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991.
In this work we report the purification of a crude acetin mixture into mono‐, di‐ and triacetin by countercurrent chromatography. The process was initially tested on a small, semi‐preparative scale (0.5 g) to determine its efficiency. The process was then scaled up to accommodate 2.5 g of crude reaction products containing a mixture of the acetins. The solvent system ethyl acetate/n‐butanol/water 1:0.2:1 was used in all separation procedures. Mono‐, di‐ and triacetins were separated similarly in the semi‐preparative and preparative runs. 相似文献
992.
José Valdilânio Virgulino Procópio Valmir Gomes de Souza Rodrigo Albuquerque da Costa Lidiane Pinto Correia Fábio Santos de Souza Rui Oliveira Macêdo 《Journal of Thermal Analysis and Calorimetry》2011,106(3):665-670
The simvastatin (SV) is nowadays produced semi-synthetically from lovastatin. It’s one of the statins most commonly used to
treat several forms of hypercholesterolemia. This study aimed to apply the thermal characterization of the SV raw material
using thermoanalytical techniques and its degradation products by Pyrolysis coupled to Gas chromatography/Mass spectrometry
(Pyr-GC/MS). It was studied three samples of SV (SVA, SVB, and SVC). The results showed thermal behavior differences of the
samples during the melting process transition and the activation energies (E
a) of the thermal decomposition, which were correlated to the thermal stability of them. The first decomposition step of Pyr-GC/MS
showed two new compounds of m/z 284 and 207, in proportions dependents according to the pyrolysis temperature. 相似文献
993.
Steroid and terpene chemistry still have a great impact on medicinal chemistry. Therefore, the development of new reactions or "greener" processes in this field is a contemporaneous issue. In this review, the use of bismuth(III) salts, as "ecofriendly" reagents/catalysts, on new chemical processes involving steroids and terpenes as substrates will be focused. Special attention will be given to some mechanistic considerations concerning selected reactions. 相似文献
994.
Neto LG Pinto Lda S Bastos RM Evaristo FF Vasconcelos MA Carneiro VA Arruda FV Porto AL Leal RB Júnior VA Cavada BS Teixeira EH 《Molecules (Basel, Switzerland)》2011,16(11):9298-9315
Lectins are a structurally heterogeneous group of highly specific carbohydrate-binding proteins. Due to their great biotechnological potential, lectins are widely used in biomedical research. The purpose of the present study was to evaluate the healing potential of the lectin of Bauhinia variegata (nBVL) and its recombinant isoform (rBVL-1). Following surgical creation of dorsal skin wounds, seven groups of mice were submitted to topical treatment for 12 days with lectin, D-galactose, BSA and saline. The animals were anesthetized and euthanized on POD 2, 7 and 12 in order to evaluate the healing potential of each treatment. The parameters considered included wound size, contraction rate, epithelialization rate and histopathological findings. Wound closure was fastest in animals treated with rBVL-1 (POD 7). nBVL was more effective than the controls. All skin layers were reconstructed and keratin deposition increased. Our findings indicate that the lectin of Bauhinia variegata possesses pro-healing properties and may be employed in the treatment of acute skin wounds. 相似文献
995.
Agna Hélia de Oliveira Elisana Afonso de Moura Márcia Ferraz Pinto José Valdilânio Virgulino Procópio Valmir Gomes de Souza Fábio Santos de Souza Rui Oliveira Macêdo 《Journal of Thermal Analysis and Calorimetry》2011,106(3):763-766
This work studied the thermal characterization of the pentoxifylline raw material through thermoanalytical techniques (TG,
DSC, DSC-photovisual) and analysis of degradation products by Pyr-GC/MS. The picture obtained with DSC-photovisual showed
the total vaporization of pentoxifylline at 230.0 °C. The TG dynamical curve presented only one step for the loss of mass
evidencing to be a kinetic process of zero order reaction. The pyrograms obtained for pentoxifylline sample in the solid state
and solution in the temperatures of 250.0, 300.0, and 400.0 °C, showed only one peak identifying the pentoxifylline. 相似文献
996.
Gates PJ Lopes NP Pinto E Colepicolo P Cardozo KH 《European journal of mass spectrometry (Chichester, England)》2011,17(5):481-484
This study reports the application of "double isolation" in sustained off-resonance irradiation collisionally-induced dissociation tandem mass spectrometry (SORI-CID-MS/MS) to remove radio- frequency (RF) fragment ions of very close mass isobaric ions (0.02 m/z apart). Analyses were performed with a fraction of a biological extract isolated from a macroalgae containing the mycosporine-like amino acid asterina-330. Direct isolation of the precursor ion by narrowing the isolation window proved ineffective as it impinged upon the required ion thus substantially reducing its intensity. By increasing the correlated sweep time, ejection efficiency of the isolation was improved, but caused the unwanted side-effect of RF fragmentation of labile ions. Finally, by skipping the ion activation step and performing a second isolation (in the MS(3) module) the RF fragments from the first isolation were removed leaving a very pure isolation of the required precursor ion and allowed a very clean CID fragmentation. We demonstrated that the m/z 272.1351 ion is derived from the loss of NH(3) from m/z 289.1620 isobaric impurity and is not related to asterina-330. This application represents a powerful tool to remove unwanted ions in the MS/MS spectrum that result from fragmentation of isobaric ions. 相似文献
997.
