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排序方式: 共有182条查询结果,搜索用时 15 毫秒
21.
22.
Concetta?De?Stefano Antonio?GianguzzaEmail author Alberto?Pettignano Daniela?Piazzese Silvio?Sammartano 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(3):689-697
Stability data on the formation of dioxouranium(VI) species with polyacrylic (PAA) and fulvic acids (FA) are reported with
the aim to define quantitatively the sequestering capacity of these high molecular weight synthetic and naturally occurring
ligands toward uranium(VI), in aqueous solution. Investigations were carried out at t = 25 °C in NaCl medium at different ionic strengths and in absence of supporting electrolyte for uranyl–fulvate (
\textUO22+ {{\text{UO}}_{2}}^{2+} –FA) and uranyl–polyacrylate (
\textUO 2 2+ {{\text{UO}}_{ 2}}^{ 2+ } –PAA, PAA MW 2 kDa) systems, respectively. The experimental data are consistent with the following speciation models for the
two systems investigated: (i) UO2(FA1), UO2(FA1)(FA2), UO2(FA1)(FA2)(H) for
\textUO 2 2+ {{\text{UO}}_{ 2}}^{ 2+ } –fulvate (where FA1 and FA2 represent the carboxylic and phenolic fractions, respectively, both present in the structure of FA), and (ii) UO2(PAA), UO2(PAA)(OH), (UO2)2(PAA)(OH)2 for
\textUO 2 2+ {{\text{UO}}_{ 2}}^{ 2+ } –polyacrylate. By using the stability data obtained for all the complex species formed, the uranium(VI) sequestration by PAA
and FA was expressed by the pL50 parameter [i.e. the −log(total ligand concentration) necessary to bind 50% of uranyl ion] at different pH values. A comparison
between pL50 values of FA and PAA and some low molecular weight carboxylic ligands toward uranyl ion is also given. 相似文献
23.
Giuseppe Cremonesi Piero Dalla Croce Alessandra Forni Maddalena Gallanti Raffaella Gandolfi Concetta La Rosa 《Tetrahedron: Asymmetry》2009,20(16):1940-1947
Enantiomerically pure (5R)-(?)-5-phenyl-4,5-dihydroisoxazole-3-carboxylic acid ethyl ester was obtained via enzymatic resolution of the corresponding racemic mixture using a lipase from hog pancreas (PPL). The following reduction of the ester group to the corresponding alcohol and the oxidation of the latter led to (5R)-(?)-5-phenyl-4,5-dihydroisoxazole-3-carbaldehyde, and the reaction between this and Schöllkopf’s reagent, (2R)-(+)-2,5-dihydro-3,6-dimethoxy-2-isopropylpyrazine, gave mixtures of adducts with a good syn/anti ratio. The steric configurations of the major diastereoisomer were assigned on the basis of spectroscopic data and X-ray analysis. The subsequent controlled hydrolysis of the pyrazine ring led to β-(5-phenyl-4,5-dihydroisoxazol-3-yl)-serine methyl esters and the corresponding dipeptides with (R)-valine. Finally, reductive cleavage of the 4,5-dihydroisoxazole ring under hydrolytic conditions made it possible to obtain the corresponding polyfunctionalised dipeptides. 相似文献
24.
Domenico Grasso Salvatore Fasone Concetta Gandolfo Giuseppe Buemi 《Tetrahedron》1976,32(17):2105-2107
The validity of the equations reported by Amos and Burrows on solvent shifts has been tested in several solvents for seven different symmetrical compounds. The results confirm that their approximation introduced to simplify the interpretation of experimental data generally is not valid. 相似文献
25.
De Stefano C Milea D Porcino N Sammartano S 《Analytical and bioanalytical chemistry》2006,386(2):346-356
Interactions between myo-inositol 1,2,3,4,5,6-hexakis(dihydrogen phosphate) (phytic acid) and cadmium(II) were studied by using potentiometry (at
25 °C with the ISE-H+ glass electrode) in different metal to ligand (Phy) ratios (1:1≤Cd2+:Phy≤4:1) in NaClaq at different ionic strengths (0.1≤I/mol L−1≤1). Nine CdiHjPhy(12−2i−j)− species are formed with i=1 and 2 and 4≤j≤7; and trinuclear Cd3H4Phy2−. Dependence of complex formation constants on ionic strength was modeled by using Specific ion Interaction Theory (SIT) equations.
Phytate and cadmium speciation are also dependent on the metal to ligand ratio. Stability of CdiHjPhy(12−2i−j)− species was modeled as a function of both the ligand protonation step (j) and the number of metal cations bound to phytate
(i), and relationships found were used for the prediction of species other than those experimentally determined (mainly di-
and tri-protonated complexes), allowing the possibility of modeling Phy and Cd(II) behavior in natural waters and biological
fluids. A critical evaluation of phytate sequestering ability toward cadmium(II) has been made under several experimental
conditions, and the determination of an empirical parameter has been proposed for an objective “quantification” of this ability.
A thorough analysis of literature data on phytate–cadmium(II) complexes has been performed.
Previous contributions to this series: [1–8] 相似文献
26.
