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121.
Garcia SC Schott K Charão M Moro A Bulcão R Grotto D Valentini J Bohrer D Cardoso S Pomblum V 《Biomedical chromatography : BMC》2008,22(5):460-468
Reduced glutathione (GSH) is a well-known multifunctional antioxidant. Its depletion is linked to a number of pathologies, such as renal insufficiency. Feasible methodologies in clinical chemistry are vital. Therefore a methodology for GSH quantification was optimized and validated by HPLC-UV. Important aspects such as acid deproteinization and GSH stability were established. The erythrocytes were hemolyzed, deproteinized, derivatized with 5,5-dithio-bis (2-nitrobenzoic) acid and analyzed using HPLC, on an RP18 gradient elution, lambda=330 nm. The method was applied to hemodialysis patients (n=75) compared with healthy subjects (n=40). The assay was linear from 0.5 to 3.0 mm (r2>0.99). The intra- and inter-run reproducibilities were obtained with CV%<10%. The accuracy (bias %) ranged from 1.32 to -6.38%, and the recovery was >94%. The derivatized sample was stable for 60 days at -20 degrees C. The GSH levels in hemodialysis patients showed a significant increase compared with healthy subjects (p<0.05) and an inverse correlation with age (r=-0.286; p=0.013) was found. This method used UV detection, reduction of the phosphate concentration in the mobile phase and effective protein removal with trichloroacetic acid. The method proved to be reproducible, precise, accurate and stable. Thus, it can be suggested for routine laboratory tests for the verification of physiopathological conditions. 相似文献
122.
Proline chimeras are useful tools for medicinal chemistry and/or biological applications. The asymmetric synthesis of cis-3-substituted prolines can be easily achieved via amino-zinc-ene-enolate cyclization followed by transmetalation of the cyclic zinc intermediate for further functionalization. Syntheses of prolino-homotryptophane derivatives were achieved through Negishi cross-coupling of the zinc intermediate with indole rings. The use of Pd catalyst derived from Fu's [(t-Bu3)PH]-BF4 was required to avoid the undesired beta-hydride elimination. Optically pure and orthogonally protected compounds were obtained readily usable for peptide synthesis. 相似文献
123.
Flaviana T. Vieira Geraldo M. de Lima James L. Wardell Solange M.S.V. Wardell Klaus Krambrock Antnio F. de C. Alcntara 《Journal of organometallic chemistry》2008,693(11):1986-1990
The compound, [chloro{2(1H)-pyridinethione-S}{tris(pyridin-2-ylthiolato)methyl-C,N,N′,N″]}nickel(II)], [Ni(TPTM)(SPyH)Cl], was isolated from the reaction between NiCl2 · 6H2O and tris(pyridin-2-ylthiolato)methane in aqueous EtOH. X-ray crystallography at 120 K revealed an octahedral arrangement about Ni with a tetradentate tris(pyridin-2-ylthio)methyl-C,N,N,N ligand, a monodentate 2(1H)-pyridinethione-S ligand and a chloride. The 2(1H)-pyridinethione-S ligand was derived from tris(pyridin-2-ylthio)methane probably via an acid catalysed hydrolysis reaction. Intramolecular N–H–Cl and C–H–Cl interactions help to cement the molecular structure. Weak C–H–Cl and C–H–S hydrogen bonding interactions link molecules of [Ni(TPTM)(SPyH)Cl] into a 3D array. EPR and UV spectra, and Hartree–Fock theoretical calculations are reported. 相似文献
124.
Aussedat B Dupont E Sagan S Joliot A Lavielle S Chassaing G Burlina F 《Chemical communications (Cambridge, England)》2008,(12):1398-1400
Carriers with linear or dendrimeric structures displaying different functional groups were synthesized and their delivery properties were studied. 相似文献
125.
Wilton Pereira da Silva Cleide M. D. P. S. e Silva Vera Solange de O. Farias Diogo D. P. S. e Silva 《Heat and Mass Transfer》2010,46(3):371-380
A methodology for determination of the convective heat transfer coefficient, h
H, is proposed for fruits with spherical shape, using numerical simulation and experimental data of the temperature within
the fruit in the course of its cooling. In the proposed methodology, the position of the thermocouple inside the fruit is
assumed to be unknown, and can be obtained through several simulations, supposing different positions for this sensor. The
position of the thermocouple is then determined through analyses of the chi-squares of the simulations, which enabled to calculate
h
H. The proposed methodology was applied for an individual fig fruit, and the cooling kinetics was described in details. 相似文献
126.
