainly xylose (Xyl) and xylobiose (Xyl2) from beechwood 4-O-methyl-d-glucuronoxylan, O-acetyl-4-O-methylglucuronoxylan and rhodymenan (a β-(1→4)-β(1→3)-xylan). Also, the enzyme releases an acidic xylo-oligosaccharide from 4-O-methyl-d-glucuronoxylan, and an isomeric xylotetraose and an isomeric xylopentaose from rhodymenan. Analysis of reaction mixtures by high performance liquid chromatography (HPLC) revealed that the enzyme cleaves preferentially the internal glycosidic bonds of xylooligosaccharides, [1-3H]-xylooligosaccharides and xylan. The enzyme also hydrolyses the 4-methylumbelliferyl glycosides of β-xylobiose and β-xylotriose at the second glycosidic bond adjacent to the aglycon. The endoxylanase is not active on pNPX and pNPC. The enzyme mediates a decrease in the viscosity of xylan associated with a release of only small amounts of reducing sugar. The enzyme is irreversibly inhibited by series of ω-epoxyalkyl glycosides of d-xylopyranose. The results suggest that the endoxylanase from S. thermophile has catalytic properties similar to the enzymes belonging to family 11.
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| 20. |
- Lahmann, Martina, Docent i kemi, 1963-, et al.
(författare)
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A facile approach to diosgenin and furostan type saponins bearing a 3 beta-chacotriose moiety
- 2002
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Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 337:21-23, s. 2153-2159
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Tidskriftsartikel (refereegranskat)abstract
- Combination of a one-pot coupling technique and the use of benzyl ethers as permanent protecting groups offered a short and simple route to dioscin-type saponins. This strategy in combination with a mild reductive opening procedure of the spiroketal function in diosgenin also offered a convenient approach to bidesmosidic furostan type saponins. (Me3NBH3)-B-./AlCl3 promoted acetal opening of 3-O-TBDMS-protected diosgenin gave the 26-OH acceptor 9 into which a benzylated beta-glucose moiety was introduced by a S(N)2-type imidate coupling. After cleavage of the silyl ether, the 3beta-O-glucose and the 4-O-linked rhamnose of the chacotriose unit were introduced by a NIS/AgOTf-promoted one-pot coupling sequence utilising thioglycoside donors and their different reactivity in different solvents. After removal of a benzoyl group, the same coupling conditions were also used for the coupling of the second 2-O-linked rhamnose unit. The target substance was obtained after cleavage of the protecting benzyl ethers under Birch-type conditions, which did not affect the double bond in the steroid skeleton.
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| 21. |
- Lahmann, Martina, Docent i kemi, 1963-, et al.
(författare)
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Synthesis of alpha-tocopheryl oligosaccharides
- 1997
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Ingår i: Carbohydrate Research. - UNIV HAMBURG,INST ORGAN CHEM,D-20146 HAMBURG,GERMANY. : Elsevier BV. - 0008-6215 .- 1873-426X. ; 299:1-2, s. 23-31
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Tidskriftsartikel (refereegranskat)abstract
- As effective natural antioxidants, tocopherols and also their esters are frequently added to foodstuffs, pharmaceuticals and cosmetics. For increase of polarity, hence solubility in water, a series of alpha-tocopheryl oligosaccharides was synthesised using BF3-etherate. The pure alpha-tocopheryl beta-maltotetraoside as well as the higher homologues proved to be water-soluble.
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| 22. |
- Li, Jiebing, et al.
(författare)
-
The contribution to kappa number from hexeneuronic acid groups in pulp xylan
- 1997
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Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 302:3-4, s. 213-218
-
Tidskriftsartikel (refereegranskat)abstract
- The kappa number of chemical pulps is widely used both in mill operation and in laboratory work as a measure of the degree of delignification in pulping, oxygen delignification, and prebleaching. Recently, it has been shown that the kappa number reflects not only lignin but also carbohydrate structures sensitive to oxidation by permanganate, notably hexeneuronic acid groups linked to xylan. In the present work, the kappa number units originating from hexeneuronic acid groups calculated on a molar basis have been determined in two different ways, viz. by permanganate oxidation of model compounds and by selective elimination of hexeneuronic acid groups from a series of kraft pulps. The results are in good agreement with each other and demonstrate that 10 mu mol of hexeneuronic acid correspond to 0.84-0.86 kappa units. From kappa number determinations combined with hydrolysis of the pulp with mercuric acetate, it is possible to calculate the amount of hexeneuronic acid groups present in a pulp.