Maria Fernanda Taviano Emilia Cav Vivienne Spadaro Francesco Maria Raimondo Vincenzo Musolino Francesco Cacciola Yassine Oulad El Majdoub Luigi Mondello Concetta Condurso Fabrizio Cincotta Antonella Verzera Natalizia Miceli 《Molecules (Basel, Switzerland)》2021,26(14)
In a project designed to investigate the specific and infraspecific taxa of Matthiola endemic to Sicily (Italy) as new potential sources of bioactive compounds in this work, the infraspecific taxa of Matthiola fruticulosa were studied, namely, subsp. fruticulosa and subsp. coronopifolia. HPLC–PDA/ESI–MS and SPME–GC/MS analyses of hydroalcoholic extracts obtained from the aerial parts of the two subspecies led to the detection of 51 phenolics and 61 volatile components, highlighting a quite different qualitative–quantitative profile. The antioxidant properties of the extracts were explored through in vitro methods: 1,1-diphenyl-2-picrylhydrazyl (DPPH), reducing power and Fe2+ chelating activity assays. The results of the antioxidant tests showed that the extracts possess a different antioxidant ability: particularly, the extract of M. fruticulosa subsp. fruticulosa exhibited higher radical scavenging activity than that of subsp. coronopifolia (IC50 = 1.25 ± 0.02 mg/mL and 2.86 ± 0.05 mg/mL), which in turn displayed better chelating properties (IC50 = 1.49 ± 0.01 mg/mL and 0.63 ± 0.01 mg/mL). Lastly, Artemia salina lethality bioassay was performed for toxicity assessment. The results of the bioassay showed lack of toxicity against brine shrimp larvae for both extracts. The data presented indicate the infraspecific taxa of M. fruticulosa as new and safe sources of antioxidant compounds. 相似文献
27.
Concetta Cafiero Agnese Re Egidio Stigliano Ezio Bassotti Rossana Moroni Cristina Grippaudo 《Electrophoresis》2019,40(14):1820-1823
Efficient DNA extraction procedures is a critical step involved in the process of successful DNA analysis of such samples. Various protocols have been devised for the genomic DNA extraction from human tissues and forensic stains, such as dental tissue that is the skeletal part that better preserves DNA over time. However DNA recovery is low and protocols require labor‐intensive and time‐consuming step prior to isolating genetic material. Herein, we describe an extremely fast procedure of DNA extraction from teeth compared to classical method. Sixteen teeth of 100‐year‐old human remains were divided into two groups of 8 teeth and we compared DNA yield, in term of quantity and quality, starting from two different sample preparation steps. Specifically, teeth of group 1 were treated with a classic technique based on several steps of pulverization and decalcification, while teeth of group 2 were processed following a new procedure to withdraw dental pulp. In the next phase, the samples of both group underwent the same procedure of extraction, quantification and DNA profile analysis. Our findings provide an alternative protocol to obtain a higher amount of good quality DNA in a fast time procedure, helpful for forensic and anthropological studies. 相似文献
28.
A fast ion chromatographic method with suppressed conductivity detection has been developed for the simultaneous determination of methane-, ethane-, 1-propane-, 1-butane-, 1-pentane-, 1-hexane-, 1-heptane-, 1-octane-, 1-nonane-, 1-decane-, 1-dodecane-, dodecylbenzene-, p-toluene-, benzenesulfonic acids, octylsulfate and dodecylsulfate in water samples. Due to the high number of analytes and their heterogeneity, the effect of the mobile phase parameters (NaOH, CH(3)OH and CH(3)CN concentration) on the retention factors has been studied in detail, so achieving, for the first time, the separation among 15 of these analytes by a gradient elution. Detection limits included within 0.06-0.16 microM have been obtained. Interferences from Cl(-), NO(3)(-) and SO(4)(2-), possible anions present in water samples, have been considered and a SPE procedure has been developed for analytes enrichment and matrix removal in a seawater sample. This is the first application of an ion-exchange chromatographic method to a seawater sample for this kind of analytes. 相似文献
29.
High performance ion chromatography of haloacetic acids on macrocyclic cryptand anion exchanger 总被引:1,自引:0,他引:1
Bruzzoniti MC De Carlo RM Horvath K Perrachon D Prelle A Tófalvi R Sarzanini C Hajós P 《Journal of chromatography. A》2008,1187(1-2):188-196
A new high performance ion chromatographic method has been developed for the separation of the nine chlorinated-brominated haloacetic acids (HAAs) that are the disinfection by-products of chlorination of drinking water, using a macrocycle-based adjustable-capacity anion-exchange separator column (IonPac Cryptand A1). A gradient method based on theoretical and experimental considerations has been optimized in which 10 mM NaOH-LiOH step gradient was performed at the third minute of the analysis. The optimized method allowed us to separate the nine HAAs and seven possibly interfering inorganic anions in less than 25 min with acceptable resolution. The minimum concentrations detectable for HAAs were between 8.0 (MBA) and 210 (TBA) microg L(-1), with linearity included between 0.9947 (TBA) and 0.9998 (MBA). To increase sensitivity, a 25-fold preconcentration step on a reversed phase substrate (LiChrolut EN) has been coupled. Application of this method to the analysis of haloacetic acids in real tap water samples is illustrated. 相似文献
30.
Costantino V Fattorusso E Imperatore C Mangoni A 《The Journal of organic chemistry》2008,73(16):6158-6165
Reinvestigation of the glycosphingolipid composition of the marine sponge Spheciospongia vesparia revealed the presence of vesparioside B ( 2a), a new furanose-rich hexaglycosylated glycosphingolipid that is the most complex glycosphingolipid isolated from a marine sponge to date. The structure of the new compound was elucidated using extensive 2D NMR studies and chemical degradation. Particularly useful for structure elucidation of vesparioside B was a quantum mechanical computational study, showing that in furanosides a vicinal coupling constant <2.0 Hz (for H-1/H-2 or H-3/H-4) or <3.5 Hz (for H-2/H-3) is a proof of the trans orientation of the relevant protons. This general rule, combined with ROE data, allowed us to elucidate the relative stereochemistry (including anomeric configuration) of the three furanose five-membered rings. 相似文献