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741.
Stefania Pragliola Chiara Costabile Francesca Di Bartolomeo Pasquale Longo 《Macromolecular rapid communications》2004,25(10):995-999
Summary: Copolymerizations of propene and buta‐1,3‐diene performed in the presence of rac‐[CH2(3‐tert‐butyl‐1‐indenyl)2]ZrCl2 and methylaluminoxane (MAO) have been investigated. Buta‐1,3‐diene gives prevailingly primary coordination to the metal, producing overall 1,2 units. Cyclopropane and cyclopentane rings, although in low amounts, are also obtained. The presence of butadiene would be responsible for some regioirregular 2,1‐inserted propene units, which at high temperatures give rearrangement to 3,1 units.
742.
The aim of this study was to evaluate the chromatographic performance of a PEG stationary phase, in comparison with those of C18 columns, for the HPLC analysis of phenethylamine ((+/-)-synephrine) and indoloquinazoline (rutaecarpine and evodiamine) alkaloids in methanolic extracts of fruits of Evodia rutaecarpa (Juss.) Benth. and E. rutaecarpa (Juss.) Benth. var. officinalis (Dode) Huang (i.e., E. officinalis Dode) (Rutaceae family). The method was validated and showed good linearity, precision, accuracy, sensitivity, and specificity. The highest content of both phenethylamine and indoloquinazoline alkaloids was found in methanolic fruit extracts of E. rutaecarpa, and it was closely related to the degree of maturity. E. officinalis fruits displayed low amounts of both types of alkaloids. Furthermore, an enantioselective HPLC method for the enantioseparation of (+/-)-synephrine from Evodia fruits was applied, by using a protein-based chiral stationary phase with cellobiohydrolase (CBH) as the chiral selector (Chiral-CBH). Isolation of synephrine from Evodia aqueous fruit extracts was carried out by strong cation-exchange SPE. The results of the application of the method to the analysis of Evodia samples showed that (-)-synephrine was the main component while (+)-synephrine was present in low concentration. 相似文献
743.
Stefania Pragliola Chiara Costabile Mariagrazia Napoli Gaetano Guerra Pasquale Longo 《Macromolecular Symposia》2006,234(1):128-138
Olefin-diene copolymerizations in the presence of C2 symmetric zirconocene rac-[CH2(3-tert-butyl-1-indenyl)2]ZrCl2/MAO catalytic system have been reported and rationalized by experimental and molecular modeling studies. Ethene gives 1,2-cyclopropane and 1,2-cyclopentane, 1,3-cyclobutane, and 1,3-cyclopentane units in copolymerization with 1,3-butadiene, 1,4-pentadiene, and 1,5-hexadiene, respectively. Propene-1,3-butadiene copolymerizations lead to 1,2 and 1,4 butadiene units and to a low amount of 1,2-cyclopropane units. 相似文献
744.
Dieter Seebach Estelle Dubost Raveendra I. Mathad Bernhard Jaun Michael Limbach Markus Löweneck Oliver Flögel James Gardiner Stefania Capone Albert K. Beck Hans Widmer Daniel Langenegger Dominique Monna Daniel Hoyer 《Helvetica chimica acta》2008,91(9):1736-1786
Cyclo‐β‐tetrapeptides are known to adopt a conformation with an intramolecular transannular hydrogen bond in solution. Analysis of this structure reveals that incorporation of a β2‐amino‐acid residue should lead to mimics of ‘α‐peptidic β‐turns’ (cf. A, B, C ). It is also known that short‐chain mixed β/α‐peptides with appropriate side chains can be used to mimic interactions between α‐peptidic hairpin turns and G protein‐coupled receptors. Based on these facts, we have now prepared a number of cyclic and open‐chain tetrapeptides, 7 – 20 , consisting of α‐, β2‐, and β3‐amino‐acid residues, which bear the side chains of Trp and Lys, and possess backbone configurations such that they should be capable of mimicking somatostatin in its affinity for the human SRIF receptors (hsst1–5). All peptides were prepared by solid‐phase coupling by the Fmoc strategy. For the cyclic peptides, the three‐dimensional orthogonal methodology (Scheme 3) was employed with best success. The new compounds were characterized by high‐resolution mass spectrometry, NMR and CD spectroscopy, and, in five cases, by a full NMR‐solution‐structure determination (in MeOH or H2O; Fig. 4). The affinities of the new compounds for the receptors hsst1–5 were determined by competition with [125I]LTT‐SRIF28 or [125I] [Tyr10]‐CST14. In Table 1, the data are listed, together with corresponding values of all β‐ and γ‐peptidic somatostatin/Sandostatin® mimics measured previously by our groups. Submicromolar affinities have been achieved for most of the human SRIF receptors hsst1–5. Especially high, specific binding affinities for receptor hsst4 (which is highly expressed in lung and brain tissue, although still of unknown function!) was observed with some of the β‐peptidic mimics. In view of the fact that numerous peptide‐activated G protein‐coupled receptors (GPCRs) recognize ligands with turn structure (Table 2), the results reported herein are relevant far beyond the realm of somatostatin: many other peptide GPCRs should be ‘reached’ with β‐ and γ‐peptidic mimics as well, and these compounds are proteolytically and metabolically stable, and do not need to be cell‐penetrating for this purpose (Fig. 5). 相似文献
745.