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| 23. |
- Schweda, Elke K H, et al.
(författare)
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Structural analysis of lipopolysaccharide oligosaccharide epitopes expressed by non-typeable Haemophilus influenzae strain 176
- 2002
-
Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 337:5, s. 409-420
-
Tidskriftsartikel (refereegranskat)abstract
- The structure of the lipopolysaccharide (LPS) from non-typeable Haemophilus influenzae strain 176 has been investigated. Electrospray ionization-mass spectrometry (ESIMS) on O-deacylated LPS (LPS-OH) and core oligosaccharide (OS) samples obtained after mild-acid hydrolysis of LPS provided information on the composition and relative abundance of the glycoforms. ESIMS tandem-mass spectrometry on LPS-OH confirmed the presence of minor sialylated and disialylated glycoforms. Oligosaccharide samples were studied in detail using high-field NMR techniques. It was found that the LPS contains the common inner-core element of H. influenzae. L-alpha-D-Hepp-(1-->2)-[PEtn-->6]-L-alpha-D-Hepp-(1-->3)-[beta-D-Glep-(1 -->4)]-L-alpha-D-Hepp-(1-->5)[PPEtn-->4]-alpha-Kdop-(2-->6)-Lipid A having glycosyl substitution at the O-3 position of the terminal heptose as recently observed for non-typeable H. influenzae strain 486 [Mansson, M.: Bauer. S. H. J.: Hood, D. W.; Richards, J. C. Moxon, E. R. Schweda. E. K. H., Eur. J. Biochem. 2001. 268. 2148-2159]. The following LPS structures were identified as the major glycoforms. the most significant being indicated with an asterisk (*) (glycoforms are partly substituted with Gly at the terminal Hep): [GRAPHICS].
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| 24. |
- Schweda, Elke K H, et al.
(författare)
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Structural profiling of lipopolysaccharide glycoforms expressed by non-typeable Haemophilus influenzae : phenotypic similarities between NTHi strain 162 and the genome strain Rd
- 2003
-
Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 338:23, s. 2731-2744
-
Tidskriftsartikel (refereegranskat)abstract
- Non-typeable Haemophihis influenzae (NTHi) is a significant cause of otitis media in children. We have employed single and multiple step electrospray ionization mass spectrometry (ESIMS) and NMR spectroscopy to profile and elucidate lipopolysaccharide (LPS) structural types expressed by NTHi strain 162, a strain obtained from an epidemiological study in Finland. ESIMS on O-deacylated LPS (LPS-OH) and core oligosaccharide (OS) samples of LPS provided information on the composition and relative abundance of glycoforms differing in the number of hexoses linked to the conserved inner-core element, L-alpha-D-Hepp-(1--> 2)-[PEtn --> 6]-L-alpha-D-Hepp-(1 --> 3)-L-alpha-D-Hepp-(1 --> 5)(.)[PPEtn --> 4]-alpha-Kdop-(2 --> 6)-Lipid A of H. influenzae LPS. The strain examined was found to elaborate Hex2 to Hex5 LPS glycoform populations having structures identical to those observed for H. influenzae strain Rd [Risberg, A.; Masoud, H.; Martin, A.; Richards, J.C.; Moxon, E.R.; Schweda, E.K.H. Eur. J Biochem. 1999, 261, 171-180], the strain for which the complete genome has been sequenced. In addition, sialyllactose-containing glycoforms previously identified in strain Rd as well as several NTHi strains, were identified as minor components. Multiple step tandem ESIMS (MS") on dephosphorylated and permethylated OS provided information on the arrangement of glycoses within the major population of glycoforms and on the existence of additional isomeric glycoforms. Minor Hex1 and Hex6 glycoforms were detected and characterized where the Hex6 glycoform was comprised of a dihexosamine-containing pentasaccharide chain attached at the proximal heptose residue of the inner-core unit. LPS structural motifs present in the NTHi strain 162 are expressed by a genetically diverse set of disease causing isolates, providing the basis for a vaccine strategy against NTHi otitis media.
