Svein Halvor Knutsen - Academia.edu (original) (raw)
Papers by Svein Halvor Knutsen
Food Chemistry, Oct 1, 2021
While the harmonized INFOGEST model provides a physiologically relevant platform for simulated di... more While the harmonized INFOGEST model provides a physiologically relevant platform for simulated digestion, it needs to be combined with adequate analytical methods to enable quantification and comparison of protein digestibility in different food matrices. We have shown that size exclusion chromatography (SEC) can be used to estimate the proportion of small peptides potentially available for uptake. Combined with determination of total dissolved protein, the % of small peptides per total protein was calculated as a physiologically relevant estimate of protein digestibility (D SEC). Values for D SEC differed for casein (87.6%), chicken mince (72.6%), heated pea protein concentrate (67.8%), bread (63%), beef entrecote (57.7%) and pea protein concentrate (57.8%). In contrast to existing methods (TCA soluble protein, free NH 2-groups), the proposed SEC based method gives separate insight into the two fundamental processes during protein digestion (solubilization and breakdown), while maintaining the ability to rank digestibility of very different food proteins.
Additional file 3: Table S1. Determination of the 13C/1H correlation signals acquired in the 2D-N... more Additional file 3: Table S1. Determination of the 13C/1H correlation signals acquired in the 2D-NMR HSQC spectrum of MWL spruce. β-O-4 reflect the β-aryl ether as sketched in Additional file 1: Figure S1, G2, -5 and -6-reflects the aromatic signals and MeO reflects the methoxyl-group in the guaiacyl units sketched in Additional file 1: Figure S1. Table S2. Monosaccharide composition of carbohydrates in freeze dried aliquots of filtered, water soluble fractions. Table S3. Monosaccharide composition of dried residual biomass. Table S4. Acetate present in filtered slurry and released from solubilized carbohydrates in KOH treatment. Data from Fig. 2b, c and d.
PLOS ONE, 2019
Due to their antifungal activity, chitosan and its derivatives have potential to be used for trea... more Due to their antifungal activity, chitosan and its derivatives have potential to be used for treating yeast infections in humans. However, to be considered for use in human medicine, it is necessary to control and know the chemical composition of the compound, which is not always the case for polymeric chitosans. Here, we analyze the antifungal activity of a soluble and well-defined chito-oligosaccharide (CHOS) with an average polymerization degree (DP n) of 32 and fraction of acetylation (F A) of 0.15 (C32) on 52 medically relevant yeast strains. Minimal inhibitory concentrations (MIC) varied widely among yeast species, strains and isolates (from > 5000 to < 9.77 μg mL-1) and inhibition patterns showed a time-and dose-dependencies. The antifungal activity was predominantly fungicidal and was inversely proportional to the pH, being maximal at pH 4.5, the lowest tested pH. Furthermore, antifungal effects of CHOS fractions with varying average molecular weight indicated that those fractions with an intermediate degree of polymerization, i.e. DP 31 and 54, had the strongest inhibitory effects. Confocal imaging showed that C32 adsorbs to the cell surface, with subsequent cell disruption and accumulation of C32 in the cytoplasm. Thus, C32 has potential to be used as a therapy for fungal infections.
The main objective was to determine the influence of precursors regarding acrylamide formation in... more The main objective was to determine the influence of precursors regarding acrylamide formation in potato and cereals, and to develop methods for monitoring the bioavailability of this neurotoxin. T ...