Solange I. Mussatto George J. M. Rocha Inês C. Roberto 《Cellulose (London, England)》2008,15(4):641-649
Brewer’s spent grain (BSG) was evaluated for bleached pulp production. Two cellulose pulps with different chemical compositions
were produced by soda pulping: one from the original raw material and the other from material pretreated by dilute acid. Both
of them were bleached by a totally chlorine-free sequence performed in three stages, using 5% hydrogen peroxide in the two
initial, and a 0.25 N NaOH solution in the last one. Chemical composition, kappa number, viscosity, brightness and yield of
bleached and unbleached pulps were evaluated. The high hemicellulose (28.4% w/w) and extractives (5.8% w/w) contents in original
BSG affected the pulping and bleaching processes. However, soda pulping of acid pretreated BSG gave a cellulose-rich pulp
(90.4% w/w) with low hemicellulose and extractives contents (7.9% w/w and <3.4% w/w, respectively), which was easily bleached
achieving a kappa number of 11.21, viscosity of 3.12 cp, brightness of 71.3%, cellulose content of 95.7% w/w, and residual
lignin of 3.4% w/w. Alkaline and oxidative delignification of acid pretreated BSG was found as an attractive approach for
producing high-purity, chlorine-free cellulose pulp. 相似文献
127.
An imaging mass spectrometric method using laser ablation inductively coupled plasma spectrometry (LA-ICP-MS) was developed to determine Cu, Zn, Cd, Hg and Pb and metal distribution in longitudinal tissue sections of the marine snail Nassarius reticulatus (Gastropoda, Prosobranchia). Snails were sampled in northern Brittany (France) at three stations with different contamination levels.The quantification of metal distribution (imaging or mapping) in a thin slice of the snail tissue was carried out using different strategies: by one-point calibration and via matrix-matched laboratory standards using different biological materials (BCR 278, snail tissue, and rat brain). Together with the imaging of metals the distribution of two non-metals (carbon and sulfur) was analyzed. The imaging LA-ICP-MS analysis yielded an inhomogeneous distribution for all elements investigated. The detection limits for the distribution analysis of Cu, Zn, Cd, Hg and Pb measured by LA-ICP-MS were in the low μg g−1 range. 相似文献
128.
Francisco Antônio S. Cunha Rafael A. Sousa David P. Harding Solange Cadore Luciano F. Almeida Mário César U. Araújo 《Analytica chimica acta》2012
The principal thermodynamic advantages of using microemulsions over standard emulsions for flow metal analysis are the greatly increased analyte stability and emulsive homogeneity that improve both the ease of sample preparation, and the analytical result. In this study a piston propelled flow-batch analyzer (PFBA) for the determination of Cu, Cr and Pb in gasoline and naphtha by graphite furnace atomic absorption spectrometry (GF AAS) was explored. Investigative phase modeling for low dilution was conducted both for gasoline and naphtha microemulsions. Rheological considerations were also explored including a mathematical flow derivation to fine tune the system's operational parameters, and the GF AAS coupling. Both manual and automated procedures for microemulsion preparation were compared. The results of the paired t test at a 95% confidence level showed no significant differences between them. Further recovery test results confirmed a negligible matrix effect of the sample on the analyte absorption signals and an efficient stabilization of the samples (with metals) submitted to microemulsion treatment. The accuracy of the developed procedure was attested by good recovery percentages in the ranges of 100.0 ± 3.5% for Pb in the naphtha samples, and 100.2 ± 3.4% and 100.7 ± 4.6% for Cu and Cr, respectively in gasoline samples. 相似文献
129.
This paper is a study of the anisotropy induced in a silver chloride photographic emulsion by two successive beams of white light, linearly polarized at right angle. After the first exposure, the colloidal medium contains silver ellipsoids e generated by the photolysis of silver chloride and silver ellipsoids eb resulting of the partial destruction of some of the previous ones by long wavelengths. This medium is then illuminated by the second beam linearly polarized at right angle of the first beam. Short wavelengths induced silver ellipsoids e′ identical to the ellopsoids e but rotated through π/2 with respect to them. As in the first exposure, some of them are partly broken up and transformed into ellipsoids e′b identical to ellipsoids eb but the direction of their major axis. Moreover, the long wavelengths of second exposure transform some of the particles e and eb generated during the first exposure, into smaller ellipsoids eeb and ebb. Finally, the colloidal medium resulting of these two exposures, contains silver chloride and six sorts of silver particles. By calculating the indices of the medium, we show that the wavelengths characterizing the zero birefringence and zero dichroism of the emulsion are dependent on the energies recorded during each of the exposures. 相似文献
130.