RÉSUMÉ
Polypropyleneimines (PPIs) functionalized by glycerol-based entities are prepared and characterized by diffusion-ordered spectroscopy NMR. Showing low cytotoxicity against MRC5 fibroblasts, their encapsulation capacities of gadolinium complexes was evaluated. T(1) measurements were performed to determine the relaxivity of the encapsulated gadopentetate dimeglumine (GdBOPTA) in dendrimers of fourth and fifth generation (GD-PPI-4 and GD-PPI-5). Comparison of the GdBOPTA relaxivity and the relaxivity of GdBOPTA-loaded dendrimers showed a slight increase of the gadolinium chelate relaxivity.
Sujet(s)
Produits de contraste/composition chimique , Dendrimères/composition chimique , Acide gadopentétique/composition chimique , Polypropylènes/composition chimique , Lignée cellulaire , Produits de contraste/pharmacologie , Dendrimères/pharmacologie , Évaluation préclinique de médicament , Fibroblastes/cytologie , Fibroblastes/métabolisme , Acide gadopentétique/pharmacologie , Humains , Polypropylènes/pharmacologieRÉSUMÉ
The complete assignment of the (1)H and (13)C sugar resonances in mono-3,6-anhydro-heptakis(2,3-O-methyl)-hexakis(6-O-methyl)-ß-cyclodextrin, an asymmetrically functionalized ß-cyclodextrin, was carried out by means of 2D NMR experiments. The TOCSY and the homonuclear multiple relay COSY spectra provided most of the (1)H assignments. The multiplicity edited HSQC and a set of F(1) selective HSQC-TOCSY and multiple relay HSQC-COSY spectra gave access to most of the (13)C chemical shifts. The latter were fully and accurately determined by means of a pair of complementary, highly folded HSQC-TOCSY spectra. The TOCSY-ROESY and ROESY-TOCSY spectra yielded the sequential assignment of the sugar units. A high resolution F(1) selective F(1) decoupled version of the TOCSY-ROESY experiment was recorded.
RÉSUMÉ
Chitinases and thaumatin-like proteins are important grape proteins as they have a great influence on wine quality. The quantification of these proteins in grape juices and wines, along with their purification, is therefore crucial to study their intrinsic characteristics and the exact role they play in wines. The main isoforms of these two proteins from Chardonnay grape juice were thus purified by liquid chromatography. Two fast protein liquid chromatography (FLPC) steps allowed the fractionation and purification of the juice proteins, using cation exchange and hydrophobic interaction media. A further high-performance liquid chromatography (HPLC) step was used to achieve higher purity levels. Fraction assessment was achieved by mass spectrometry. Fraction purity was determined by HPLC to detect the presence of protein contaminants, and by nuclear magnetic resonance (NMR) spectroscopy to detect the presence of organic contaminants. Once pure fractions of lyophilized chitinase and thaumatin-like protein were obtained, ultra-HPLC (UHPLC) and enzyme-linked immunosorbent assay (ELISA) calibration curves were constructed. The quantification of these proteins in different grape juice and wine samples was thus achieved for the first time with both techniques through comparison with the purified protein calibration curve. UHPLC and ELISA showed very consistent results (less than 16% deviation for both proteins) and either could be considered to provide an accurate and reliable quantification of proteins in the oenology field.
Sujet(s)
Boissons/analyse , Chitinase/isolement et purification , Protéines végétales/isolement et purification , Vitis/composition chimique , Vin/analyse , Chromatographie en phase liquide à haute performance , Test ELISA , Résonance magnétique nucléaire biomoléculaireRÉSUMÉ
Spin system selective 1D (1)H, 2D DQF-COSY and 2D HSQC NMR spectra were recorded in order to fully assign the (1)H and (13)C 1D NMR spectra of an asymmetrical beta-cyclodextrin derivative. Instead of individually accessing the seven sugar anomeric protons by means of long multiplet selective pulses, only short region selective pulses were used. The simultaneously selected anomeric protons were differentiated by allowing their magnetization to evolve under the sole effect of the chemical shift interaction. In each experiment, the seven recorded spectra were linear combinations of the seven desired ones. The combination coefficients were measured and used to obtain almost perfectly separated sugar unit sub-spectra. This multiplexed acquisition scheme resulted in a time gain factor of about 2.
Sujet(s)
Spectroscopie par résonance magnétique/méthodes , Glucides/composition chimique , Protons , Cyclodextrines bêta/composition chimiqueRÉSUMÉ
This work deals with the synthesis of two mixed binary chiral selectors prepared by grafting (L)- or (D)-valine tert-butylamide on permethylated cyclodextrin macrocycle. The enantioselective properties of the new chiral selectors diluted in OV11 polysiloxane (35% phenyl- and 65% methylsiloxane) were investigated by means of injections of 117 racemic mixtures. The mixed chiral selectors with (L)-valine and, to a lesser extent with (D)-valine, were found to have an improved enantioselectivity toward amino acid derivatives by comparison to permethylated cyclodextrin. The enantioseparation capability of these new chiral selectors has proven to be slightly less efficient than Chirasil-L-Val (Alltech) for amino acid derivatives, but it has been extended to include terpenes, lactones, esters, aliphatic compounds and aryl alcohols.