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| 25. |
- Teleman, Anita, et al.
(författare)
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Characterization of O-acetyl-(4-O-methylglucurono)xylan isolated from birch and beech
- 2002
-
Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 337:4, s. 373-377
-
Tidskriftsartikel (refereegranskat)abstract
- The structures of water-soluble birch and beech xylans, extracted from holocellulose using dimethyl sulfoxide, were determined employing 1H and 13C NMR spectroscopy together with chemical analysis. These polysaccharides were found to be O-acetyl-(4-O-methylglucurono)xylans containing one 4-O-methylglucuronic acid substituent for approximately every 15 D-xylose residues. The average degree of acetylation of the xylose residues in these polymers was 0.4. The presence of the structural element → 4)[4-O-Me-α-D-GlcpA-(1 → 2)][3-O-Ac]-β-D-Xylp-(1 → was demonstrated. Additional acetyl groups were present as substituents at C-2 and/or C-3 of the xylopyranosyl residues. Utilizing size-exclusion chromatography in combination with mass spectroscopy, the weight-average molar masses (and polydispersities) were shown to be 8000 (1.09) and 11,100 (1.08) for birch and beech xylan, respectively.
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| 26. |
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| 27. |
- Abrahamsson, Carl-Olof, et al.
(författare)
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Xylosylated naphthoic acid-amino acid conjugates for investigation of glycosaminoglycan priming.
- 2008
-
Ingår i: Carbohydrate Research. - : Elsevier BV. - 1873-426X .- 0008-6215. ; 343:9, s. 1473-1477
-
Tidskriftsartikel (refereegranskat)abstract
- Three different series of xylosylated naphthoic acid-amino acid conjugates containing one or two amino acid residues were synthesized for the investigation of glycosaminoglycan priming and potential use as anti-tumor drugs. All xylosylated naphthoic acid-conjugates inhibited the growth of normal lung fibroblasts to some extent, whereas the growth of tumor derived T24 carcinoma cells was not affected. There was no correlation between amino acid conjugation, retention time and the antiproliferative activity. Only one compound initiated the priming of glycosaminoglycans. Modification of the naphthalene ring with one or two amino acid residues did not have any effect on proteoglycan biosynthesis or glycosaminoglycan priming in T24 carcinoma cells.
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| 28. |
- Alexandersson, Elin, et al.
(författare)
-
Complete H-1 and C-13 NMR spectral assignment of D-glucofuranose
- 2022
-
Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 511
-
Tidskriftsartikel (refereegranskat)abstract
- Although D-glucose is the most common sugar in nature, only a few NMR studies have focused on its minor furanose forms, and they have been limited to the anomeric position. Here, complete H-1 and C-13 NMR spectral analysis of alpha- and beta-D-glucofuranose was performed, including signal assignment, chemical shifts, and coupling constants. Selective and non-selective 1D and 2D NMR experiments were used for the analysis, complemented by spin simulations and iterative spectral analysis.
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| 29. |
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| 30. |
- Amer, Adel, et al.
(författare)
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A regio- and stereo-controlled approach to triazoloquinoxalinyl C-nucleosides
- 2010
-
Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 345:17, s. 2474-2484
-
Tidskriftsartikel (refereegranskat)abstract
- The synthesis of a new series of acyclic triazoloquinoxalinyl C-nucleosides and their transformation to their cyclic analogs are described following protection, activation, and deprotection with subsequent intramolecular nucleophilic substitution protocol. The antibacterial potency of the new compounds was determined using an inhibition zone diameter test. The results show that 3a and 2b exhibit good activity against Escherichia coli and Candida albicans. On the other hand, the cyclic mesylated C-nucleoside 13 showed activity against the Gram-positive bacteria (Staphylococcus aureus) and antifungal activity against C. albicans.