Bioactive Carbohydrates and Dietary Fibre, 2016
The correct identification of immune-modulatory activity of polysaccharides is often hampered by ... more The correct identification of immune-modulatory activity of polysaccharides is often hampered by immune-stimulatory contaminants, with pyrogens such as lipopolysaccharide (LPS) as a very potent example. In order to avoid false positive immuno-stimulatory properties to be attributed to polysaccharides, accurate quantification and inactivation of LPS in test samples is crucial. To quantify LPS in polysaccharide preparations of different origin and structure we used two different limulus amoebocyte lysate test kits in two different laboratories. We observed larger variation in detection of LPS contamination between kits than between labs. LPS quantification proved unreliable for some polysaccharide preparations as spike controls resulted in spike recoveries outside the acceptable range. We designed a cellular in vitro assay as alternative method to detect the presence of functional LPS. This HEK-Blue hTLR4 cell culture provides a reliable assay, when combined with a cell viability test, for determining functional LPS in polysaccharide preparations. Finally, to inactivate LPS in polysaccharide preparations, we setup an alkaline-ethanol-based treatment. With this assay we observed that our treatment (5 h incubation in 0.1 M NaOH) at 56°C efficiently inactivated LPS in all polysaccharide preparations below immune-stimulatory levels. At this elevated temperature, however, we also observed minimal to severe degradation of polysaccharide preparations as determined with SEC-RI. Taken together, we describe methods and precautions to reliably detect and inactivate LPS in polysaccharide preparations to allow reliable in vitro investigations towards immune-modulatory potential of polysaccharide preparations.
Potato Research, 2016
In this study, the use of two modern portable blood glucose monitors (PBGMs) and a fruit juice-sp... more In this study, the use of two modern portable blood glucose monitors (PBGMs) and a fruit juice-specific system (RQFlex) from Merck was evaluated for determination of glucose concentrations in potato juice, as a representation of the whole potato. The two PBGMs (LifeScan OneTouch Ultra Easy and Bayer Contour) both provided squared correlation coefficients (R2, p < 0.001) of 0.92, when compared to reference analysis based on Anion Exchange Chromatography (HPAED-PAD).The LifeScan monitor gave an error estimation of 0.54 mg ml−1 but overestimated the glucose concentration by 20%. The Bayer monitor gave an error estimation of 1.12 mg ml−1 and underestimated the glucose concentration by 40%. The RQFlex system outperformed (R2 = 0.96, p < 0.001), error estimation of 0.24 mg mL−1) both the PBGMS, but this system is slightly more labour intensive to use than the PBGMs. A squared correlation coefficient of 0.91, p < 0.001, was found when comparing the glucose concentration in potato juice and content in lyophilized potato, indicating that sampling of potato juice may be introducing uncertainties to the measurements.
Carbohydrate Research, 1994
Carbohydrate Research, 2001
Oligosaccharides, enzymically produced from kappa-carrageenan, have been investigated by electros... more Oligosaccharides, enzymically produced from kappa-carrageenan, have been investigated by electrospray ionisation mass spectrometry (ESI-MS). The technique was used without prior derivatisation of the oligosaccharide originally obtained by size-exclusion chromatography (SEC). The structure of the oligosaccharides was mainly 4-sulphated neocarrabiose (A-G4S) with an increasing length ranging from di-to dodecasaccharides. However, in the larger oligosaccharides, structural motifs deviating from the perfect alternating A-G4S structure were detected, i.e. (A2S-G4S). Although resulting in reduced signal intensity, samples to which NaCl was added also gave rise to reliable mass spectra. Desulphation was induced at elevated cone voltages and in acidic or alkaline salt solutions.
Carbohydrate Research, 1992
The high-field 'H-NMR spectra of various carrageenan oligosaccharides at room temperature are giv... more The high-field 'H-NMR spectra of various carrageenan oligosaccharides at room temperature are given. The assignments were facilitated by the use of proton double-quantum coherence (DQCOSY) and 'H-13C chemical shift correlation 2D NMR spectroscopy, and by comparing high-field 'H-NMR spectra of various 4sulphated oligosaccharides of the neocarrabiose type. The effects of anomeric configuration on the 'H resonances on the same or neighbouring units are discussed. The '"C-NMR shift data are given for the tetrasaccharide of kappa-carrageenan.