Sujet(s)
Valine/composition chimique , Cyclodextrines bêta/composition chimique , Chromatographie en phase gazeuse/instrumentation , Chromatographie en phase gazeuse/méthodes , Stéréoisomérie , Valine/analogues et dérivés , Valine/synthèse chimique , Cyclodextrines bêta/synthèse chimiqueRÉSUMÉ
Oleanolic acid, scoparone, scopoletin and a novel iridoid derivative, angelone, were isolated from Tachiadenus longiflorus (Gentianaceae). The structure of angelone was determined from NMR data, given as input to the Logic for Structure Determination Programme, and was finally confirmed by comparison of experimental 13C-NMR chemical shifts with those obtained by quantum mechanical calculations.
Sujet(s)
Gentianaceae/composition chimique , Iridoïdes/composition chimique , Pyrones/composition chimique , Logiciel , Structure moléculaire , Écorce/composition chimique , Tiges de plante/composition chimiqueRÉSUMÉ
Centrifugal partition chromatography in the ion-exchange displacement mode allowed a preparative and efficient fractionation of low-molecular-mass heparins from enoxaparin sodium. Amberlite LA2--a lipophilic liquid secondary amine--was chosen as a weak anion exchanger. The biphasic system methyl isobutyl ketone-water was selected. Protonated LA2 (10%, v/v) was added to the organic stationary phase. Hydroxide (Na+, OH-) was chosen as a displacer in the aqueous mobile phase. The observed pH and concentration profiles are typical of displacement chromatography, as supported by numerical simulation. The Dubois test for the analysis of sugar content and an analysis of sulfur content (and consequently sulfatation rate) were carried out to monitor the effectiveness of the procedure. Moreover, the fractions were analyzed by high-performance size-exclusion chromatography and the 1H NMR spectra confirmed the fractionation of the sample of enoxaparin sodium.
Sujet(s)
Chromatographie d'échange d'ions/méthodes , Héparine bas poids moléculaire/isolement et purification , Chromatographie sur gel/méthodes , Chromatographie en phase liquide à haute performance/méthodes , Concentration en ions d'hydrogène , Spectroscopie par résonance magnétique , Masse moléculaireRÉSUMÉ
To investigate the functions of debranching enzymes in starch biosynthesis, we have partially purified and characterized these activities from wild type and mutant sta7 Chlamydomonas reinhardtii. Mutants of the STA7 locus substitute synthesis of insoluble granular starch by that of small amounts of glycogen-like material. The mutants were previously shown to lack an 88 kDa debranching enzyme. Two distinct debranching activities were detected in wild-type strains. The 88 kDa debranching enzyme subunit missing in glycogen-producing mutants (CIS1) is shown to be part of a multimeric enzyme complex. A monomeric 95 kDa debranching enzyme (CLD1) cleaved alpha-1,6 linkages separated by as few as three glucose residues while the multimeric complex was unable to do so. Both enzymes were able to debranch amylopectin while the alpha-1,6 linkages of glycogen were completely debranched by the multimeric complex only. Therefore CLD1 and the multimeric debranching enzyme display respectively the limit-dextrinase (pullulanase) and isoamylase-type specificities. Various mutations in the STA7 locus caused the loss of both CIS1 and of the multimeric isoamylase complex. In contrast to rice and maize mutants that accumulate phytoglycogen owing to mutation of an isoamylase-type DBE, isoamylase depletion in Chlamydomonas did not result in any qualitative or quantitative difference in pullulanase activity.
RÉSUMÉ
The hexane extract of the bark of Entandrophragma delevoyi has yielded a novel tetranortriterpenoid, delevoyin C. This compound contains a cyclobutanyl ring incorporating C-19 and a cycloheptanyl ring C including C-30. Gedunin and 11beta-Acetoxygedunin were isolated from the hexane extract of the wood.
Sujet(s)
Arbres/composition chimique , Triterpènes/isolement et purification , Hexanes , Spectroscopie par résonance magnétique , Extraits de plantes/composition chimique , Triterpènes/composition chimiqueRÉSUMÉ
The stem bark of Astrotrichilia voamatata (Meliaceae) has yielded the novel limonoids voamatins C and D. These compounds represent a new type of pentanortriterpenoid and are unique in containing a ring A cyclic ether.
