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991.
Marisa Freitas 《Analytica chimica acta》2009,649(1):8-8272
Neutrophils, also known as polymorphonuclear leukocytes (PMN), are the most common type of white blood cells, comprising about 50-70% of all white blood cells. In the event of inflammatory processes, neutrophils display increased mobility, tissue influx ability, prolonged life span, and an increased phagocytic capacity, constituting the initial participants in the cellular defense of the organism. One of the most important defense systems of neutrophils corresponds to their ability to mediate a strong oxidative burst through the formation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). While oxidative burst is important for the elimination of invading microorganisms, the overproduction of ROS and RNS or the impairment of endogenous antioxidant defenses may result to detrimental effects to the host. The nature and the extent of ROS and RNS production by neutrophils in response to different stimuli is, consequently, a matter of extensive research, with scientific reports showing an enormous variability on the detection methodologies employed. This review attempts to provide a critical assessment of the most common approaches to identify and quantify reactive species formed during the neutrophils’ oxidative burst. The detection mechanisms and performance, as well as advantages and limitations of the different methodologies, are scrutinized, focusing on the use of fluorimetric, chemiluminometric and colorimetric probes. 相似文献
992.
An overview of analytical methodologies for the determination of antibiotics in environmental waters 总被引:3,自引:0,他引:3
The widespread occurrence of antibiotics as contaminants in the aquatic environment has increased attention in the last years. The concern over the release of antibiotics into the environment is related primarily to the potential for the development of antimicrobial resistance among microorganisms. This article presents an overview of analytical methodologies for the determination of quinolone (Qs) and fluoroquinolone (FQs), macrolide (MLs), tetracycline (TCs), sulfonamide (SAs) antibiotics and trimethoprim (TMP) in different environmental waters. The analysis of these antibiotics has usually been carried out by high-performance liquid chromatography (HPLC) coupled to mass spectrometry (MS) or tandem mass spectrometry (MS/MS) and to a lesser extent by ultraviolet (UV) or fluorescence detection (FD). A very important step before LC analysis is sample preparation and extraction leading to elimination of interferences and prevention of matrix effect and preconcentration of target analytes. 相似文献
993.
Pu Su Zhao Rong Qing Li Xiao Jun Sun Huan Mei Guo Fang Fang Jian 《Structural chemistry》2009,20(3):443-451
Two 2-pyrazoline derivatives of 1-phenyl-3-(4-chlorophenyl)-5-(2-chlorophenyl)-2-pyrazoline (1) and 1-phenyl-3-(4-methylphenyl)-5-(2-chlorophenyl)-2-pyrazoline (2) have been synthesized and characterized by elemental analysis, IR, UV–Vis, and fluorescence spectra. The crystal structure
of 2 has been determined by X-ray single crystal diffraction. For the two compounds, density functional theory (DFT) calculations
of the structures and natural population atomic charge analysis have been performed at B3LYP/6-311G** level of theory. By
using TD-DFT method, electron spectra of 1 and 2 have been predicted, which are in good agreement with the experimental ones. Comparative studies on 1 and 2 indicate that the change of substituted groups in 3-phenyl ring of pyrazoline ring will change the peak intensity and peak
locations both in electron spectra and fluorescence spectra. 相似文献
994.
Yan Lee Dr. Takehiko Ishii Dr. Horacio Cabral Dr. Hyun Jin Kim Ji‐Hun Seo Nobuhiro Nishiyama Dr. Hiroki Oshima Kensuke Osada Dr. Kazunori Kataoka Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(29):5309-5312
Special delivery! Polyionic complex (PIC) micelles that contain the charge‐conversional moieties citaconic amide or cis‐aconitic amide were developed for cytoplasmic protein delivery. The increase of the charge density on the protein cargo helped the stability of the PIC micelles without cross‐linking, and the charge‐conversion in endosomes induced the dissociation of the PIC micelles to result in efficient endosomal release (see picture).
995.
Herbert Meier Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(22):3911-3913
En route to molecular electronics : As extended, conjugated oligomers are desirable for molecular electronics, their electrical conductance should display a low attenuation factor. Zinc‐complexed oligo(ethynyleneporphyrindiylethynylene)s have been prepared that are distinguished by ultralow attenuation factors in single‐molecule conductance.
