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排序方式: 共有116条查询结果,搜索用时 203 毫秒
1.
2.
A method for the simultaneous spectrophotometric determination of the divalent ions of iron, cobalt, nickel and copper based on the formation of their complexes with 1,5-bis(di-2-pyridylmethylene) thiocarbonohydrazide (DPTH) is proposed. The resolution of quaternary mixtures of these metallic ions was accomplished by several chemometric approaches. A comparative study of the results obtained for simultaneous determinations in mixture by using principal component regression (PCR) and partial least-squares regression (PLS-1 and PLS-2) for absorbance, first-derivative and second-derivative data is presented. In general, the best recovery values are obtained by the PLS-2 method for absorbance data. This procedure allows the simultaneous determination of the cited ions in alloys and biological materials Good reliability of the determination was proved. 相似文献
3.
A method for the simultaneous spectrophotometric determination of cadmium, copper and zinc based on the formation of their complexes with 1,5-bis(di-2-pyridylmethylene)thiocarbonohydrazide is proposed. The absorption curves of these complexes overlap severely in the scanning range 380–480 nm. The analyte concentrations are calculated by a least squares fit of the pure spectra to the mixture spectra. A linear determination range of 0.1–1.7 μg/ml for cadmium, 0.1–1.3 μg/ml for copper and 0.2–1.2 μg/ml for zinc were obtained. The effect of interference was studied. The method has been applied to the determination of these metal ions in various type of materials. 相似文献
4.
M. Eugenia Pérez‐Ojeda Dr. Beatriz Trastoy Álvaro Rol Dr. María D. Chiara Prof. Dr. Inmaculada García‐Moreno Dr. Jose Luis Chiara 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(21):6630-6640
A general procedure for the assembly of hetero‐bifunctional cubic silsesquioxanes with diverse functionality and a perfectly controlled distribution of functional groups on the inorganic framework has been developed. The method is based on a two‐step sequence of mono‐ and hepta‐functionalization through the ligand‐accelerated copper(I)‐catalyzed azide–alkyne cycloaddition of a readily available octaazido cubic silsesquioxane. The stoichiometry of the reactants and the law of binomial distribution essentially determine the selectivity of the key monofunctionalization reaction when a copper catalyst with strong donor ligands is used. The methodology has been applied to the preparation of a set of bifunctional nano‐building‐blocks with orthogonal reactivity for the controlled assembly of precisely defined hybrid nanomaterials and a fluorescent multivalent probe for application in targeted cell‐imaging. The inorganic cage provides an improved photostability to the covalently attached dye as well as a convenient framework for the 3D multivalent display of the pendant epitopes. Thus, fluorescent bioprobes based on well‐defined cubic silsesquioxanes offer interesting advantages over more conventional fully organic analogues and ill‐defined hybrid nanoparticles and promise to become powerful tools for the study of cell biology and for biomedical applications. 相似文献
5.
Racemic and Quasi‐Racemic X‐ray Structures of Cyclic Disulfide‐Rich Peptide Drug Scaffolds 下载免费PDF全文
Conan K. Wang Gordon J. King Susan E. Northfield Paola G. Ojeda Prof. Dr. David J. Craik 《Angewandte Chemie (International ed. in English)》2014,53(42):11236-11241
Cyclic disulfide‐rich peptides have exceptional stability and are promising frameworks for drug design. We were interested in obtaining X‐ray structures of these peptides to assist in drug design applications, but disulfide‐rich peptides can be notoriously difficult to crystallize. To overcome this limitation, we chemically synthesized the L ‐ and D ‐forms of three prototypic cyclic disulfide‐rich peptides: SFTI‐1 (14‐mer with one disulfide bond), cVc1.1 (22‐mer with two disulfide bonds), and kB1 (29‐mer with three disulfide bonds) for racemic crystallization studies. Facile crystal formation occurred from a racemic mixture of each peptide, giving structures solved at resolutions from 1.25 Å to 1.9 Å. Additionally, we obtained the quasi‐racemic structures of two mutants of kB1, [G6A]kB1, and [V25A]kB1, which were solved at a resolution of 1.25 Å and 2.3 Å, respectively. The racemic crystallography approach appears to have broad utility in the structural biology of cyclic peptides. 相似文献
6.
Dispersive liquid?Cliquid microextraction (DLLME) is a relatively novel miniaturized sample pre-treatment technique. DLLME has been applied for the analysis of a large variety of organic compounds and metal ions in different samples. This paper reviews the more recent applications of this procedure for sample preparation. 相似文献
7.
After establishing bounds on the Rao function and on the genus of projective curves that generalize the ones in [5] and in [12], we describe the even G-liaison classes of some unions of curves attaining the bounds, and of more general unions with analogous geometric properties. In particular, we prove that their Hartshorne-Rao module identifies the even G-liaison class. 相似文献
8.
In the present paper, we have synthesized a biomorphic ceramic material from oak wood as biological template structure and infiltration with zirconia-sol. After the material characterization, we have optimized the sample dissolution by acid attack in an oven under microwave irradiation. Experimental designs were used as a multivariate strategy for the effect's evaluation of varying several variables. This article describes the development by response surface methodology (RSM) of a procedure for zirconium determination, and other ions, such as copper and nickel by inductively coupled plasma mass spectrometry (ICP-MS) and others, such as iron, calcium and magnesium determination by flame atomic absorption spectrometry (FAAS) in the synthesized sample after digestion. A full factorial design (33) was used to find optimal conditions for the procedure through response surface study. Three variables (time, HNO3 volume and HF volume) were regarded as factors and as response to the concentration of different metal ions in the optimization study. 相似文献
9.
L. Funke J. Döring P. Kemnitz P. Ojeda R. Schwengner E. Will G. Winter A. Johnson L. Hildingsson Th. Lindblad 《Zeitschrift für Physik A Hadrons and Nuclei》1986,323(2):127-137
Projectile and targetK-vacancy production probabilities in 4.6-, 5.8- and 7.3-MeV/a.m.u. U+U and U+Pb collisions are reported for impact parameters between 10 and 85 fm. These probability measurements are compared with available theory. 相似文献
10.
Maribel Navarro Clara Hernández Flor Vásquez Helen Goitia Luis E. Ojeda Mait Velásquez Germán Fraile 《Transition Metal Chemistry》2008,33(7):893-898
Antimalarial drugs such as chloroquine are beneficial agents in systemic lupus and rheumatoid arthritis. In this work, two
new chloroquine diphosphate (CQDP) complexes containing Zn(II) and Au(III) of formula Zn(CQDP)(NO3)2 (1) and Au(CQDP)Cl3 (2), respectively, were synthesized and characterized by physico-chemical and spectroscopic methods. To examine their possible
anti-inflammatory properties, the new derivatives were tested in the range from 1 to 100 μM on the respiratory burst of isolated
human neutrophils (PMNs) as well as in whole blood. In isolated PMNs, complex 1 inhibited the isoluminol-enhanced chemiluminescence (IL-CL) only at the highest concentration tested, whereas in the whole
blood assay, 10 μM of this complex was sufficient to significantly inhibit the luminol-enhanced chemiluminescence (L-CL).
On the contrary, complex 2 dose-dependently inhibited the IL-CL but affected the L-CL only at 100 μM. In conclusion, both complexes are more active
than CQDP and may be useful for future treatment of diseases resulting from exacerbated neutrophil functions. 相似文献