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121.
Reducing end sugar residues in maltodextrins and arabinoxylans are determined as alditol acetates by gas-liquid chromatography following reduction, acid hydrolysis and acetylation of the samples. After this conversion to alditol acetates, the reducing end sugars are thus separated from their acetylated aldose counterparts. The method allows to identify individual reducing end sugars quantitatively and is a good alternative for colorimetric reducing sugar assays and 1H-NMR analysis. To demonstrate the advantages of the method, an application in a study of enzymic solubilisation and degradation of water unextractable arabinoxylan from a flour squeegee fraction is described. 相似文献
122.
The amidinoethylation of alcohols takes place by the addition of sodium alkoxides 2 (R1 = Me, Et) to the CC double bond of a variety of N,N'-substituted-propenamidines 1 (Method A). This illustrates the activation of the CC double bond by the conjugated amidine function and provides a new class of Michael acceptors for alcohols. However, this activation is poorer than with other nucleophiles or Michael acceptors. The amidinoethylation makes available 3-alkoxy-N,N'-substituted-amidines not easily accessible by other classical methods. However, it is demonstrated that the general N,N'-substituted-amidine synthesis via the nitrilium salts can also apply to nitrile compounds having an alkoxygroup present on the molecule (method B). Since the cyanoethylation of alcohols (4) is a very fast and facile reaction the method B is the preferred strategy for the synthesis of 3-alkoxy-N,N'-substituted-propanamidines 3. 相似文献
123.
The mass spectra of some N-methylpyridinium, quinolinium, isoquinolinium and phenanthridinium salts (R+X?) 1 The salt will be represented by R+X? or RX, R+ being the organic moiety, with its associated mass and X- the inorganic anion. are analyzed (X? = I? or ClO4?). For X? = I?, thermal decomposition gives rise mainly to the superimposed spectra of CH3I and the free base. Hence, iodide salts cannot be determined specifically by their mass spectra. When an α-methyl group is present, e.g. 2-methylpyridinium methiodide, elimination of HI becomes an important thermal process. For X? = ClO4?, the same pattern is observed, but in addition a generally important peak at [R + 15] is present. This peak is due to the oxidation, mainly α to the nitrogen of the organic moiety by the ClO4? ion, giving rise to the corresponding amide. In some cases, chlorination of the organic moiety has been observed as well as double oxidation. The thermal processes for the perchlorate salts are characteristic and are useful in the elucidation of the quaternary structure. 相似文献
124.
Both coiled open tubular reactors and packed-bed reactors can be used in flow analysis. Band broadening and pressure drop in these reactors are discussed. Theoretical analysis shows that packed-bed reactors are to be preferred. It is shown that for a given residence time and equal band-broadening values the pressure drop over a packed-bed reactor is lower than over a coiled open tubular reactor. Rules for optimal design are given for coiled tubular reactors and packed-bed reactors. The application of both reactors is shown for the spectrophotometric determination of phosphate with a vanadomolybdate reagent yielding a yellow colour. 相似文献
125.
Joris Van Loco Maureen Moerenhout Hedwig Beernaert 《Accreditation and quality assurance》2003,8(2):61-67
A GLP study can be performed at more than one site. This is called a multi-site study. Although, the study is performed at
different sites, it is still one study and must completely comply with the GLP principles. The fact that different activities
are conducted at different sites implies that the planning, the organization and the communication are crucial for the success
of the study. This means that all the staff involved should know their responsibilities and should have the knowledge and
skills to realize all the phases of the study according to the GLP principles. To achieve a well managed multi-site study,
several strategies for setting up such a study can be followed. This paper focuses on the responsibilities, communication,
and collaboration of the personnel, which are involved in a multi-site study. Several case studies are highlighted, and we
concluded that the basic communication triangle in a single-site GLP study between test facility management, study director,
and the quality assurance unit should be extended to the communication among test facility and test site management, study
director, principle investigator(s), and the quality assurance units at the test sites.
Introduction
Received: 14 August 2002 Accepted: 26 November 2002 相似文献
126.
A microwave-assisted click chemistry synthesis of 1,4-disubstituted 1,2,3-triazoles via a copper(I)-catalyzed three-component reaction 总被引:4,自引:0,他引:4
A microwave-assisted three-component reaction was used to prepare a series of 1,4-disubstituted-1,2,3-triazoles from corresponding alkyl halides, sodium azide, and alkynes. This procedure eliminates the need to handle organic azides, as they are generated in situ, making this already powerful click process even more user-friendly and safe. 相似文献
127.
13CT1 relaxation times for the different carbons of the sodium dodecyl sulphate chain in micellar systems have been measured, using Gd3+ as a paramagnetic relaxation reagent. The fluorescence decay of ω-(-naphthyl) dodecanoic acid, solubflized in the sodium dodecyl sulphate micelles was obtained in the presence of various amounts of counterion quencher Both series of experiments point to the occurrence of chain folding and to the fact that the terminal group can approach the Stern region of the micelle. 相似文献
128.
Mass spectrometric analysis of ceramide perturbations in brain and fibroblasts of mice and human patients with peroxisomal disorders 总被引:2,自引:0,他引:2
Pettus BJ Baes M Busman M Hannun YA Van Veldhoven PP 《Rapid communications in mass spectrometry : RCM》2004,18(14):1569-1574
In this study, the levels and composition of ceramides in brains of newborn mice lacking peroxisomes (Pex5-/-, Zellweger mice) were analyzed using normal-phase high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (HPLC/APCI-MS). Total ceramide compositions were found to be comparable to that of control animals. However, a minor ceramide species, containing hexacosanoic/hexacosenoic acid as the amide fatty acid, was 9-fold increased. Also, in the sphingomyelin-derived ceramides this species was elevated. Subsequent analysis of extracts from fibroblasts of Pex5-/- mice and mice with a defective peroxisomal beta-oxidation (lacking D-specific multifunctional protein 2 (MFP2)), revealed, again, a similar rise in this particular ceramide. Further, this ceramide was elevated in human X-ALD fibroblasts as well. Whether C26:1/0-ceramide is linked to some of the pathology seen in Zellweger syndrome remains to be investigated. However, an increase in this sphingolipid can be considered as a diagnostic criterion for diseases caused by defects in peroxisome biogenesis or peroxisomal beta-oxidation. 相似文献
129.
José M. Bartoloméa Jesús AlcázarJ.Ignacio Andrés Marcel De BruynJavier Fernández Encarna MatesanzKristof Van Emelen 《Tetrahedron letters》2003,44(47):8545-8548
The synthesis of a series of novel analogues of the 3-substituted-2,3-dihydro-1,4-dioxino[2,3-b]pyridine core, modified in the non-aromatic ring, is described. Due to the presence of a versatile hydroxymethyl group in their structure, these novel scaffolds are attractive intermediates for the preparation of potential new therapeutic agents. 相似文献
130.
Perfluoromethyl Element Ligands. XXIX. Preparation and Spectroscopic Investigation of M(CO)4L2 Complexes (M ? Cr, Mo, W; L ? Me2PSMe, Me2PSeMe, (CF3)2PSMe, (CF3)2PSMe) The complexes M(CO)4L2 (see Inhaltsübersicht) have been prepared by the reaction of tetracarbonyl norbornadiene metal compounds M(CO)4NBD with L at room temperature or 35°C, respectively. The cis-complexes formed in the first step undergo rearrangement to trans-isomers at higher temperatures. New compounds have been characterized by analytical and spectroscopic (IR, NMR, MS) methods. 相似文献