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PubMed2004

Synergistic interactions between the genetically modified bacterial polysaccharide P2 and carob or konjac mannan.

Rheological studies have confirmed that the bacterial polysaccharide P2, a genetically modified variant of the Acetobacter xylinum polysaccharide acetan, undergoes synergistic gelation with either of the plant polysaccharides carob or konjac mannan. X-ray fibre diffraction data shows that P2 can form a 5-fold helical structure of pitch 4.7nm and an axial rise per disaccharide repeat of 0.92nm. Optical rotation data demonstrate that P2 undergoes a coil-helix transition in solution and that deacylation enhances the stability of the helical structure in solution. Studies made on mixtures prepared at different temperatures and ionic strengths suggest that denaturation of the P2 helix favours interaction and gelation. Deacetylation of P2 enhances gelation. X-ray diffraction data for oriented fibres prepared from deacetylated P2-konjac mannan mixed films reveal a 6-fold helical structure of pitch 5.54nm with an axial rise per disaccharide repeat also of 0.92nm. This mixed helix provides direct evidence for binding between the two polysaccharides. P2 contains two sites of acetylation: one on the backbone and one on the sidechain. The former site of acetylation inhibits helix formation for P2. It is suggested that this site of acetylation also inhibits formation of the mixed helix, explaining the enhanced gelation of mixtures on deacetylation.

Amorphophallus↗
PubMed2004

Structural analysis of arabinoxylans isolated from native and malted finger millet (Eleusine coracana, ragi).

Structural elucidation of purified arabinoxylans isolated from finger millet and its malt by methylation, GLC-MS, periodate oxidation, Smith degradation, NMR, IR, optical rotation, and oligosaccharide analysis indicated that the backbone was a 1,4-beta-D-xylan, with the majority of the residues substituted at C-3. The major oligosaccharide generated by endo xylanase treatment was homogeneous with a molecular weight of 1865 Da corresponding to 14 pentose residues as determined by MALDI-TOF-MS and gel filtration on Biogel P-2. The structural analysis of this oligosaccharide showed that it contained 8 xylose and 6 arabinose residues, substituted at C-3 (monosubstituted) and at both C-2 and C-3 (disubstituted).

Carbohydrate Sequence↗
PubMed2005

An alpha-glucan elicitor from the cell wall of a biocontrol binucleate Rhizoctonia isolate.

Binucleate Rhizoctonia (BNR) isolate (232-C6) is an effective biocontrol agent for protection of potato from Rhizoctonia canker, a disease caused by Rhizoctonia solani. Production of hydrolytic enzymes is one of the best known inducible defense responses following microbial infection. We isolated and characterized a cell wall alpha-glucan from BNR, which induces beta-1,3 glucanase activities in potato sprouts, the primary site of infection by R. solani. An autoclaving method, previously reported for isolation of oligosaccharide elicitors was used, and the glucan purified by chromatographic techniques. Maximal induction of beta-1,3 glucanase activity in potato sprouts was obtained with 250 microg of the alpha-glucan elicitor after 6 days from inoculation time. Both, BNR mycelium and the alpha-glucan produced a similar kinetic response of beta-1,3 glucanase. However, the alpha-glucan did not induce phytoalexin accumulation, previously correlated with the defense response. Uronic acids (approximately 10% with respect to total neutral sugars) were determined and identified as glucuronic acid by high-pH anion-exchange chromatography. Methylation analysis showed that the glucan consists of (1-->3) and (1-->4)-linked glucose units with preponderance of the first ones. Some of the (1-->4) linkages were branched at position 6. The glucan was partially degraded with amyloglucosidase. This, together with the NMR spectra data and the high optical rotation of the original (+195 degrees ) and degraded glucans (+175 degrees ) proved the alpha configuration. Further methylation of the amyloglucosidase degraded glucans indicated that they consist of (1-->3)-linked glucoses. The present study is the first report on the isolation and characterization of an alpha-glucan from Rhizoctonia, that may be important as a biocontrol factor.

Cell Wall↗
PubMed2005

Experimental approaches to hyaluronan structure.