Carbohydrate Polymers, 2012
The specific binding of the fluorescent dye calcofluor to cereal β-glucan results in increased fl... more The specific binding of the fluorescent dye calcofluor to cereal β-glucan results in increased fluorescence intensity of the formed complex and is in use for the quantification of β-glucan above a critical molecular weight (MW) by flow injection analysis. In this study, this method was applied in a fast and easy batch mode. In order to emphasize the spectral information of the emission spectra of the calcofluor/β-glucan complexes, derivative signals were calculated. A linear relationship was found between the amplitude of the second derivative signals and the β-glucan concentration between 0.1 and 0.4 μg/mL. The low detection limit of this new method (0.045 μg/mL) enabled its use to study the transport of cereal β-glucans over differentiated Caco-2 cell monolayers. Additionally, the method was applied to quantify β-glucan in arabinoxylan samples, which correlated well with data by an enzyme based method.
Carbohydrate Polymers, 1992
ABSTRACT Agar polymers were extracted with and without alkali pre-treatment from the red seaweed ... more ABSTRACT Agar polymers were extracted with and without alkali pre-treatment from the red seaweed Gracilaria dura, growing in the northern Adriatic Sea. Chemical analysis combined with 1H and 13C NMR spectroscopy showed that agar polysaccharides characterised by low methoxyl and fairly high pyruvate contents were obtained. Alkali pre-treatment markedly reduced the molecular weight and significantly increased the polydispersity of the extracted polymers. The native and alkali-treated agars exhibited comparable gelling and melting temperatures; however, the alkali-treated sample had higher gel strength than that of the native one. Chemical structure, molecular weight and rheological properties of the extracted galactans are discussed with regard to the algal source.
Carbohydrate Polymers, 1998
PMIa is a Type II arabinogalactan with anti-complementary activity isolated from the leaves of Pl... more PMIa is a Type II arabinogalactan with anti-complementary activity isolated from the leaves of Plantago major L. It has a molecular weight of 77 000-80000 Da and consists of arabinose (38%), galactose (49%), rhamnose (6%), galacturonic acid (7%) and 1.5% protein with hydroxyproline, alanine and serine as the main amino acids. Characterization of PMIa by methylation and GC-MS, methanolysis and GC, Smith degradation, weak acid hydrolysis, '3C-NMR, 'H-NMR, two-dimensional heteronuclear NMR and DEPT show that it consists of 1,3-linked galactan chains with 1,6-linked galactan side chains attached to position 6. The side chains are further branched in position 3 with 1,3-linked galactose residues which have 1,6-linked galactose attached to position 6; these 1,3-and 1,6-linked galactose chains altogether probably form a network. Terminal and 1,5-linked arabinose in furanose form are attached to the gala&an mainly through position 3 of the 1,6-linked galactose side chains.
Carbohydrate Polymers, 2008
... bedsores. The mechanism governing the wound healing property of plant material is not clear, ... more ... bedsores. The mechanism governing the wound healing property of plant material is not clear, but might be partly due to pectic substances triggering the immune system ([Hart et al., 1988] and [Samuelsen et al., 1995]). The ...
Carbohydrate Polymers, 1999
Polysaccharides were isolated from the seeds of Plantago major L. by water extraction and fractio... more Polysaccharides were isolated from the seeds of Plantago major L. by water extraction and fractionated by ion exchange and size exclusion chromatography. Methods such as methanolysis and GC, methylation analysis and GC-MS, weak acid hydrolysis, enzyme hydrolysis, 13 C, APT, 1 H and 2D heteronuclear (1 H± 13 C) chemical shift correlated NMR spectroscopy have revealed that the polysaccharides isolated are heteroxylans which consist of a 1,4-linked b-D-Xylp backbone with short side chains attached to position 2 in some 1,4-linked b-D-Xylp residues and to position 3 in other 1,4-linked b-D-Xylp residues. The side chains consist of b-D-Xylp, a-L-Araf, a-L-Araf 1 3 3 b-D-Xylp and aD -GlcpA1 3 3 a-L-Araf. 1,4-linked aD -GalpA residues were also detected in addition to small amounts of 1,2,4-linked Rhap and 1,3-, 1,6-and 1,3,6-linked Galp. The crude extract and some of the fractions obtained had potent anti-complementary activity.
