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131.
132.
Luca Guideri Rossella Noschese Fabio Ponticelli 《Journal of heterocyclic chemistry》2012,49(2):297-302
1‐benzyl‐5‐(ethoxycarbonyl)‐2,3,4,5‐tetrahydropyridinium bromide undergoes ring contraction with a series of nucleophiles, getting 2,2‐disubstitued pyrrolidines. Moreover, from some of the new 2,2‐disubstitued pyrrolidines were synthesized spiro‐pyrrolidines. J. Heterocyclic Chem.,(2011). 相似文献
133.
R Mello A Alcalde-Aragonés ME González Núñez G Asensio 《The Journal of organic chemistry》2012,77(15):6409-6413
Anhydrous [2-percarboxyethyl] functionalized silica (2a) is an advantageous oxidant for performing the epoxidation of olefins 1. Epoxides 3 do not undergo the ring-opening reactions catalyzed by the acidic silica surface, except for particularly activated cases such as styrene oxide. The hydrophilic and acidic character of the silica surface does not interfere with the directing effects exerted by allylic H-bond acceptor substituents. The alkenes 1 carrying hydroxyl groups react with silica-supported peracid 2a faster than unsubstituted alkenes, thus reversing the trend known for reactions with soluble peracids. These results are attributed to the H-bond interactions of substrate 1 with the silanol and carboxylic acid groups bonded to the silica surface. 相似文献
134.
Danuta Witkowska Rossella Politano Dr. Magdalena Rowinska‐Zyrek Prof. Remo Guerrini Prof. Maurizio Remelli Prof. Henryk Kozlowski 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(35):11088-11099
Hpn, one of Helicobacter pylori′s nickel‐accessory proteins, is an amazingly peculiar protein: Almost half of its sequence consists of polyhistidyl (poly‐His) residues. Herein, we try to understand the origin of this naturally occurring sequence, thereby shedding some light on the bioinorganic chemistry of Hpn′s numerous poly‐His repeats. By using potentiometric, mass spectrometric, and various spectroscopic techniques, we studied the NiII‐ and CuII complexes of the wild‐type Ac‐THHHHYHGG‐NH2 fragment of Hpn and of its six analogues, in which consecutive residues (His or Tyr) were replaced by Ala (Ala‐substitution or Ala‐scan approaches), thereby resulting in Ac‐TAHHHYHGG‐NH2, Ac‐THAHHYHGG‐NH2, Ac‐THHAHYHGG‐NH2, Ac‐THHHAYHGG‐NH2, Ac‐THHHHAHGG‐NH2, and Ac‐THHHHYAGG‐NH2 peptides. We found that the His4 residue is critical for both NiII‐ and CuII‐ion binding and the effectiveness of binding varies even if the substituted amino acid does not take part in the direct binding interactions. 相似文献
135.
Maria Michela Cesare Francesca Felice Veronica Conti Luca Cerri Ylenia Zambito Marco Romi Giampiero Cai Claudio Cantini Rossella Di Stefano 《Molecules (Basel, Switzerland)》2021,26(14)
Background: Tomato by-products contain a great variety of biologically active substances and represent a significant source of natural antioxidant supplements of the human diet. The aim of the work was to compare the antioxidant properties of a by-product from an ancient Tuscan tomato variety, Rosso di Pitigliano (RED), obtained by growing plants in normal conditions (-Ctr) or in drought stress conditions (-Ds) for their beneficial effects on vascular related dysfunction. Methods: The antioxidant activity and total polyphenol content (TPC) were measured. The identification of bioactive compounds of tomato peel was performed by HPLC. HUVEC were pre-treated with different TPC of RED-Ctr or RED-Ds, then stressed with H2O2. Cell viability, ROS production and CAT, SOD and GPx activities were evaluated. Permeation of antioxidant molecules contained in RED across excised rat intestine was also studied. Results: RED-Ds tomato peel extract possessed higher TPC than compared to RED-Ctr (361.32 ± 7.204 mg vs. 152.46 ± 1.568 mg GAE/100 g fresh weight). All extracts were non-cytotoxic. Two hour pre-treatment with 5 µg GAE/mL from RED-Ctr or RED-Ds showed protection from H2O2-induced oxidative stress and significantly reduced ROS production raising SOD and CAT activity (* p < 0.05 and ** p < 0.005 vs. H2O2, respectively). The permeation of antioxidant molecules contained in RED-Ctr or RED-Ds across excised rat intestine was high with non-significant difference between the two RED types (41.9 ± 9.6% vs. 26.6 ± 7.8%). Conclusions: RED-Ds tomato peel extract represents a good source of bioactive molecules, which protects HUVECs from oxidative stress at low concentration. 相似文献
136.