A review of the literature describing experimental studies on hyaluronan (HA) is presented. Methods sensitive to the hydrodynamic properties of HA, analyzed in neutral aqueous solution containing NaCl at physiological concentration, can be shown to fit the expected behavior of a high molecular weight linear semi-flexible polymer. The significant nonideality of HA solutions can be predicted by a simple treatment for hydrodynamic interactions between polymer chains. Nuclear magnetic resonance and circular dichroism studies of HA are also in agreement with a model incorporating dynamically formed and broken hydrogen bonds, contributing to the semi-flexibility of the polymer chain, and segmental motions on the nanosecond time scale. HA shows the capability for self-association in the formation of a viscoelastic putty state at pH 2.5 in the presence of salt, and a gel state at pH 2.5 in mixed organic/aqueous solution containing salt. Ordered and associated structures have also been observed for HA on the surfaces, especially in the presence of surface-structured water. These phenomena can be understood in terms of counterion-mediated polyelectrolyte interactions. The possibility that hyaluronan exists in vivo in environments that induce ordered structures and assemblies is discussed.

Carbohydrate Conformation↗
PubMed2005

The structure of kappa/iota-hybrid carrageenans II. Coil-helix transition as a function of chain composition.

This paper describes the effect of the kappa/iota-ratio on the physical properties of kappa/iota-hybrid carrageenans (synonyms: kappa-2, kappa-2, weak kappa, weak gelling kappa). To this end, a series of kappa/iota-hybrid carrageenans ranging from almost homopolymeric kappa-carrageenan (98 mol-% kappa-units) to almost homopolymeric-carrageenan (99 mol-% iota-units) have been extracted from selected species of marine red algae (Rhodophyta). The kappa/iota-ratio of these kappa/iota-hybrids was determined by NMR spectroscopy. Their rheological properties were determined by small deformation oscillatory rheology. The gel strength (storage modulus, G') of the kappa/iota-hybrids decreases with decreasing kappa-content. On the other hand, the gelation temperature of the kappa-rich kappa/iota-hybrids is independent of their composition. This allows one to control the gel strength independent of the gelation or melting temperature. The conformational order-disorder transition of the kappa/iota-hybrids was studied using optical rotation and high-sensitivity differential scanning calorimetry. High-sensitivity DSC showed that the total transition enthalpy of the kappa/iota-hybrids goes through a minimum at 60 mol-% kappa-units, whereas for the mixture of kappa- and iota-carrageenan, the total transition enthalpy is a linear function of the composition. With respect to the ordering capability, the kappa/iota-hybrid carrageenans seem to behave as random block copolymers with length sequence distributions truncated from the side of the small lengths. Intrinsic thermodynamic properties (e.g., transition temperature and enthalpy) of kappa- and iota-sequences in these copolymers are close to those of their parent homopolymers. The critical sequence length for kappa-sequences is 2-fold of that for iota-sequences.

Carrageenan↗
PubMed2005

Separation of enantiomers of butorphanol and cycloamine by capillary zone electrophoresis.

Butorphanol tartrate is a synthetic opioid agonist-antagonist used as analgesic, possessing three chiral centres in the basic part of the molecule. Its chiral purity is routinely controlled only by optical rotation. A new capillary zone electrophoresis method, capable to separate the enantiomers of butorphanol and intermediate of its synthesis, cycloamine, was developed. Different electrolyte composition (type and concentration of carrier ion, pH, and organic solvent addition), and type and concentration of several chiral selectors (natural and modified cyclodextrins) were tested. Using the optimized conditions (acidic electrolyte with the addition of highly sulphated gamma-cyclodextrin) as low as 0.05% of undesirable enantiomers can be detected. Selected method characteristics, i.e., linearity (0-50 mg/l), precision (2.5% at 20 mg/l), and accuracy (101 +/- 2% at 20 mg/l) were evaluated. The optimized method was applied for the analysis of real batches of butorphanol and cycloamine. It was found that butorphanol tartrate manufactured by IVAX Pharmaceuticals contains less than 0.05% of undesirable enantiomer.

Butorphanol↗
PubMed2006

Chiral high-performance liquid chromatographic separation and circular dichroism spectra of the enantiomers of cytotoxic aristocularine alkaloids.