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| 31. |
- Andersson, Rolf, et al.
(författare)
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Structural studies of the lipopolysaccharide of Moritella viscosa strain M2-226
- 2012
-
Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 347, s. 164-167
-
Tidskriftsartikel (refereegranskat)abstract
- The structure of the O-specific side chain of the lipopolysaccharide from the Gram-negative psychrophilic bacterium Moritella viscosa strain M2-226, responsible for the winter ulcer in Atlantic salmon, has been determined. Monosaccharide analysis and H-1 and C-13 NMR spectroscopy were employed to elucidate the structure. It was concluded that the polysaccharide is composed of a trisaccharide repeating unit with the following structure:)-> 3-beta-D-GlcpNAc-(1 -> 4)-[alpha-D-GlcpA-(1 -> 3)]-alpha-L-Fucp-(1 -> (C) 2011 Elsevier Ltd. All rights reserved.
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| 32. |
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| 33. |
- Araújo, Ana Catarina, et al.
(författare)
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A general route to xyloglucan-peptide conjugates for the activation of cellulose surfaces
- 2012
-
Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 354, s. 116-120
-
Tidskriftsartikel (refereegranskat)abstract
- Cellulose is an attractive supporting matrix for diverse biotechnological applications, including chromatography, diagnostics, and tissue replacement/scaffolding, due to its renewable resource status, low cost, and low non-specific interaction with biomolecules. In an effort to expand the biofunctionality of cellulose materials, we present here a versatile method for the synthesis of xyloglucan-peptide conjugates that harness the strong xyloglucan-cellulose binding interaction for gentle surface modification. Xylogluco-oligosaccharide aminoalditols (XGO-NH2) were coupled to both linear and cyclic peptides, which contained the endothelial cell epitope Arg-Gly-Asp, in a facile two-step approach employing diethyl squarate cross-linking. Subsequent xyloglucan endo-transglycosylase-mediated coupling of the resulting XGO-GRGDS (Gly-Arg-Gly-Asp-Ser) and XGO-c[RGDfK]-PEG-PEG (cyclo[Arg-Gly-Asp-(D-Phe)-Lys]-PEG-PEG; where PEG is 8-amino-3,6-dioxaoctanoic acid) conjugates into high molecular mass xyloglucan yielded xyloglucan-RGD peptide conjugates suitable for cellulose surface activation. Notably, use of XGO-squaramate as a readily accessible, versatile intermediate overcomes previous limitations of solid-phase synthetic approaches to XGO-peptide conjugates, and furthermore allows the method to be generalized to a wide variety of polypeptides and proteins, as well as diverse primary amino compounds.
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| 34. |
- Arewang, Carl Johan, et al.
(författare)
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Synthesis of urine drug metabolites : glucuronic acid glycosides of phenol intermediates
- 2007
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Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 342:7, s. 970-974
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Tidskriftsartikel (refereegranskat)abstract
- The investigation of drug metabolism requires substantial amount of metabolites. Isolation from urine is tedious, therefore, the material obtained by synthesis is preferred. Substantial amounts of three tentative drug metabolites, phenolic glucuronides, have been prepared using easily available glycosyl donors. The final products [3(2-N-methyl-N-isopropylaminoethoxy)phenyl] beta-D-glucopyranosiduronic acid, 4-amino-3,5-dimethylphenyl beta-D-glucopyranosiduronic acid and [2(S)-propanoyl-6-O-naphthyl] beta-D-glucopyranuronic acid are useful as, for example, reference material in metabolite investigations.
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| 35. |
- Avetyan, David L., et al.