Daniela Coppola Stefano Bruno Luca Ronda Cristiano Viappiani Stefania Abbruzzetti Guido di Prisco Cinzia Verde Andrea Mozzarelli 《BMC biochemistry》2011,12(1):1-8
Background
The majority of peroxisomal matrix proteins destined for translocation into the peroxisomal lumen are recognised via a C-terminal Peroxisomal Target Signal type 1 by the cycling receptor Pex5p. The only structure to date of Pex5p in complex with a cargo protein is that of the C-terminal cargo-binding domain of the receptor with sterol carrier protein 2, a small, model peroxisomal protein. In this study, we have tested the contribution of a second, ancillary receptor-cargo binding site, which was found in addition to the characterised Peroxisomal Target Signal type 1.Results
To investigate the function of this secondary interface we have mutated two key residues from the ancillary binding site and analyzed the level of binding first by a yeast-two-hybrid assay, followed by quantitative measurement of the binding affinity and kinetics of purified protein components and finally, by in vivo measurements, to determine translocation capability. While a moderate but significant reduction of the interaction was found in binding assays, we were not able to measure any significant defects in vivo.Conclusions
Our data therefore suggest that at least in the case of sterol carrier protein 2 the contribution of the second binding site is not essential for peroxisomal import. At this stage, however, we cannot rule out that other cargo proteins may require this ancillary binding site. 相似文献746.
747.
Novel Composite Plastics Containing Silver(I) Acylpyrazolonato Additives Display Potent Antimicrobial Activity by Contact 下载免费PDF全文
Prof. Fabio Marchetti Dr. Jessica Palmucci Prof. Claudio Pettinari Dr. Riccardo Pettinari Dr. Francesca Condello Dr. Stefano Ferraro Dr. Mirko Marangoni Prof. Alessandra Crispini Dr. Stefania Scuri Prof. Iolanda Grappasonni Prof. Mario Cocchioni Dr. Massimo Nabissi Dr. Michele R. Chierotti Prof. Roberto Gobetto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(2):836-850
New silver(I) acylpyrazolonato derivatives displaying a mononuclear, polynuclear, or ionic nature, as a function of the ancillary azole ligands used in the synthesis, have been fully characterized by thermal analysis, solution NMR spectroscopy, solid‐state IR and NMR spectroscopies, and X‐ray diffraction techniques. These derivatives have been embedded in polyethylene (PE) matrix, and the antimicrobial activity of the composite materials has been tested against three bacterial strains (E. coli, P. aeruginosa, and S. aureus): Most of the composites show antimicrobial action comparable to PE embedded with AgNO3. Tests by contact and release tests for specific migration of silver from PE composites clearly indicate that, at least in the case of the PE, for composites containing polynuclear silver(I) additives, the antimicrobial action is exerted by contact, without release of silver ions. Moreover, PE composites can be re‐used several times, displaying the same antimicrobial activity. Membrane permeabilization studies and induced reactive oxygen species (ROS) generation tests confirm the disorganization of bacterial cell membranes. The cytotoxic effect, evaluated in CD34+ cells by MTT (3‐(4,5‐dimethylthiazole‐2‐yl)‐2,5‐diphenyltetrazoliumbromide) and CFU (colony forming units) assays, indicates that the PE composites do not induce cytotoxicity in human cells. Studies of ecotoxicity, based on the test of Daphnia magna, confirm tolerability of the PE composites by higher organisms and exclude the release of Ag+ ions in sufficient amounts to affect water environment. 相似文献
748.