The HPLC enantiomeric separation of the racemic cularinoid alkaloids N-p-methoxy-1,alpha-dihydroaristoyagonine (1) and 4',5'-demethoxy-1,alpha-dihydroaristoyagonine (2) was accomplished using five chiral stationary phases (CSPs), some of them polysaccharide-derived ones. The molecular size and conjugative effect strongly affect the different enantioselectivity of the compounds 1 and 2 on the various CSPs investigated. Single enantiomers of 1 were isolated by repeated injections on an analytical HPLC column, and their circular dichroism spectra and optical rotations were measured. The cytotoxicity of the isolated enantiomers was measured on a human colon carcinoma cell line and compared with that of the racemic compound.

Alkaloids↗
PubMed2006

True and false reversal of the elution order of barbiturates on a bonded cellulose-based chiral stationary phase.

A set of racemic N-alkylated barbiturates were investigated for their direct enantioselective HPLC separation on a new chiral stationary phase (CSP) containing cellulose tris(3,5-dimethylphenylcarabamate) immobilized onto silica gel (Chiralpak IB) and its coated version (Chiralcel OD). They were online detected by UV and optical rotation detectors to trace the elution order of their enantiomers. Surprisingly, examples of false and true reversal of the elution order of enantiomers of barbiturates were observed and reported.

Barbiturates↗
PubMed2004

Thermoreversible gelation strongly coupled to coil-to-helix transition of polymers.

This paper theoretically studies thermoreversible gelation driven by aggregation of helices formed on the polymer chains. Two fundamentally different cases of (i) multiple association of single helices and (ii) association by multiple helices with multiplicity k (such as double helices (k=2), triple helices (k=3), etc.) are treated on the basis of different equations. The helix length distribution on a polymer chain (or assemble of chains for multiple helices) is derived as a function of polymer concentration and temperature. Theoretical calculation of the total helix content in the solution is compared with experimental data of optical rotation in iota-carrageenan solutions at different polymer concentrations. It is shown that at low temperature there is a sharp transition from network to bundle state (pair, triplet, etc.). To confirm such a network/pairing transition, we carried out Monte Carlo simulation of polymer solution in which hydrogen-bonded zipper-like cross-links are formed.

Gels↗
PubMed2004

The effect of the linear charge density of carrageenan on the ion binding investigated by differential scanning calorimetry, dc conductivity, and kHz dielectric relaxation.

The effect of the linear charge density of natural polyelectrolyte, carrageenan, on the ion binding to carrageenan molecules in relation to the gelation was investigated by using the dielectric relaxation spectroscopy, dc conductivity, optical rotation, and differential scanning calorimetry (DSC). Although carrageenan is an anionic polysaccharide, carrageenan molecules in the helix state at low temperatures can bind not only cation, such as potassium and cesium, but also anion, such as iodide. The dc conductivity steeply decreases just below the coil-helix transition temperature, which indicates the binding of ion to the carrageenan molecules in the helix state due to the increase of the linear charge density compared with that in the coil state. The addition of NaI promotes the helix formation, and prevents from aggregation of helices, which was suggested by the results of the dynamic shear modulus and the DSC, and resulted in an increase of the relaxation amplitude of the lowest frequency relaxation ( approximately kHz) attributed to the fluctuation of the tightly bound counter ions along the high charge density region (helix). It is concluded that binding of iodide induces (1) the increase in the amount of tightly bound counterions to carrageenan molecules and (2) the formation of non-aggregated helix.

Calorimetry, Differential Scanning↗
PubMed2004

Red blood cell aggregation during cardiopulmonary bypass: a pathogenic cofactor in endothelial cell activation?