(författare)
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Scalable total synthesis of natural vanillin-derived glucoside omega-esters
- 2022
-
Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 522, s. 108683-
-
Tidskriftsartikel (refereegranskat)abstract
- The first total synthesis of vanilloloside, calleryanin, and a series of naturally occurring omega-esters of vanilloloside was realized through direct glycosylation of vanillin-based aglycones or late-stage derivatization of vanilloloside. All aglycones and their fragments were synthesized from vanillin as the sole aromatic precursor. Subsequently, these intermediates were used to construct various vanillin-derived glucoside omega-esters using a mild acidic deacetylation as the key synthetic step, providing the final products in the total yields of 10-50% and general purity of >95%. Additionally, the first operationally simple and sustainable synthesis of litseafoloside B was realized on large scale, avoiding the use of toxic solvents and reagents, providing an attractive alternative to isolation of this and other similar compounds from plant sources.
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| 36. |
- Bergenstråhle, Malin, 1977-, et al.
(författare)
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Simulation studies of the insolubility of cellulose
- 2010
-
Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 345:14, s. 2060-2066
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Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics simulations have been used to calculate the potentials of mean force for separating short cellooligomers in aqueous solution as a means of estimating the contributions of hydrophobic stacking and hydrogen bonding to the insolubility of crystalline cellulose. A series of four potential of mean force (pmf) calculations for glucose, cellobiose, cellotriose, and cellotetraose in aqueous solution were performed for situations in which the molecules were initially placed with their hydrophobic faces stacked against one another, and another for the cases where the molecules were initially placed adjacent to one another in a co-planar, hydrogen-bonded arrangement, as they would be in cellulose ID. From these calculations, it was found that hydrophobic association does indeed favor a crystal-like structure over solution, as might be expected. Somewhat more surprisingly, hydrogen bonding also favored the crystal packing, possibly in part because of the high entropic cost for hydrating glucose hydroxyl groups, which significantly restricts the configurational freedom of the hydrogen-bonded waters. The crystal was also favored by the observation that there was no increase in chain configurational entropy upon dissolution, because the free chain adopts only one conformation, as previously observed, but against intuitive expectations, apparently due to the persistence of the intramolecular O3-O5 hydrogen bond.
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| 37. |
- Bergh, Anders, et al.
(författare)
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Carbohydrate functionalization using cationic iron carbonyl complexes
- 2008
-
Ingår i: Carbohydrate Research. - : Elsevier BV. - 1873-426X .- 0008-6215. ; 343:10-11, s. 1808-1813
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Tidskriftsartikel (refereegranskat)abstract
- Cationic iron carbonyl cyclohexadiene complexes were employed in the derivatization of the 3-OH position of unprotected and protected methyl beta-D-galactopyranosides using two different approaches, giving access to galactopyranosides with an aromatic or cyclohexadienoic functionality in this position. (c) 2008 Elsevier Ltd. All rights reserved.
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| 38. |
- Bertoft, Eric
(författare)
-
Fine structure characterization of amylopectins from grain amaranth starch
- 2009
-
Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 344, s. 1701-1708
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to determine the fine structure of amylopectin from grain amaranth. Amaranthus amylopectin was hydrolyzed with a-amylase, and single clusters and a group of clusters (domain) were isolated by methanol precipitation. The domain and the clusters were treated with phosphorylase a and then P-amylase to remove all external chains, whereby the internal structure was obtained. The phi,beta-limit dextrins were analyzed on Sepharose CL 6B. The average DP (degree of polymerization) and peak-DP values of fractions of clusters were 57 and 82, respectively; the values of the domain were 137 and 309, respectively. The unit chain length profiles were analyzed by high-performance anion-exchange chromatography with pulsed amperometric detector (HPAEC-PAD). The results showed that the domain fraction contained similar to 2.2 clusters, and single clusters were composed of similar to 13 chains. The phi,beta-limit dextrins of the clusters were further hydrolyzed with a-amylase to characterize their building block composition. The average DP of the branched blocks was similar to 11 and they contained on average similar to 2.5 chains. Their average chain length, internal chain length, and degree of branching were approximately 4.3, 2.8, and 14, respectively. A cluster consisted of similar to 6 branched blocks, and the internal chain length between the blocks was similar to 6.8. (C) 2009 Elsevier Ltd. All rights reserved.
