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931.
Pascal Gossart 《Analytica chimica acta》2003,477(2):201-209
The significance of evolving mixtures structural spectroscopic studies might appear limited when the experimental spectra do not present a sufficient quality for a precise interpretation. It is the case when the chemical behaviour of macromolecules is studied on the basis of infrared spectra. If the effective resolution is low, the spectral profiles appear similar despite the applied chemical conditions change. This makes impossible the interpretation of the raw spectra and mathematical treatments are required to separate the different contributions that overlap.To determine the behaviour of the reactive sites of humic acids in the binding with heavy metals, infrared spectra are recorded under various chemical conditions. The cation to be considered is Pb2+ and the two chemical variables to be studied are pH and initial lead concentration. Four series of FTIR spectra are recorded, but no visible difference can be directly assigned to the different chemical states of the macromolecules. Multivariate self-modelling curve resolution is thus proposed as a tool for resolving these complex and strong overlapping datasets. First, initial estimates are obtained from pure variable detection methods: it comes out that two spectra are enough to reconstruct the experimental matrices. In a further step, the application of the multivariate curve resolution-alternating least squares (MCR-ALS) algorithm with additional constraints on each individual dataset, as well as on column-wise augmented matrices, allows to optimise the profiles and spectra that appear to be highly characterising the acid and the salt form of the molecule. Moreover, the concentrations profiles associated to these two limit spectral forms allow interpreting the analytical measurements made during the reactions between humic acids and H+ or Pb2+. Consequently, depending on the initial state of the humic acid, two distinct reactional mechanisms are proposed. 相似文献
932.
Kumi Inoue Pascal Ferrante Yu Hirano Tomoyuki Yasukawa Hitoshi Shiku Tomokazu Matsue 《Talanta》2007,73(5):886-892
An immunochromatographic assay using nitrocellulose membrane was combined with electrochemical detection using an electrode chip in order to quantitatively detect testosterone as a model analyte. The electrode chip consisted of a gold working electrode, a counter electrode and a pseudo-reference electrode, all fabricated on the bottom of a 3.2 mm × 3.2 mm well. Competitive immunoreactions on the membrane were initiated by flowing a solution containing testosterone and horseradish peroxidase (HRP)-labeled testosterone (a competitor) over the membrane. Prepared membrane was placed in a solution containing ferrocenemethanol (FcOH) and H2O2 in the well of the electrode chip, and the enzyme reaction was detected by amperometry. Labeled HRP captured on the membrane catalyzed the oxidation of FcOH to the oxidized form FcOH+, which was reduced electrochemically by the electrode chip. The electrochemical response of the reduction current decreased with increasing concentration of testosterone over the range 1–625 ng/ml. 相似文献
933.
Guillaume Laconde Pascal Carato Jacques H. Poupaert Pascal Berthelot Patrick Depreux Jean-Pierre Hénichart 《Monatshefte für Chemie / Chemical Monthly》2003,134(7):1037-1043
Summary. This paper reports an one-pot method for the concomitant alkylation – oxidation (aromatization) of indolines, particularly
effective to get easy access to N-alkyl-6-nitroindoles, which are useful platforms in medicinal chemistry. N-alkyl-6-nitroindoles are obtained in good yield (64–91%) by reaction at room temperature in non-degassed DMF of 6-nitroindoline, an alkyl halide, and NaH as base. The presence of NaH appears to be essential for a high yield conversion.
Corresponding author. E-mail: pdepreux@phare.univ-lille2.fr
Received December 3, 2002; accepted December 9, 2002
Published online May 26, 2003 相似文献
934.
[structure: see text] We report the highly efficient preparation of well-defined tetravalent glycoconjugates as potential tools for cell targeting and cell-surface mimics. Our strategy is based on chemoselective assembly of aminooxy carbohydrates to a cyclic decapeptide template presenting aldehydes, namely, a "regioselectively addressable functionalized template" (RAFT). Preliminary recognition assays of tetramannosyl glycoconjugate (20) with specific lectin (Concanavalin A) using the fluorescence anisotropy method are also reported. 相似文献
935.
José-Henrique Pinto Donatien Pascal Kamden 《Applied biochemistry and biotechnology》1997,61(3):289-297
Five different chemical pretreatments, using dilute sulfuric acid, sodium hydroxide, hydrogen peroxide and sodium hydroxide,
peroxymonosulfate, and acetic acid, were applied to aspen thermomechanical fibers. The pretreated fibers were submitted to
enzymatic hydrolysis and the liberated glucose was monitored. High glucose concentrations were observed for the peroxymonosulfate
and the acetic acid pretreated samples. Glucose concentrations greater than 25 g/L were obtained in these cases. This corresponds
to conversions on the order of 90% of the pretreated substrate glucose content. 相似文献
936.