Carbohydrate Polymers, 1992
ABSTRACT Carrageenans from Furcellaria lumbricalis and Eucheuma gelatinae were degraded by κ-carr... more ABSTRACT Carrageenans from Furcellaria lumbricalis and Eucheuma gelatinae were degraded by κ-carrageenase from Pseudomonas carrageenovora. Higher and lower molecular weight fractions were separated by ethanol precipitation and further fractionated by GPC on serially connected Sephacryl S-100 and S-200, and BioGel P4, respectively, and investigated by 500 MHz 1H NMR spectroscopy. Except for the lowest molecular weight oligosaccharide fractions from E. gelatinae, which contained di- and tetrasaccharides of κ-carrageenan, the lower molecular weight fractions of the carrageenans contained mixtures of neocarrabiose oligosaccharides with different content of d-galactose-4-sulphate. Both neocarrabiose and neocarrabiose-4-sulphate were detected on the non-reducing end. Varying with the source, the higher molecular weight fractions contained methyl, sulphate and other substitutions masking the general repeating backbone of neocarrabiose and neocarrabiose-4-sulphate.
Carbohydrate Polymers, 1994
ABSTRACT A low-sulfated carrageenan from Eucheuma gelatinae and a partially desulfated (by chemic... more ABSTRACT A low-sulfated carrageenan from Eucheuma gelatinae and a partially desulfated (by chemical means) furcellaran were studied by polarimetry and Cs-133 NMR. The polarimetric studies show that the cation specificity of the coil-helix transition remains a strong effect even for very low-sulfated carrageenans, whereas the sensitivity to inert salt is considerably weakened compared to unmodified furcellaran. Cs-133 NMR shifts and linewidths reveal a binding of Cs+ to the helical conformation, but not to the random coil. The cation specificity is well predicted by the theoretical model previously used for unmodified furcellaran and kappa-carrageenan, if it is assumed that the intrinsic binding constant and the density of binding sites are independent of the degree of sulfation of the carrageenan helix.
Food Chemistry, Oct 1, 2021
While the harmonized INFOGEST model provides a physiologically relevant platform for simulated di... more While the harmonized INFOGEST model provides a physiologically relevant platform for simulated digestion, it needs to be combined with adequate analytical methods to enable quantification and comparison of protein digestibility in different food matrices. We have shown that size exclusion chromatography (SEC) can be used to estimate the proportion of small peptides potentially available for uptake. Combined with determination of total dissolved protein, the % of small peptides per total protein was calculated as a physiologically relevant estimate of protein digestibility (D SEC). Values for D SEC differed for casein (87.6%), chicken mince (72.6%), heated pea protein concentrate (67.8%), bread (63%), beef entrecote (57.7%) and pea protein concentrate (57.8%). In contrast to existing methods (TCA soluble protein, free NH 2-groups), the proposed SEC based method gives separate insight into the two fundamental processes during protein digestion (solubilization and breakdown), while maintaining the ability to rank digestibility of very different food proteins.
Additional file 3: Table S1. Determination of the 13C/1H correlation signals acquired in the 2D-N... more Additional file 3: Table S1. Determination of the 13C/1H correlation signals acquired in the 2D-NMR HSQC spectrum of MWL spruce. β-O-4 reflect the β-aryl ether as sketched in Additional file 1: Figure S1, G2, -5 and -6-reflects the aromatic signals and MeO reflects the methoxyl-group in the guaiacyl units sketched in Additional file 1: Figure S1. Table S2. Monosaccharide composition of carbohydrates in freeze dried aliquots of filtered, water soluble fractions. Table S3. Monosaccharide composition of dried residual biomass. Table S4. Acetate present in filtered slurry and released from solubilized carbohydrates in KOH treatment. Data from Fig. 2b, c and d.