OBJECTIVE: The bio-incompatibility of the cardiopulmonary bypass (CPB) circuit and the use of artificial colloids trigger massive defense reaction that involves endothelial cells and several blood cells: platelets, neutrophils, monocytes, red blood cells (RBC) and lymphocytes. Investigating the effects on RBC aggregation and endothelial cells activation, the present study addresses two different prime solutions commonly used in the clinical practice. METHODS: RBC aggregation was measured by means of Laser-assisted Optical Rotation Cell Analyzer, in an in vitro study designed to mimic the human blood-material interactions during extracorporeal circulation. A clinical study investigating endothelial activation was conducted in 20 patients undergoing elective coronary bypass surgery, randomly assigned for CPB using two different priming solutions: HAES-steril 6% (HES 200/0.5) and Voluven 6% (HES 130/0.4). RESULTS: Circulation trough a Chandler loop of HES-blood mixes altered significantly RBC aggregability. The use of HES 130/0.4 resulted in marked decrease in RBC aggregation (aggregation index (AI) before and after circulation was 23.5+/-3.8 and 18+/-2.9, respectively), no significant differences being found when compared with Ringer's lactate group. The use of HES 200/0.5 resulted in better maintained RBC aggregation (AI 39.7+/-5.9 and 29.7+/-4.7 before and after circulation, respectively). The AI measured for the whole blood (control) sample was 61.9+/-4.9 before circulation, and 58.1+/-4 after. Markers of endothelial activation (von Willebrand factor (vWF), thrombomodulin (TM), tissue plasminogen activator (tPA) and E-selectin) significantly increased during CPB. Differences between HES treatment groups were evident post-bypass. While the markers of endothelial activation returned to baseline in HES 200/0.5 group, HES 130/0.4 was associated on the first post-operative day with further increase of vWF and tPA. CONCLUSION: RBC aggregation significantly drooped as consequence of blood dilution and blood-material interaction. We reason that low RBC aggregation added to plasma viscosity reduction and non-physiologic flow conditions during extracorporeal circulation are important factors contributing to loss of shear stress at the venous endothelial wall. The loss of shear stress triggers complex signaling leading to endothelial activation. Additional fundamental research is needed in order to verify the hypothesis introduced by the present study. Characterizing the impact of rheologic parameters on endothelial function could prove to be valuable in patients undergoing CPB.

Adult↗
PubMed2004

Analytical and semipreparative resolution of enatiomers of albendazole sulfoxide by HPLC on amylose tris (3,5-dimethylphenylcarbamate) chiral stationary phases.

Broad spectrum anthelmintic agent-albendazole sulfoxide (ABZSO) have been separated and semiprepared on amylose tris (3,5-dimethylphenylcarbamate) chiral stationary phases by HPLC using mobile phases contained with n-hexane and different alcohols. For analytical separation the influence of the nature and content of alcoholic modifiers on separation were systemically studied. Then, the analytical methods were scaled up to semipreparative loading to obtain small quantities (about 1 g) of both ABZSO enantiomers. Especially, different loading amounts were investigated for their effect on various parameters of semipreparative HPLC. In addition, optical rotation and circular dichroism (CD) of both ABZSO enantiomers collected were determined and single enantiomers were found stable in configuration for 1 year.

Albendazole↗
PubMed2006

HPLC resolution of thioridazine enantiomers from pharmaceutical dosage form using cyclodextrin-based chiral stationary phase.

Resolution of racemic thioridazine obtained from Thioril tablets (Cipla Ltd., Goa, India) into its enantiomers has been achieved by HPLC using a beta-cyclodextrin (CD)-bonded stationary phase. Thioridazine was isolated from commercial formulations and was purified using preparative TLC. The purity was ascertained by RP-HPLC. For the resolution of rac-thioridazine using cyclodextrin based CSP and mobile phase of 0.05 M phosphate buffer (pH 6.5)-acetonitrile (50:50) was found to be successful. The optimum conditions of resolution were established by systematically studying the effect of organic modifier, concentration of buffer, pH and flow rate of mobile phase. The detection limit was found to be 10 microg (5 microg of each enantiomer). The enantiomeric purity of each of the resolved isomers was verified by optical rotation.

Buffers↗
PubMed2004

Two glucosylated abscisic acid derivates from avocado seeds (Persea americana Mill. Lauraceae cv. Hass).