Daniele D'Alonzo Dr. Arthur Van Aerschot Prof. Dr. Annalisa Guaragna Dr. Giovanni Palumbo Prof. Guy Schepers Stefania Capone Dr. Jef Rozenski Prof. Dr. Piet Herdewijn Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(39):10121-10131
Oligonucleotides composed of 1′,5′‐anhydro‐arabino‐hexitol nucleosides belonging to the L series (L ‐HNA) were prepared and preliminarily studied as a novel potential base‐pairing system. Synthesis of enantiopure L ‐hexitol nucleotide monomers equipped with a 2′‐(N6‐benzoyladenin‐9‐yl) or a 2′‐(thymin‐1‐yl) moiety was carried out by a de novo approach based on a domino reaction as key step. The L oligonucleotide analogues were evaluated in duplex formation with natural complements as well as with unnatural sugar‐modified oligonucleotides. In many cases stable homo‐ and heterochiral associations were found. Besides Tm measurements, detection of heterochiral complexes was unambiguously confirmed by LC‐MS studies. Interestingly, circular dichroism measurements of the most stable duplexes suggested that L ‐HNA form left‐handed helices with both D and L oligonucleotides. 相似文献
749.
Ana Carolina Corrêa Eliangela de Morais Teixeira Vitor Brait Carmona Kelcilene Bruna Ricardo Teodoro Cauê Ribeiro Luiz Henrique Capparelli Mattoso José Manoel Marconcini 《Cellulose (London, England)》2014,21(1):311-322
Nanocomposites of polyamides with cellulose whiskers are difficult to obtain by conventional processing of extrusion and injection molding because of the low thermal stability of the cellulosic nanostructures and the relatively high processing temperature of polyamides, which is higher than the temperature of thermal degradation of cellulose whiskers. Thus, in this study cellulose whiskers were coated with polyamide 6 (PA6) in order to increase their thermal stability and prevent the formation of agglomerates. This coating on cellulose whiskers allows their application to obtain nanocomposites with polyamides, whose processing temperatures are relatively high, around 250 °C. Cellulose whiskers (CWs) were obtained from cotton fibers by acid hydrolysis. The freeze-dried CWs were coated with PA6 by dispersing them in formic acid; PA6 was solubilized in this suspension. The cellulose-coated whiskers (CCWs) were characterized by X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetry (TG), scanning electron microscopy (SEM-FEG) and infrared spectroscopy. SEM-FEG and TG results showed that the PA6 coating on CWs prevented high agglomeration of dried CWs and promoted an increase in their thermal stability from 180 to 280 °C, allowing the use of CCWs to obtain nanocomposites with PA6 using conventional processing routes, such as extrusion and injection molding, at appropriate processing temperatures. In this way, 1 wt% CCWs was used to prepare nanocomposites with PA6. The PA6 + 1CW nanocomposites were compared to neat PA6 without CWs. The samples were characterized by tensile tests and DSC, and the results showed that the PA6 coating on CWs was effective in raising the thermal stability of CWs, improving the dispersion of CWs in the matrix of PA6, resulting in a 45 % increase in the elastic modulus of the nanocomposite with only 1 wt% of coated cellulose whiskers in comparison to neat PA6. 相似文献
750.
A Quantitative Relaxometric Version of the ELISA Test for the Measurement of Cell Surface Biomarkers 下载免费PDF全文
Dr. Diego Alberti Dr. Mark van't Erve Dr. Rachele Stefania Dr. Maria Rosaria Ruggiero Dr. Marta Tapparo Dr. Simonetta Geninatti Crich Prof. Silvio Aime 《Angewandte Chemie (International ed. in English)》2014,53(13):3488-3491
Quantitative measurement of marker expression in diseased cells is still a topic of considerable interest and different methodologies are currently under intense scrutiny. This work aims at developing an in vitro diagnostic method based on the release of paramagnetic species from relaxometrically “silent” liposomes operated by the action of a phospholipase A2 (PLA2) previously targeted to the epitope of interest. The released paramagnetic species causes an increase of the longitudinal water proton relaxation rate proportional to the number of PLA2 bound to the cell outer surface. The sensitivity of the herein proposed method, named R‐ELISA, was attempted in the detection of folate receptor expression on human ovarian cancer cells by functionalizing PLA2 with folic acid. Receptor/cell number of 8.3×105 has been measured on IGROV‐1 cells. The R‐ELISA assay can detect nanomolar cell suspension receptor concentrations and has been validated by well‐established spectrofluorimetric procedures. 相似文献