PLOS ONE, 2019
Due to their antifungal activity, chitosan and its derivatives have potential to be used for trea... more Due to their antifungal activity, chitosan and its derivatives have potential to be used for treating yeast infections in humans. However, to be considered for use in human medicine, it is necessary to control and know the chemical composition of the compound, which is not always the case for polymeric chitosans. Here, we analyze the antifungal activity of a soluble and well-defined chito-oligosaccharide (CHOS) with an average polymerization degree (DP n) of 32 and fraction of acetylation (F A) of 0.15 (C32) on 52 medically relevant yeast strains. Minimal inhibitory concentrations (MIC) varied widely among yeast species, strains and isolates (from > 5000 to < 9.77 μg mL-1) and inhibition patterns showed a time-and dose-dependencies. The antifungal activity was predominantly fungicidal and was inversely proportional to the pH, being maximal at pH 4.5, the lowest tested pH. Furthermore, antifungal effects of CHOS fractions with varying average molecular weight indicated that those fractions with an intermediate degree of polymerization, i.e. DP 31 and 54, had the strongest inhibitory effects. Confocal imaging showed that C32 adsorbs to the cell surface, with subsequent cell disruption and accumulation of C32 in the cytoplasm. Thus, C32 has potential to be used as a therapy for fungal infections.
The main objective was to determine the influence of precursors regarding acrylamide formation in... more The main objective was to determine the influence of precursors regarding acrylamide formation in potato and cereals, and to develop methods for monitoring the bioavailability of this neurotoxin. T ...
Bioactive Carbohydrates and Dietary Fibre, 2016
The correct identification of immune-modulatory activity of polysaccharides is often hampered by ... more The correct identification of immune-modulatory activity of polysaccharides is often hampered by immune-stimulatory contaminants, with pyrogens such as lipopolysaccharide (LPS) as a very potent example. In order to avoid false positive immuno-stimulatory properties to be attributed to polysaccharides, accurate quantification and inactivation of LPS in test samples is crucial. To quantify LPS in polysaccharide preparations of different origin and structure we used two different limulus amoebocyte lysate test kits in two different laboratories. We observed larger variation in detection of LPS contamination between kits than between labs. LPS quantification proved unreliable for some polysaccharide preparations as spike controls resulted in spike recoveries outside the acceptable range. We designed a cellular in vitro assay as alternative method to detect the presence of functional LPS. This HEK-Blue hTLR4 cell culture provides a reliable assay, when combined with a cell viability test, for determining functional LPS in polysaccharide preparations. Finally, to inactivate LPS in polysaccharide preparations, we setup an alkaline-ethanol-based treatment. With this assay we observed that our treatment (5 h incubation in 0.1 M NaOH) at 56°C efficiently inactivated LPS in all polysaccharide preparations below immune-stimulatory levels. At this elevated temperature, however, we also observed minimal to severe degradation of polysaccharide preparations as determined with SEC-RI. Taken together, we describe methods and precautions to reliably detect and inactivate LPS in polysaccharide preparations to allow reliable in vitro investigations towards immune-modulatory potential of polysaccharide preparations.
Potato Research, 2016
In this study, the use of two modern portable blood glucose monitors (PBGMs) and a fruit juice-sp... more In this study, the use of two modern portable blood glucose monitors (PBGMs) and a fruit juice-specific system (RQFlex) from Merck was evaluated for determination of glucose concentrations in potato juice, as a representation of the whole potato. The two PBGMs (LifeScan OneTouch Ultra Easy and Bayer Contour) both provided squared correlation coefficients (R2, p < 0.001) of 0.92, when compared to reference analysis based on Anion Exchange Chromatography (HPAED-PAD).The LifeScan monitor gave an error estimation of 0.54 mg ml−1 but overestimated the glucose concentration by 20%. The Bayer monitor gave an error estimation of 1.12 mg ml−1 and underestimated the glucose concentration by 40%. The RQFlex system outperformed (R2 = 0.96, p < 0.001), error estimation of 0.24 mg mL−1) both the PBGMS, but this system is slightly more labour intensive to use than the PBGMs. A squared correlation coefficient of 0.91, p < 0.001, was found when comparing the glucose concentration in potato juice and content in lyophilized potato, indicating that sampling of potato juice may be introducing uncertainties to the measurements.