Sujet(s)
Arbres/composition chimique , Triterpènes/composition chimique , Spectroscopie par résonance magnétique , Triterpènes/isolement et purificationRÉSUMÉ
Hydrolysis of wheat bran and wheat straw by a 20.7 kDa thermostable endoxylanase released 35 and 18% of the cell-wall xylan content, respectively. Separation of the cinnamoyl-oligosaccharides (accounting for 6%) from the bulk of total oligosaccharides was achieved by specific anion-exchange chromatography. The cinnamoyl-oligosaccharides were further purified by preparative paper chromatography (PPC) and their molecular weight was determined by MALDI-TOF mass spectrometry. The partially purified hydrolysis end-products contained from 4 to 16 and from 4 to 12 pentose residues for wheat bran and straw, respectively, and only one cinnamic acid per molecule. The primary structure of the new feruloyl arabinoxylopentasaccharide from wheat bran hydrolysis, which has been determined using 2D NMR spectroscopy, is O-beta-D-xylopyranosyl-(1-->4)-O-[5-O- (feruloyl)-alpha-L-arabinofuranosyl-(1-->3)]-O-beta-D-xylopyranosy l-(1-->4) -O-beta-D-xylopyranosyl-(1-->4)-D-xylopyranose.
Sujet(s)
Cinnamates/synthèse chimique , Oligosaccharides/synthèse chimique , Triticum/composition chimique , Xylosidases/composition chimique , Séquence glucidique , Chromatographie d'échange d'ions , Endo-1,4-beta xylanases , Hydrolyse , Données de séquences moléculaires , Structure moléculaireRÉSUMÉ
Centrifugal partition chromatography (CPC) in the pH-zone refining mode allowed a preparative and efficient isolation of vindoline, vindolinine, catharanthine and vincaleukoblastine from a crude mixture of Catharanthus roseus alkaloids. The separation protocol was tested with a synthetic mixture of vindoline, catharanthine and vincaleukoblastine. The fraction content was analyzed and the results compared with theoretical chromatograms obtained by numerical simulation. The increase in injected sample mass results in an improvement of the purity of the isolated compounds. This observation, confirmed by theory, is of prime importance for the development of preparative pH-zone refining CPC as a preparative separation method.
Sujet(s)
Chromatographie/méthodes , Indoles/isolement et purification , Alcaloïdes de Vinca/isolement et purification , Concentration en ions d'hydrogèneRÉSUMÉ
Variants of the HSQC and HMBC experiments are described. They allow the restriction of the heteronuclear chemical shift domain without causing spectral folding. Selectivity is introduced in the HSQC experiment by means of excitation sculpting. The selective element of the pulse sequence is a double pulsed field gradient spin echo. It may be used either split by the t(1) evolution period, or not. The selectivity profile depends on the scheme used as well as on the number of protons attached to the heteronucleus. The selective HMBC experiment requires only a single echo sequence as no strict control of the signal phase is required. A complex glycoconjugate is used as a test compound for the new pulse sequences.
Sujet(s)
Spectroscopie par résonance magnétique/méthodesRÉSUMÉ
The concept of blind source separation is described and examples of its use in 1D and 2D NMR spectroscopy are presented. The goal of this data processing method is to extract the spectra of components molecules when only mixtures are available. Copyright 1998 Academic Press.
RÉSUMÉ
1H NMR spectroscopy assignments have been obtained for starch acetates using COSY and HOHAHA experiments by comparison with the spectra of amylose triacetate and of peracetylated malto-oligosaccharides (maltotriose, maltotetraose, maltoheptaose). These assignments are valuable for the location and evaluation of the substitution pattern in modified starches. The bulk of the 1H NMR spectra of highly acetylated starch strongly resembles the spectrum of amylose triacetate in which all protons are identified and display distinct chemical shifts. The resolving power of the HOHAHA experiment allowed the distinction of minor spin systems. Beside these strong signals pertaining to an average 2.3.6-tri-O-acetyl-alpha-(1-->4) linked D-glucopyranose unit in an infinite chain, the combination of COSY and HOHAHA experiments allowed the identification of these systems to the terminal, n-1, n-2, and to partially acetylated glucopyranosyl units. As an example, two different preparations of starch acetates with degrees of substitution 2.74 and 2.63 were examined. In one case, NMR demonstrates that the defects of acetylation are random on the polymeric chain (with corresponding signals for unacylated secondary hydroxyl positions at delta 3.61 and 3.40) while in another case, these signals are not detectable, probably due to the presence of clusters of non-acetylated residue forming solid-like zones.
Sujet(s)
Glucose/composition chimique , Spectroscopie par résonance magnétique/méthodes , Amidon/analogues et dérivés , Acétylation , Séquence glucidique , Données de séquences moléculaires , Oligosaccharides/composition chimique , Protons , Amidon/composition chimiqueRÉSUMÉ
Eleven known indole alkaloids: vallesine, aspidospermine, 11-methoxydichotine, apparicine, tubotaïwine, vincadifformine, condylocarpine, (-)-rhazinilam, aspidospermatine, haplocidine, and 18-oxohaplocidine, have been isolated from leaves and stems of Vallesia glabra (Cav.) Link. (Apocynaceae) from Bolivia. Analysis of 2 D NMR spectra complete previous 1H and 13C data for vallesine, aspidospermine, and 11-methoxydichotine.