937.
Ben Sdira S Felix CP Giudicelli MB Seigle-Ferrand PF Perrin M Lamartine RJ 《The Journal of organic chemistry》2003,68(17):6632-6638
Chiral p-tert-butylcalix[4]arenes functionalized at the lower rim with amino acid residues have been prepared. The (1)H and (13)C NMR spectra indicate that the macrocycles preferably adopt a cone conformation. Calix[4]arenes bearing amino acid moieties were prepared as a class of receptors selective for anions that are bound through hydrogen bonding with the NH group. The association constants are dependent on the nature of the substituents at the lower rim. Derivative 9 shows the strongest complexation and the largest selectivity for N-tosyl-(L)-alaninate. Finally, a preliminary X-ray crystal study of the difunctionalized receptor 6f shows the "flattened cone" conformation in the solid state. 相似文献
938.
Nadjet Mezache Hocine Laouer Pascal Richomme Denis Séraphin Salah Akkal 《Natural product research》2019,33(15):2182-2191
Alkaloids and phenolic compounds are among the most biologically active natural products from the Jacobaea/Senecio genera (Asteraceae). To isolate original natural products directly from Jacobaea gigantea crude polar extracts, centrifugal partition chromatography (CPC) was used. Previously, we reported the phytochemical study of J. gigantea (syn. Senecio giganteus) n-butanol extract using various classical chromatographical techniques combined with CPC. Herein major constituents from the J. gigantea crude ethyl acetate extract and further compounds from the n-butanol extract were purified in only one step using this technique. A new pyrrolidine alkaloid, named senecipyrrolidine was isolated along with thirteen known compounds – chiro-inositol, three phenolic acids, six flavonoids, two quinones and emiline, another pyrrolidine alkaloid – from crude n-butanol or ethyl acetate extracts. Pyrrolidine alkaloids were isolated for the first time in the Jacobaea/Senecio genera and were probably biogenetically related to the two isolated quinones derivatives jacaranone and 3a-hydroxy-3,3a,7,7a-tetrahydrobenzofuran-2,6-dione, isolated in this species. 相似文献
939.
Blasius R Nierengarten H Luhmer M Constant JF Defrancq E Dumy P van Dorsselaer A Moucheron C Kirsch-Demesmaeker A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(5):1507-1517
[Ru(hat)2phen]2+ (HAT=1,4,5,8,9,12-hexaazatriphenylene, phen=1,10-phenanthroline) interacts with a good affinity with polynucleotides and DNA by intercalation, despite the presence of a second voluminous ancillary HAT ligand. It photoreacts with guanosine-5'-monophosphate (GMP). From HPLC, ESMS and NMR analyses, it can be concluded that this complex forms photoadducts with GMP. In contrast to the photoadducts isolated with Ru-TAP complexes (TAP=1,4,5,8-tetraazaphenanthrene), the photoadducts with [Ru(hat)2phen]2+ contain a covalent link between the oxygen atom of the guanine unit and a HAT ligand. Formation of oxidised photoadducts and compounds resulting from the addition of two GMP entities to the complex are also detected as side products. In the presence of oligo- and polynucleotides, [Ru(hat)2phen]2+ yields photoadducts when guanine bases are present. 相似文献
940.
Template assembled cyclopeptides as multimeric system for integrin targeting and endocytosis 总被引:6,自引:0,他引:6
Boturyn D Coll JL Garanger E Favrot MC Dumy P 《Journal of the American Chemical Society》2004,126(18):5730-5739
The alpha(V)beta(3) integrin receptor plays an important role in human metastasis and tumor-induced angiogenesis. c[-RGDfV-] peptide represents a selective alpha(V)beta(3) integrin ligand that has been extensively used for research, therapy, and diagnosis of neoangiogenesis. We report here the modular synthesis and biological characterization of template assembled cyclopeptides as a multimeric system for targeting and endocytosis of cells expressing alpha(V)beta(3) integrin. c[-RGDfK-] was cleanly assembled in a multivalent mode by chemoselective oxime bond formation to a cyclodecapeptides template labeled by different reporter groups. Binding propensity to the alpha(V)beta(3) receptor and the associated good uptake property displayed by the multivalent molecules demonstrated the interest in the RAFT molecule to design new multimeric system with hitherto unreported properties. These compounds offer an interesting perspective for the reevaluation of integrins as angiogenesis regulators (Hynes, R. O. Nature Med. 2003, 9, 918-921) as well as for the design of more sophisticated systems such as molecular conjugate vectors. 相似文献