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排序方式: 共有478条查询结果,搜索用时 15 毫秒
71.
Vitor Rosa Teresa Avilés Pedro T. Gomes Richard Welter M. Rosário Ribeiro 《Journal of organometallic chemistry》2008,693(4):769-775
A series of cobalt(II) compounds of the type [CoX2(α-diimine)] were synthesised by direct reaction of anhydrous CoCl2 or CoI2 and the corresponding α-diimine ligand, in CH2Cl2: [CoI2(o,o′,p-Me3C6H2-DAB)] (1), [CoI2(o,o′-iPr2C6H3-DAB)] (2), (where Ar-DAB = 1,4-bis(aryl)-2,3-dimethyl-1,4-diaza-1,3-butadiene), and [CoCl2(o,o′,p-Me3C6H2-BIAN)] (3), [CoCl2(o,o′-iPr2C6H3-BIAN)] (4), and [CoI2(o,o′-iPr2C6H3-BIAN)] (5) (where Ar-BIAN = bis(aryl)acenaphthenequinonediimine). All compounds were characterised by elemental analyses, IR, mass spectrometry, and X-ray diffraction whenever possible. The crystal structures of compounds 2-4 showed, in all cases, distorted tetrahedral geometries about the Co, built by two halogen atoms and two nitrogen atoms of the α-diimine ligand. Compounds 3 and 4, as well as [CoCl2(o,o′,p-Me3C6H2-DAB)] (1a), and [CoCl2(o,o′-iPr2C6H3-DAB)] (2a), were activated by methylaluminoxane (MAO) and tested as catalysts for ethylene polymerisation, showing low catalytic activities. Selected polyethylene (PE) samples were characterised by 1H and 13C NMR and FT-IR spectroscopies, and by differential scanning calorimetry (DSC), revealing branching microstructures (2.5-5.5%). 相似文献
72.
Caetano P. Sabino Martha S. Ribeiro Mark Wainwright Carolina dos Anjos Fábio P. Sellera Milena Dropa Nathalia B. Nunes Guilherme T. P. Brancini Gilberto U. L. Braga Victor E. Arana-Chavez Raul O. Freitas Nilton Lincopan Maurício S. Baptista 《Photochemistry and photobiology》2023,99(2):742-750
The unbridled dissemination of multidrug-resistant pathogens is a major threat to global health and urgently demands novel therapeutic alternatives. Antimicrobial photodynamic therapy (aPDT) has been developed as a promising approach to treat localized infections regardless of drug resistance profile or taxonomy. Even though this technique has been known for more than a century, discussions and speculations regarding the biochemical mechanisms of microbial inactivation have never reached a consensus on what is the primary cause of cell death. Since photochemically generated oxidants promote ubiquitous reactions with various biomolecules, researchers simply assumed that all cellular structures are equally damaged. In this study, biochemical, molecular, biological and advanced microscopy techniques were employed to investigate whether protein, membrane or DNA damage correlates better with dose-dependent microbial inactivation kinetics. We showed that although mild membrane permeabilization and late DNA damage occur, no correlation with inactivation kinetics was found. On the other hand, protein degradation was analyzed by three different methods and showed a dose-dependent trend that matches microbial inactivation kinetics. Our results provide a deeper mechanistic understanding of aPDT that can guide the scientific community toward the development of optimized photosensitizing drugs and also rationally propose synergistic combinations with antimicrobial chemotherapy. 相似文献
73.
Estrela RC Ribeiro FS Seixas BV Suarez-Kurtz G 《Rapid communications in mass spectrometry : RCM》2008,22(5):657-664
A method based on liquid-liquid extraction followed by high-performance liquid chromatography (HPLC) with positive ion electrospray ionization tandem mass spectrometry (ESI-MS/MS) detection was developed for the simultaneous determination of lopinavir (LPV) and ritonavir (RTV) in human blood, semen and saliva samples. The acquisition was performed in multiple reaction monitoring (MRM) mode, monitoring the transitions: m/z 629 > 447.1 for LPV, 721.18 > 268.02 for RTV and m/z 747.22 > 322.03 for the internal standard (IS). The limit of quantification was 1 ng/mL for both analytes in all matrices. The method was linear in the studied range (1-2000 ng/mL for LPV and 1-200 ng/mL for RTV), with r2 > 0.99 for each drug, and the run time was 4.5 min. The intra-assay precisions (%) were in the ranges of 0.1-14.2 (LPV) and 0.4-12.7 (RTV), the inter-assay precisions were in the ranges of 2.8-15.3 (LPV) and 1.1-12.8 (RTV) and the intra-and inter-assay recoveries were >85% for both drugs. The extraction efficiencies were 73.5-118.4% for LPV and 74.4-126.2% for RTV. The analytical method was applied to measure LPV and RTV concentrations in blood plasma (total and unbound fraction), saliva and semen of six HIV+ individuals under stable treatment with Kaletra soft gel capsules. The results were consistent with previously published data. 相似文献
74.
Viviane A.S. Falcomer Sebastião S. Lemos Guilherme B.C. Martins Gleison A. Casagrande Robert A. Burrow Ernesto S. Lang 《Polyhedron》2007
Complexes of general formula [CuL4][BF4] (L = benzonitrile – PhCN 2 or phenylacetonitrile – BzCN 3) have been prepared and structurally characterized by NMR spectroscopy and X-ray crystallography. Their structure and reactivity have been compared to the well known [Cu(MeCN)4][BF4] (1). The 63Cu line width and the 63Cu chemical shift have been evaluated by varying the temperature and the concentration of the complex 2 in benzonitrile solutions. The phenylacetonitrile solutions of the complex 3 give extremely broad signals which are beyond detection. Accordingly, compound 3 has been studied by 63Cu MAS NMR spectroscopy. The solution NMR data are consistent to the prevalence of dynamic equilibrium between tetra- and low-coordinated species in both complexes. The X-ray structure of 3 revealed that the copper(I) atom sits in a slightly distorted tetrahedral geometry, surrounded by four BzCN ligands. 相似文献
75.