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| 39. |
- Bertoft, Eric
(författare)
-
The molecular structure of waxy maize starch nanocrystals
- 2009
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Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 344, s. 1558-1566
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Tidskriftsartikel (refereegranskat)abstract
- The insoluble residues obtained by submitting amylopectin-rich native starch granules from waxy maize to a mild acid hydrolysis consist of polydisperse platelet nanocrystals that have retained the allomorphic type of the parent granules. The present investigation is a detailed characterization of their molecular composition. Two major groups of dextrins were found in the nanocrystals and were isolated. Each group was then structurally characterized using beta-amylase and debranching enzymes (isoamylase and pullulanase) in combination with anion-exchange chromatography. The chain lengths of the dextrins in both groups corresponded with the thickness of the crystalline lamellae in the starch granules. Only similar to 62 mol % of the group of smaller dextrins with an average degree of polymerization ((DP) over bar) 12.2 was linear, whereas the rest consisted of branched dextrins. The group of larger dextrins ((DP) over bar 31.7) apparently only consisted of branched dextrins, several of which were multiply branched molecules. It was shown that many of the branch linkages were resistant to the action of the debranching enzymes. The distribution of branched molecules in the two populations of dextrins suggested that the nanocrystals possessed a regular and principally homogeneous molecular structure. (C) 2009 Elsevier Ltd. All rights reserved.
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| 40. |
- Bidgoli, Hossein, et al.
(författare)
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Effect of carboxymethylation conditions on water binding capacity of chitosan-based superabsorbents
- 2010
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Ingår i: Carbohydrate Research. - : Elsevier - Pergamon. - 0008-6215 .- 1873-426X. ; 345:18, s. 2683-2689
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Tidskriftsartikel (refereegranskat)abstract
- A superabsorbent polymer (SAP) from chitosan was provided via carboxymethylation of chitosan, followed by cross-linking with glutaraldehyde and freeze-drying. This work was focused on an investigation of the effects of monochloroacetic acid (MCAA), sodium hydroxide, and reaction time on preparation of carboxymethylchitosan (CMCS). The CMCS products were characterized using FTIR spectroscopy, and their degrees of substitution (DS) were measured using conductimetry and FTIR analysis. The highest DS value was obtained when the carboxymethylation reaction was carried out using 1.75 g MCAA and 1.75 g NaOH per g of chitosan in 4 h. The water solubilities of the CMCS products at various pHs were also evaluated, and the results indicated a significant impact of the reaction parameters on the solubility of CMCS. The CMCSs with the highest DS value resulted in SAPs having the highest water-binding capacity (WBC). TheWBCof the best SAP measured after 10 minexposure in distilled water, 0.9% NaCl solution, synthetic urine, and artificial blood was 104, 33, 30, and 57 g/g, respectively. The WBC of this SAP at pH 2–9 passed a maximum at pH 6.
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| 41. |
- Borisova, Anna, et al.
(författare)
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alpha-Galactobiosyl units: thermodynamics and kinetics of their formation by transglycosylations catalysed by the GH36 alpha-galactosidase from Thermotoga maritima
- 2015
-
Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 401, s. 115-121
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Tidskriftsartikel (refereegranskat)abstract
- Broad regioselectivity of a-galactosidase from Thermotoga maritima (pTmGal36A) is a limiting factor for application of the enzyme in the directed synthesis of oligogalactosides. However, this property can be used as a convenient tool in studies of thermodynamics of a glycosidic bond. Here, a novel approach to energy difference estimation is suggested. Both transglycosylation and hydrolysis of three types of galactosidic linkages were investigated using total kinetics of formation and hydrolysis of pNP-galacto-biosides catalysed by monomeric glycoside hydrolase family 36 a-galactosidase from T. maritima, a retaining exo-acting glycoside hydrolase. We have estimated transition state free energy differences between the 1,2-and 1,3-linkage (Delta Delta G(0)(double dagger) values were equal 5.34 +/- 0.85 kJ/ mol) and between 1,6-linkage and 1,3-linkage (Delta Delta G(0)(double dagger) = 1.46 +/- 0.23 kJ/mol) in pNP-galactobiosides over the course of the reaction catalysed by TmGal36A. Using the free energy difference for formation and hydrolysis of glycosidic linkages (Delta Delta G(F)(double dagger) -Delta Delta G(H)(double dagger)), we found that the 1,2-linkage was 2.93 +/- 0.47 kJ/ mol higher in free energy than the 1,3-linkage, and the 1,6-linkage 4.44 +/- 0.71 kJ/ mol lower. (C) 2014 Elsevier Ltd. All rights reserved.