Carbohydrate Research, 1994
Carbohydrate Research, 2001
Oligosaccharides, enzymically produced from kappa-carrageenan, have been investigated by electros... more Oligosaccharides, enzymically produced from kappa-carrageenan, have been investigated by electrospray ionisation mass spectrometry (ESI-MS). The technique was used without prior derivatisation of the oligosaccharide originally obtained by size-exclusion chromatography (SEC). The structure of the oligosaccharides was mainly 4-sulphated neocarrabiose (A-G4S) with an increasing length ranging from di-to dodecasaccharides. However, in the larger oligosaccharides, structural motifs deviating from the perfect alternating A-G4S structure were detected, i.e. (A2S-G4S). Although resulting in reduced signal intensity, samples to which NaCl was added also gave rise to reliable mass spectra. Desulphation was induced at elevated cone voltages and in acidic or alkaline salt solutions.
Carbohydrate Research, 1992
The high-field 'H-NMR spectra of various carrageenan oligosaccharides at room temperature are giv... more The high-field 'H-NMR spectra of various carrageenan oligosaccharides at room temperature are given. The assignments were facilitated by the use of proton double-quantum coherence (DQCOSY) and 'H-13C chemical shift correlation 2D NMR spectroscopy, and by comparing high-field 'H-NMR spectra of various 4sulphated oligosaccharides of the neocarrabiose type. The effects of anomeric configuration on the 'H resonances on the same or neighbouring units are discussed. The '"C-NMR shift data are given for the tetrasaccharide of kappa-carrageenan.
Carbohydrate Polymers, 2012
The specific binding of the fluorescent dye calcofluor to cereal β-glucan results in increased fl... more The specific binding of the fluorescent dye calcofluor to cereal β-glucan results in increased fluorescence intensity of the formed complex and is in use for the quantification of β-glucan above a critical molecular weight (MW) by flow injection analysis. In this study, this method was applied in a fast and easy batch mode. In order to emphasize the spectral information of the emission spectra of the calcofluor/β-glucan complexes, derivative signals were calculated. A linear relationship was found between the amplitude of the second derivative signals and the β-glucan concentration between 0.1 and 0.4 μg/mL. The low detection limit of this new method (0.045 μg/mL) enabled its use to study the transport of cereal β-glucans over differentiated Caco-2 cell monolayers. Additionally, the method was applied to quantify β-glucan in arabinoxylan samples, which correlated well with data by an enzyme based method.
Carbohydrate Polymers, 1992
ABSTRACT Agar polymers were extracted with and without alkali pre-treatment from the red seaweed ... more ABSTRACT Agar polymers were extracted with and without alkali pre-treatment from the red seaweed Gracilaria dura, growing in the northern Adriatic Sea. Chemical analysis combined with 1H and 13C NMR spectroscopy showed that agar polysaccharides characterised by low methoxyl and fairly high pyruvate contents were obtained. Alkali pre-treatment markedly reduced the molecular weight and significantly increased the polydispersity of the extracted polymers. The native and alkali-treated agars exhibited comparable gelling and melting temperatures; however, the alkali-treated sample had higher gel strength than that of the native one. Chemical structure, molecular weight and rheological properties of the extracted galactans are discussed with regard to the algal source.
Carbohydrate Polymers, 1998
PMIa is a Type II arabinogalactan with anti-complementary activity isolated from the leaves of Pl... more PMIa is a Type II arabinogalactan with anti-complementary activity isolated from the leaves of Plantago major L. It has a molecular weight of 77 000-80000 Da and consists of arabinose (38%), galactose (49%), rhamnose (6%), galacturonic acid (7%) and 1.5% protein with hydroxyproline, alanine and serine as the main amino acids. Characterization of PMIa by methylation and GC-MS, methanolysis and GC, Smith degradation, weak acid hydrolysis, '3C-NMR, 'H-NMR, two-dimensional heteronuclear NMR and DEPT show that it consists of 1,3-linked galactan chains with 1,6-linked galactan side chains attached to position 6. The side chains are further branched in position 3 with 1,3-linked galactose residues which have 1,6-linked galactose attached to position 6; these 1,3-and 1,6-linked galactose chains altogether probably form a network. Terminal and 1,5-linked arabinose in furanose form are attached to the gala&an mainly through position 3 of the 1,6-linked galactose side chains.