The phenazine monomers neutral red (NR) and methylene blue (MB) have been electropolymerised on different quartz crystal microbalance (QCM) substrates: MB at AuQCM and nanostructured ultrathin sputtered carbon AuQCM (AuQCM/C), and NR on AuQCM and on layer-by-layer films of hyaluronic acid with myoglobin deposited on AuQCM (AuQCM-{HA/Mb}(6)). The surface of the electrode substrates was characterised by atomic force microscopy (AFM), and the frequency changes during potential cycling electropolymerisation of the monomer were monitored by the QCM. The study investigates how the monomer chemical structure together with the electrode morphology and surface structure can influence the electropolymerisation process and the electrochemical properties of the phenazine-modified electrodes. Differences between MB and NR polymerisation, as well as between the different substrates were found. The electrochemical properties of the PNR-modified electrodes were analysed by cyclic voltammetry and electrochemical impedance spectroscopy and compared with the unmodified AuQCM. The results are valuable for future applications of modified AuQCM as substrates for electroactive polymer film deposition and applications in redox-mediated electrochemical sensors and biosensors. 相似文献
998.
Pinto RM Dias AA Costa ML Rodrigues P Barros MT Ogden JS Dyke JM 《The journal of physical chemistry. A》2011,115(30):8447-8457
Methyl 2-azidopropionate (N(3)CH(3)CHCOOCH(3), M2AP) has been synthesized and characterized by different spectroscopic methods, and the thermal decomposition of this molecule has been investigated by matrix isolation infrared (IR) spectroscopy and ultraviolet photoelectron spectroscopy (UVPES). Computational methods have been employed in the spectral simulation of both UVPES and matrix IR spectra and in the rationalization of the thermal decomposition results. M2AP presents a HOMO vertical ionization energy (VIE) of 9.60 ± 0.03 eV and contributions from all four lowest-energy conformations of this molecule are detected in the gas phase. Its thermal decomposition starts at ca. 400 °C and is complete at ca. 650 °C, yielding N(2), CO, CO(2), CH(3)CN, and CH(3)OH as the final decomposition products. Methyl formate (MF) and CH(4) are also found during the pyrolysis process. Analysis of the potential energy surface of the decomposition of M2AP indicates that M2AP decomposes preferentially into the corresponding imine (M2IP), through a 1,2-H shift synchronous with the N(2) elimination (Type 1 mechanism), requiring an activation energy of 160.8 kJ/mol. The imine further decomposes via two competitive routes: one accounting for CO, CH(3)OH, and CH(3)CN (ΔE(G3) = 260.2 kJ/mol) and another leading to CO(2), CH(4), and CH(3)CN (ΔE(G3) = 268.6 kJ/mol). A heterocyclic intermediate (Type 2 mechanism)-4-Me-5-oxazolidone-can also be formed from M2AP via H transfer from the remote O-CH(3) group, together with the N(2) elimination (ΔE(G3) = 260.2 kJ/mol). Finally, a third pathway which accounts for the formation of MF through an M2AP isomer is envisioned. 相似文献
999.
Nogueira Kde O Araújo VA Rodrigues Sartori SS Neves CA 《Micron (Oxford, England : 1993)》2011,42(5):377-380
Hemidactylus mabouia is an Africa oviparous lizard that is now distributed on other continents and has been introduced to Brazil. In the majority of reptiles, the females have the ability to store spermatozoa in specialized regions of the genital tract. Considering that in H. mabouia the storage of spermatozoa is restricted to the region of the uterine tube, in this study we utilized optical and transmission electron microscopy to investigate the processes related to the large number of spermatozoa in the vagina. Although it was possible to visualize spermatozoa in the vagina, an ultrastructural analysis of the region revealed that significant phagocytosis occurs, which is mediated by the epithelial cells. Such a process indicates that the anterior portion of the vagina is related to the elimination of supernumerary or deficient spermatozoa and not storage. 相似文献
1000.
Luís P. Martins Álvaro J. Almeida Nuno A. Silva Paulo S. André Armando N. Pinto 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2014,68(8):1-5
The solution to Bell theorem for N-qubits was widely studied in [M. ?ukowski, ?. Brukner, Phys. Rev. Lett. 88, 210401 (2002)]. Here we present a different way to obtain the solution of that theorem for the dichotomic experiment. In order to obtain a solution for the Werner-Wolf-?ukowski-Brukner WW?B inequality a new correlation function is proposed. This new correlation function expresses directly the constraints imposed by local theories. We use the general Greenberger-Horne-Zeilinger (GHZ) state, whereof, as it is well known, emerges a family of entangled states that do not violate the WW?B inequality [M. ?ukowski, ?. Brukner, W. Laskowski, M. Wie?niak, Phys. Rev. Lett. 88, 210402 (2002)], i.e. it can be described by a local realistic theory, to illustrate our results. 相似文献