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| 42. |
- Borisova, Anna, et al.
(författare)
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The method of integrated kinetics and its applicability to the exo-glycosidase-catalyzed hydrolyses of p-nitrophenyl glycosides.
- 2015
-
Ingår i: Carbohydrate Research. - : Elsevier BV. - 1873-426X .- 0008-6215. ; 412, s. 43-49
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Tidskriftsartikel (refereegranskat)abstract
- In the present work we suggest an efficient method, using the whole time course of the reaction, whereby parameters kcat, Km and product KI for the hydrolysis of a p-nitrophenyl glycoside by an exo-acting glycoside hydrolase can be estimated in a single experiment. Its applicability was demonstrated for three retaining exo-glycoside hydrolases, β-xylosidase from Aspergillus awamori, β-galactosidase from Penicillium sp. and α-galactosidase from Thermotoga maritima (TmGalA). During the analysis of the reaction course catalyzed by the TmGalA enzyme we had observed that a non-enzymatic process, mutarotation of the liberated α-d-galactose, affected the reaction significantly.
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| 43. |
- Börjesson, Mikaela, 1987, et al.
(författare)
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Branching of hemicelluloses through an azetidinium salt ring-opening reaction
- 2016
-
Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 428, s. 23-30
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Tidskriftsartikel (refereegranskat)abstract
- During the last century there has been a steady increase in the number of publications on practical applications of hemicellulose. Due to the water and moisture sensitivity, poor film-forming ability and lack of thermal processability most of the hemicelluloses need to be chemically modified prior to processing into materials. Within this study we present the results of azetidinium salts as a new functional group for conjugation to polysaccharides. The reactivity of three azetidinium salts on xylan, arabinoxylan and galactoglucomannan was investigated. Carbonyl groups were found to be favorable for the reaction with azetidinium salts and thus the glucuronic acid content in the hemicellulose determines the degree of substitution. TEMPO-oxidation of the hemicelluloses was done which successfully increased the degree of substitution. The highly reactive azetidinium salts are easily synthesized from secondary amines and epichlorohydrin and can be used as a new tool toward functionalization of hemicelluloses into the after sought properties.
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| 44. |
- Cabero, Karen, et al.
(författare)
-
A cellulolytic Hypocrea strain isolated from South American brave straw produces a modular xylanase.
- 2012
-
Ingår i: Carbohydrate Research. - : Elsevier BV. - 1873-426X .- 0008-6215. ; 356, s. 215-223
-
Tidskriftsartikel (refereegranskat)abstract
- Cellulase-producing fungi from the Andean regions in Bolivia, an ecosystem characterized as an extreme arid highland, were studied. Thirty-two isolates were screened for presence of cellulase activity using carboxymethyl cellulose (CMC) as carbon source, and activity was confirmed using a filter paper assay. One isolate, denoted as BLT1C was selected from this screening, and sequence analysis of the internal transcribed spacer (ITS) classified the strain as Hypocrea lixii. The secretome of BLT1C showed high xylanase activity (compared to that of two reference Trichoderma reesei strains) when cultivated using brave straw, an abundant native grass from the area, as carbon source. SDS-PAGE analysis revealed three main protein-bands (18, 32 and 65kDa) and in-gel digestion and mass spectrometry combined with activity analysis showed that these proteins were active xylanases with molecular masses corresponding to (I) a single glycoside hydrolase family 11 catalytic module (18kDa), and (II, III) modular enzymes, with the GH11 catalytic domain connected to a module of unknown function (32kDa) or putatively connected to a GH7 catalytic module (65kDa). The N-terminal sequence of the 65kDa xylanase did not show significant sequence similarities to deposited sequences. The collected data on xylanase activity, molecular mass, GH11-sequence conservation, combined with lack of sequence similarities in the N-terminus show that the 65kDa band corresponds to a novel modular xylanase.