996.
Shanmugam Easwaramoorthi Dr. Jae‐Yoon Shin Sung Cho Dr. Pyosang Kim Yasuhide Inokuma Eiji Tsurumaki Atsuhiro Osuka Prof. Dr. Dongho Kim Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(44):12005-12017
Donor–acceptor systems based on subporphyrins with nitro and amino substituents at meta and para positions of the meso‐phenyl groups were synthesized and their photophysical properties have been systematically investigated. These molecules show two types of charge‐transfer interactions, that is, from center to periphery and periphery to center depending on the peripheral substitution, in which the subporphyrin moiety plays a dual role as both donor and acceptor. Based on the solvent‐polarity‐dependent photophysical properties, we have shown that the fluorescence emission of para isomers originates from the solvatochromic, dipolar, symmetry‐broken, and relaxed excited states, whereas the non‐solvatochromic fluorescence of meta isomers is of the octupolar type with false symmetry breaking. The restricted meso‐(4‐aminophenyl) rotation at low temperature prevents the intramolecular charge‐transfer (ICT)‐forming process. The two‐photon absorption (TPA) cross‐section values were determined by photoexcitation at 800 nm in nonpolar toluene and polar acetonitrile solvents to see the effect of ICT on the TPA processes. The large enhancement in the TPA cross‐section value of approximately 3200 GM (1 GM=10?50 cm4 s photon?1) with donor–acceptor substitution has been attributed to the octupolar effect and ICT interactions. A correlation was found between the electron‐donating/‐withdrawing abilities of the peripheral groups and the TPA cross‐section values, that is, p‐aminophenyl>m‐aminophenyl>nitrophenyl. The increased stability of octupolar ICT interactions in highly polar solvents enhances the TPA cross‐section value by a factor of approximately 2 and 4, respectively, for p‐amino‐ and m‐nitrophenyl‐substituted subporphyrins. On the other hand, the stabilization of the symmetry‐broken, dipolar ICT state gives rise to a negligible impact on the TPA processes. 相似文献
997.
Christophe Aronica Dr. Anna Venancio‐Marques Jérôme Chauvin Dr. Vincent Robert Dr. Gilles Lemercier Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(20):5047-5055
Finely tuned optical properties : The optical properties of substituted protected catechol derivatives can be fine‐tuned (see scheme; TBDMS=tert‐butyldimethylsilyloxy). The DFT‐calculated polarisabilities are compared with experimental data.
998.
Maj‐Britt Suhr Kirketerp Michael Åxman Petersen Dr. Marius Wanko Dr. Leonardo Andres Espinosa Leal Henning Zettergren Dr. Françisco M. Raymo Prof. Angel Rubio Prof. Mogens Brøndsted Nielsen Prof. Steen Brøndsted Nielsen Prof. 《Chemphyschem》2009,10(8):1207-1209
From blue to red: While four π‐conjugated nitrophenolates absorb within a relatively narrow region in solution, they cover the entire visible spectrum when isolated in vacuo (see picture). The work combines gas‐ and solution‐phase spectroscopy and provides the first benchmark of theoretical excitation energies for nitrophenolates.
999.
Philipp Zacharias Dr. Malte C. Gather Dr. Anne Köhnen Dr. Nina Rehmann Klaus Meerholz Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(22):3883-3883
Programmable organic light‐emitting diodes: UV irradiation converts an oxetane‐functionalized dithienylethene derivative from its colorless open form into a dark blue closed form, while visible light reverses the reaction. In the Communication on page 4038 ff., K. Meerholz and co‐workers describe a reversibly switchable organic light‐emitting diode based on this principle.
1000.
Kai Huang Dr. Florence Duclairoir Dr. Tiziana Pro Dr. Julien Buckley Dr. Gilles Marchand Dr. Eugénie Martinez Dr. Jean‐Claude Marchon Dr. Barbara De Salvo Dr. Guillaume Delapierre Dr. Françoise Vinet Dr. 《Chemphyschem》2009,10(6):963-971
The missing link : Ferrocene and porphyrin monolayers are tethered on silicon surfaces with short (see picture, left) or long (right) linkers. Electron transfer to the silicon substrate is faster for monolayers with a short linker.