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51.
The lipase catalyzed resolution of trans-3,4-tetrahydrofuran and pyrrolidine bromohydrins by acylation or hydrolysis of their acylated derivatives has been studied. For both heterocycles, the best enantioselectivity was obtained using Candida antarctica lipase B as the catalyst in the hydrolytic processes. The enantiomerically pure bromohydrins are useful intermediates for the preparation of 3,4-fuctionalized cis-heterocycles. 相似文献
52.
53.
Rosa M. Claramunt Pilar Cornago M. Dolores Santa María Verónica Torres Elena Pinilla M. Rosario Torres 《Supramolecular chemistry》2013,25(4):349-356
The X-ray structure and the solid-state NMR measurements, mainly 15N CPMAS of the labelled compound, allow to determine the static and dynamic properties of 3(5)-ethyl-5(3)-phenyl-1H-pyrazole. The compound is a tetramer formed by three 5-ethyl-3-phenyl-1H-pyrazole and one 3-ethyl-5-phenyl-1H-pyrazole tautomers in dynamic equilibrium with the complementary situation. 相似文献
54.
Ioana Konz Beatriz Fernández M. Luisa Fernández Rosario Pereiro Héctor González Lydia Álvarez Miguel Coca-Prados Alfredo Sanz-Medel 《Analytical and bioanalytical chemistry》2013,405(10):3091-3096
Laser ablation coupled to inductively coupled plasma mass spectrometry has been developed for the elemental imaging of Mg, Fe and Cu distribution in histological tissue sections of fixed eyes, embedded in paraffin, from human donors (cadavers). This work presents the development of a novel internal standard correction methodology based on the deposition of a homogeneous thin gold film on the tissue surface and the use of the 197Au+ signal as internal standard. Sample preparation (tissue section thickness) and laser conditions were carefully optimized, and internal normalisation using 197Au+ was compared with 13C+ correction for imaging applications. 24Mg+, 56Fe+ and 63Cu+ distributions were investigated in histological sections of the anterior segment of the eye (including the iris, ciliary body, cornea and trabecular meshwork) and were shown to be heterogeneously distributed along those tissue structures. Reproducibility was assessed by imaging different human eye sections from the same donor and from ten different eyes from adult normal donors, which showed that similar spatial maps were obtained and therefore demonstrate the analytical potential of using 197Au+ as internal standard. The proposed analytical approach could offer a robust tool with great practical interest for clinical studies, e.g. to investigate trace element distribution of metals and their alterations in ocular diseases. Figure
Development of a new internal standard correction methodology for qualitative elemental imaging by LA-ICP-MS 相似文献
55.
Aline Bruna da Silva Juliano Marini Genaro Gelves Uttandaraman Sundararaj Rinaldo Gregório Jr. Rosario E.S. Bretas 《European Polymer Journal》2013
The objective of this work was to prepare novel conductive blends of poly(vinylidene fluoride) (PVDF) with polypyrrole (PPy) and to compare their performance with PVDF/multiwall carbon nanotube (MWCNT) composites and novel PVDF/PPy/MWCNT hybrid systems. All the compositions were prepared by melt mixing using a miniature mixer. The mixtures were characterized by Fourier transformed infrared (FTIR), wide angle X-ray diffraction (WAXD), thermogravimetric analyses (TGA), scanning and transmission electron microscopy (SEM and TEM, respectively) and volume electrical resistivity. For the binary PVDF/PPy and PVDF/MWCNT systems, percolation thresholds of 10 and 0.3 wt%, respectively, were found. In the hybrid systems, however, the percolation threshold for each filler was lower than in the binary systems, but the electrical conductivities were always much higher at all concentrations than the conductivities of the binary systems. Therefore, the addition of both fillers had a synergistic effect on the hybrid system conductivity, which was attributed to its morphology: the PPy increased the homogeneity of the MWCNT distribution and decreased the available free volume for the MWCNT; as a result the MWCNT rolled around the PPy particles bridging them through the PVDF matrix, increasing the quantum tunneling effect and thus, the electrical conductivity of the system. 相似文献
56.
Ptaquiloside, a potent carcinogen present in bracken fern, a plant consumed by farm animals, may be detected in traces by converting it into the bromopterosine. A simple synthesis of bromopterosine d2, to be used as standard in GC/MS or LC/MS analyses, is described. 相似文献
57.
M. Rosario De La Fuente Enrique Martín Miguel Ángel Pérez Jubindo Carmen Artal Blanca Ros José Luis Serrano 《Liquid crystals》2013,40(1):151-155
We present an achiral diacrylate that shows a phase transition from the synclinic smectic C phase (SmC) to the anticlinic smectic C (SmCalt). This last phase has been previously reported only for swallow-tailed or dimeric compounds. Our studies using differential scanning calorimetry, X-ray diffraction, polarizing optical microscopy and broad band dielectric spectroscopy suggest the existence of this mesophase in this bifunctional smectogen. 相似文献
58.
Vânia F. Pais Dr. Hamdy S. El‐Sheshtawy Prof. Dr. Rosario Fernández Prof. Dr. José M. Lassaletta Dr. Abel Ros Prof. Dr. Uwe Pischel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(21):6650-6661
A series of nine borylated arylisoquinolines has been prepared with systematic variation in their electronic properties and their photophysical properties were investigated. The color of their fluorescence can be finely tuned by changing the properties of the aryl moiety, which is involved in internal‐charge‐transfer processes. For example, methoxy‐substituted compound 5 showed an intense green emission, whereas dimethylamino‐substituted compound 6 showed an orange‐red emission. These new fluorophores were tested for their potential as molecular switches with external ionic stimuli, such as protons and fluoride ions. On the one hand, protonation of the isoquinoline moiety led to fluorescence enhancement for compounds that showed weak charge transfer and fluorescence quenching for compounds that showed strong charge transfer. On the other hand, the formation of ate complexes with fluoride led to strong fluorescence quenching in all of the investigated cases. 相似文献
59.
60.
Zamira Fetahaj Dr. Michel W. Jaworek Dr. Rosario Oliva Prof. Dr. Roland Winter 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(48):e202201658
The high colloidal stability of antibody (immunoglobulin) solutions is important for pharmaceutical applications. Inert cosolutes, excipients, are generally used in therapeutic protein formulations to minimize physical instabilities, such as liquid–liquid phase separation (LLPS), aggregation and precipitation, which are often encountered during manufacturing and storage. Despite their widespread use, a detailed understanding of how excipients modulate the specific protein-protein interactions responsible for these instabilities is still lacking. In this work, we demonstrate the high sensitivity to pressure of globulin condensates as a suitable means to suppress LLPS and subsequent aggregation of concentrated antibody solutions. The addition of excipients has only a minor effect. The high pressure sensitivity observed is due to the fact that these flexible Y-shaped molecules create a considerable amount of void volume in the condensed phase, leading to an overall decrease in the volume of the system upon dissociation of the droplet phase by pressure already at a few tens of to hundred bar. Moreover, we show that immunoglobulin molecules themselves are highly resistant to unfolding under pressure, and can even sustain pressures up to about 6 kbar without conformational changes. This implies that immunoglobulins are resistant to the pressure treatment of foods, such as milk, in high-pressure food-processing technologies, thereby preserving their immunological activity. 相似文献