Phytochemical investigation of avocado seed material (Persea americana Mill., Lauraceae) resulted in the isolation of two glucosylated abscisic acid derivates. One of these was not known as a natural product and can be regarded as a potential 'missing link' in abscisic acid metabolism in plants. After fractionation by high-speed countercurrent chromatography, and multiple steps of column chromatography, structures were elucidated by 1D-, 2D-NMR, electrospray-MS to be the novel beta-d-glucoside of (1'S,6'R)-8'-hydroxyabscisic acid, and (1'R,3'R,5'R,8'S)-epi-dihydrophaseic acid beta-d-glucoside. Absolute configuration was determined by circulardichroism, optical rotation, and by NOE experiments.

Abscisic Acid↗
PubMed2006

Diterpenes from the Far-eastern brown alga Dictyota dichotoma.

Two diterpenes, ent-erogorgiaene and (+)-1,5-cyclo-5,8,9,10-tetrahydroerogorgiaene, were isolated from the Russian Far-eastern population of the brown alga Dictyota dichotoma along with three previously known from this alga terpenoids. In addition, pentadecane was the first time isolated as natural product from this species. The structures of all compounds and their stereochemistry were determined using 1D and 2D NMR ((1)H-(1)H COSY, DEPT, HSQC, HMBC and NOESY), mass spectrometry, and optical rotation data.

Animals↗
PubMedDate not supplied

Solutions for organ perfusion and storage: haemorheologic aspects.

BACKGROUND: The hydroxyethyl starch (HES) contained in University of Wisconsin (UW) solution causes erythrocyte aggregation. The effect of UW on red blood cell (RBC) deformability is still unclear. HES-free preservation solutions, Celsior (CS) and Custodiol (CU) are available. In this study we evaluated whether they really showed a reduced aggregating and stiffening effect on RBCs when compared with UW. We was also evaluated the effect of these solutions on cellular membranes by measuring acetylcholinesterase (AChE), which is a marker of RBC membrane integrity. METHODS: The determination of RBC aggregation and deformability was performed by a laser-assisted optical rotation cell analyzer (LORCA). AChE measurement was performed with a spectrophotometric technique. RESULTS: The mean RBC aggregation index (AI) measured in pure blood control samples was 28.00 +/- 0.73%. The AI measured samples containing UW was 38.82 +/- 1.58%. In samples with CS, it was 13.307 +/- 0.64% and in samples with CU the mean AI was 12.47 +/- 0.42%. Also the RBC aggregating time was quicker in presence of UW compared with controls. AChE concentration in blood was 3.043 +/- 0.4 nmol. CS and UW did not produce any significant change; a significant reduction was found when CU was added to blood, namely 1.975 +/- 0.1 nmol (P < .05). The use of UW or CS or CU did not result in any significant change in RBC deformability. DISCUSSION: CS and CU solutions do not aggregate erythrocytes, whereas Wisconsin does massively. CU causes an alteration of RBC cellular membrane as demonstrated by depletion of AChE.

Acetylcholinesterase↗
PubMed2002

Stereoselective hydroxylation of 4-methyl-2-cyclohexenone in rats: its relevance to R-(+)-pulegone-mediated hepatotoxicity.

R-(+)-Pulegone, a monoterpene ketone, is a potent hepatotoxin. One of the major metabolites of pulegone has been shown to be p-cresol, a glutathione depletor and a known toxin. Allylic hydroxylation of 4-methyl-2-cyclohexenone results in the formation of p-cresol. The present study documents for the first time the involvement of cytochrome P-450 system and the stereochemical preference in this hydroxylation reaction. Incubation of PB-induced rat liver microsomes as well as reconstituted PB-induced cytochrome P-450 system with +/-4-methyl-2-cyclohexenone in the presence of NADPH and O(2) resulted in the formation of 4-hydroxy-4-methyl-2-cyclohexenone and p-cresol. From the assay mixture, the unreacted substrate, viz., 4-methyl-2-cyclohexenone was isolated and purified and its optical rotation was found to be 2.2 (in CHCl(3)). The observed enantiomeric excess in the recovered substrate was further confirmed by circular dichroism (CD) studies. The CD spectrum has a peak at 292nm and a trough at 270nm. The enantiomeric excess in the recovered substrate indicates that the hydroxylation at C-4 position is stereoselective. The significance of these results with respect to pulegone-mediated hepatotoxicity is discussed.

Animals↗