Zeineb Aturki Giovanni D’Orazio Salvatore Fanali Anna Rocco Federica Bortolotti Rossella Gottardo Franco Tagliaro 《Journal of chromatography. A》2009,1216(17):3652-3659
In this study, we present a capillary electrochromatographic method for separation of basic compounds of interest in forensic science (amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxymethamphetamine, 3,4-methylenedioxyethylamphetamine, cocaine, codeine, heroin, morphine, and 6-monoacethylmorphine). Several analytical conditions were taken into account to completely separate in the same run the 10 drugs of abuse analyzed. Chromatographic retention, selectivity and efficiency were evaluated in dependence of the type of stationary phase (CN and RP-C18 derivatized silica particles), mobile phase composition, buffer type and pH, sample injection. The optimum separation parameters were set up using a mixture of aqueous sodium phosphate buffer (pH 2.5)/acetonitrile (80/20, v/v) as the mobile phase, 10 kV and 20 °C as applied voltage and capillary temperature, respectively. Under these conditions all the studied analytes were baseline resolved within 20 min. The method performance was investigated in terms of precision, linearity, sensitivity and accuracy to demonstrate the applicability of the developed capillary electrochromatographic system to forensic analysis. Calibration curves provided a good linearity over a working range of 100–1200 ng/mL for all analytes. Limits of detection and quantification were in the range 5–12 ng/mL and 10–30 ng/mL, respectively. Then the method was applied to the analysis of a human urine sample spiked with a basic compounds’ mixture. Urine samples’ pre-treatment was carried out through a solid phase extraction (SPE) procedure on strong cation exchange (SCX) cartridges. 相似文献
137.
Rossella Agliardi 《Journal of Differential Equations》2002,180(1):89-98
In (R. Agliardi, 1995, Internat. J. Math.6, 791-804) we proved the well-posedness of the Cauchy problem in H∞ for some p-evolution equations (p?1) with real characteristic roots. For this purpose some assumptions on the lower order terms are needed, which, in the special case p=1, recapture well-known results for hyperbolic operators. In (R. Agliardi, 1995, Internat. J. Math.6, 791-804) the leading coefficients are assumed to be constant. In this paper we allow them to be variable. Our result is applicable to 2-evolution differential operators with real characteristics, i.e., to Schrödinger type operators. This class of operators comprehends, for example, Schrödinger operator Dt−Δx or the plate operator D2t−Δ2x. The Cauchy problem in H∞ for such evolution operators has been studied extensively by Takeuchi when the coefficients in the principal part are constant and the characteristic roots are distinct. 相似文献
138.
139.
140.
Summary In the retina of the turtle, prolonged illumination of the receptive field surrond can lead to the appearance of sustained
oscillatory responses in horizontal cells. In most cells the oscillations consist of a main component of 40–50 Hz frequency
modulated by slower waves. The experimental evidence suggests that these responses are due to the activation of the feeback
circuit linking cone photoreceptors and horizontal cells in the vertebrate retina.
Paper presented at the International Workshop ?Fluctuations in Physics and Biology: Stochastic Resonance, Signal Processing
and Related Phenomena?, Elba, 5–10 June 1994. 相似文献