Carbohydrate Polymers, 2008
... bedsores. The mechanism governing the wound healing property of plant material is not clear, ... more ... bedsores. The mechanism governing the wound healing property of plant material is not clear, but might be partly due to pectic substances triggering the immune system ([Hart et al., 1988] and [Samuelsen et al., 1995]). The ...
Carbohydrate Polymers, 1999
Polysaccharides were isolated from the seeds of Plantago major L. by water extraction and fractio... more Polysaccharides were isolated from the seeds of Plantago major L. by water extraction and fractionated by ion exchange and size exclusion chromatography. Methods such as methanolysis and GC, methylation analysis and GC-MS, weak acid hydrolysis, enzyme hydrolysis, 13 C, APT, 1 H and 2D heteronuclear (1 H± 13 C) chemical shift correlated NMR spectroscopy have revealed that the polysaccharides isolated are heteroxylans which consist of a 1,4-linked b-D-Xylp backbone with short side chains attached to position 2 in some 1,4-linked b-D-Xylp residues and to position 3 in other 1,4-linked b-D-Xylp residues. The side chains consist of b-D-Xylp, a-L-Araf, a-L-Araf 1 3 3 b-D-Xylp and aD -GlcpA1 3 3 a-L-Araf. 1,4-linked aD -GalpA residues were also detected in addition to small amounts of 1,2,4-linked Rhap and 1,3-, 1,6-and 1,3,6-linked Galp. The crude extract and some of the fractions obtained had potent anti-complementary activity.
Carbohydrate Polymers, 1992
ABSTRACT Carrageenans from Furcellaria lumbricalis and Eucheuma gelatinae were degraded by κ-carr... more ABSTRACT Carrageenans from Furcellaria lumbricalis and Eucheuma gelatinae were degraded by κ-carrageenase from Pseudomonas carrageenovora. Higher and lower molecular weight fractions were separated by ethanol precipitation and further fractionated by GPC on serially connected Sephacryl S-100 and S-200, and BioGel P4, respectively, and investigated by 500 MHz 1H NMR spectroscopy. Except for the lowest molecular weight oligosaccharide fractions from E. gelatinae, which contained di- and tetrasaccharides of κ-carrageenan, the lower molecular weight fractions of the carrageenans contained mixtures of neocarrabiose oligosaccharides with different content of d-galactose-4-sulphate. Both neocarrabiose and neocarrabiose-4-sulphate were detected on the non-reducing end. Varying with the source, the higher molecular weight fractions contained methyl, sulphate and other substitutions masking the general repeating backbone of neocarrabiose and neocarrabiose-4-sulphate.
Carbohydrate Polymers, 1994
ABSTRACT A low-sulfated carrageenan from Eucheuma gelatinae and a partially desulfated (by chemic... more ABSTRACT A low-sulfated carrageenan from Eucheuma gelatinae and a partially desulfated (by chemical means) furcellaran were studied by polarimetry and Cs-133 NMR. The polarimetric studies show that the cation specificity of the coil-helix transition remains a strong effect even for very low-sulfated carrageenans, whereas the sensitivity to inert salt is considerably weakened compared to unmodified furcellaran. Cs-133 NMR shifts and linewidths reveal a binding of Cs+ to the helical conformation, but not to the random coil. The cation specificity is well predicted by the theoretical model previously used for unmodified furcellaran and kappa-carrageenan, if it is assumed that the intrinsic binding constant and the density of binding sites are independent of the degree of sulfation of the carrageenan helix.