We have explored the photochemical behavior of cationic triarylmethane dye monomers and dimers free in solution and noncovalently bound to bovine serum albumin (BSA) and examined how self-association and the formation of host-guest complexes involving biopolymers and photosensitizers affect the competition between the photosensitization type I and type II mechanisms. Our results have clearly indicated that tri-para-substituted triarylmethane dyes bind efficiently to albumin as monomers and dimers and, interestingly, that the formation of dye aggregates in aqueous solutions is actually assisted by the protein. Protein-assisted dye aggregation takes place under conditions of high biopolymer loading (high [dye]/[protein] ratios), as attested by the appearance of a hypsochromically shifted absorption band (H-band) that overlaps with the spectral shoulder of the respective dye monomer. As predicted by the molecular exciton theory, the intersystem crossing efficiency in H-type dimers is expected to be higher than in the respective dye monomers, and photoinduced electron transfer events are intrinsically favored in dye aggregates as a result of the physical contact between donor and acceptor. We have found that when triarylmethanes are noncovalently bound to BSA their photoreactivity undergoes a remarkable enhancement, and that the photooxidation mechanism type I is particularly favored in the macromolecular environment. A comparative examination of the behavior of triarylmethane dyes with that of methylene blue have shown that in the case of methylene blue the binding phenomenon also favor the type I mechanism. 相似文献
76.
77.
Guilherme G. Bessegato Michelle F. Brugnera Maria Valnice Boldrin Zanoni 《Current Opinion in Electrochemistry》2019
Color is an important element of the final product of many industries, including the textile, leather, food, cosmetic, pharmaceutical, plastic, and fuel-marking industries. Dyes are complex organic substances with chromophore and auxochromic groups, which can be electrochemically oxidized and/or reduced; this constitutes the basis of their electroanalytical determination. Despite some controversies, dyes pose risks to living organisms, especially after biotransformation, as the metabolites can be more toxic, mutagenic, or carcinogenic than the original dyes. The present work provides a brief overview of the recent progress in electrochemical sensors used for dye detection in diversified matrices. Sensors developed over the recent years are characterized by high sensitivity and selectivity, besides being economically advantageous once they allow the use of little or no clean-up samples in portable and miniaturized systems. 相似文献
78.
Lauro M. de Souza Thales R. CiprianiCarolina F. Sant’Ana Marcello IacominiPhilip A.J. Gorin Guilherme L. Sassaki 《Journal of chromatography. A》2009,1216(1):99-105
Two-dimensional liquid chromatography–electrospray ionization mass spectrometry was employed to analyze flavonol glycosides present in leaves of Maytenus ilicifolia, frequently used in traditional Brazilian medicine. Since they contain many flavonol glycosides, including isomers, one-dimensional liquid chromatography did not give complete separation and identification, yielding overlapping of compounds with different molecular weights. Thus, employing size exclusion chromatography in the first and reversed phase in the second dimension, a great number of flavonol glycosides could be identified and its relative abundances determined. The majority of glycosides contained kaempferol or quercetin as aglycones, and glycosides with previously unreported structures were also present and characterized. 相似文献
79.
80.
Beghidja A Rabu P Rogez G Welter R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(29):7627-7638
Carboxylate-bridged complexes of transition metals, M(II)=Mn(II), Fe(II), Co(II), Ni(II), Zn(II), were synthesised by reaction of M(II) salts with dl-malate and L-malate under hydrothermal conditions. These complexes form four series of compounds, which have been fully characterised structurally, thermally and magnetically. The crystal structures of the new chiral compounds, [Mn(L-mal)(H(2)O)] (1), [Fe(L-mal)(H(2)O)] (2), [Co(L-mal)(H(2)O)] (3) and [Zn(L-mal)(H(2)O)] (4) as well as those of the bimetallic analogues [Mn(0.63)Co(0.37)(L-mal)(H(2)O)] (5) and [Mn(0.79)Ni(0.21)(L-mal)(H(2)O)] (6) have been solved by single-crystal X-ray diffraction. The six L-malate monohydrates crystallise in the chiral space group P2(1)2(1)2(1) and consist in a three-dimensional network of metal(II) centres in octahedral sites formed by oxygen atoms. These structures were compared to those of the chiral trihydrate compounds [Co(L-mal)(H(2)O)]2 H(2)O (7), [Ni(L-mal)(H(2)O)]2 H(2)O (8) and [Co(0.52)Ni(0.48)(L-mal)(H(2)O)]2 H(2)O (9), which exhibit helical chains of M(II) centres, and those of dl-malate dihydrates [Co(dl-mal)(H(2)O)]H(2)O (10) and [Ni(dl-mal)(H(2)O)H(2)O (11) and trihydrate [Mn(L-mal)(H(2)O)]2 H(2)O (12) highlighting the great flexibility of the coordination by the malate ligand. UV/Vis spectroscopic results are consistent with octahedral coordination geometry of high-spin transition-metal centres. Extensive magnetic characterisation of each homologous series indicates rather weak coupling interaction between paramagnetic centres linked through carboxylate bridges. Curie-like paramagnetic, antiferromagnetic, ferromagnetic or weak ferromagnetic behaviour is observed and discussed on the basis of the structural features. The bimetallic compounds 5 and 6 represent new examples of chiral magnets. 相似文献