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| 45. |
- Cuers, Julia, et al.
(författare)
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Simultaneous determination of substituent patterns in partially acid hydrolyzed O-Me/O-Me-d(3)-cellulose and quantification of the obtained oligomers by HPLC-ESI-MS
- 2012
-
Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 348, s. 55-63
-
Tidskriftsartikel (refereegranskat)abstract
- Substituent patterns in oligosaccharide derivatives obtained from methyl cellulose were determined up to DP10 by electrospray ionization mass spectrometry employing separation of the oligomer fractions by HPLC. Oligosaccharides were labeled with meta-aminobenzoic acid after perdeuteromethylation and partial hydrolysis of methyl cellulose, enabling simultaneous quantification according to DP by HPLC/UV. Control of the HPLC-method was performed with a defined oligomer mixture obtained from beta-cyclodextrin. Results from LC-ESI-MS are discussed in comparison with those from syringe pump injection and compared to a calculated pattern for a random distribution. Programing of instrumental parameters optimized for each DP and avoidance of competition of successively eluting analytes in the electrospray process allowed extension of the established method for determination of the substitution pattern of cellulose derivatives along the polymer chain from DP5 to DP10 and thus a significant gain of information.
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| 46. |
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| 47. |
- Cumpstey, Ian
(författare)
-
Intramolecular aglycon delivery
- 2008
-
Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 343:10-11, s. 1553-1573
-
Forskningsöversikt (övrigt vetenskapligt/konstnärligt)
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| 48. |
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| 49. |
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| 50. |
- Dorst, Kevin, 1992-, et al.
(författare)
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NMR chemical shift prediction and structural elucidation of linker-containing oligo- and polysaccharides using the computer program CASPER
- 2023
-
Ingår i: Carbohydrate Research. - 0008-6215 .- 1873-426X. ; 533
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Tidskriftsartikel (refereegranskat)abstract
- Carbohydrate structures containing alkyl groups as aglycones are useful for investigating enzyme activity and glycan-protein interactions. Moreover, linker-containing oligosaccharides with a spacer group are commonly used to print glycan microarrays or to prepare protein-conjugates as vaccine candidates. The structural accuracy of these synthesized glycans are essential for interpretation of results from biological experiments in which the compounds have been used and NMR spectroscopy can unravel and confirm their structures. An approach for efficient 1H and 13C NMR chemical shift assignments employed a parallel NOAH-10 measurement followed by NMR spin-simulation to refine the 1H NMR chemical shifts, as exemplified for a disaccharide with an azidoethyl group as an aglycone, the NMR chemical shifts of which have been used to enhance the quality of CASPER (http://www.casper.organ.su.se/casper/). The CASPER program has been further developed to aid characterization of linker-containing oligo- and polysaccharides, either by chemical shift prediction for comparison to experimental NMR data or as structural investigation of synthesized glycans based on acquired unassigned NMR data. The ability of CASPER to elucidate structures of linker-containing oligosaccharides is demonstrated and comparisons to assigned or unassigned NMR data show the utility of CASPER in supporting a proposed oligosaccharide structure. Prediction of NMR chemical shifts of an oligosaccharide, corresponding to the repeating unit of an O-antigen polysaccharide, having a linker as an aglycone and a non-natural substituent derivative thereof are presented to exemplify the diversity of structures handled. Furthermore, NMR chemical shift predictions of synthesized polysaccharides, corresponding to bacterial polysaccharides, containing a linker are described showing that in addition to oligosaccharide structures also polysaccharide structures having an aglycone spacer group can be analyzed by CASPER.
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