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991.
Farias PM Santos BS Thomaz AA Ferreira R Menezes FD Cesar CL Fontes A 《The journal of physical chemistry. B》2008,112(9):2734-2737
In this work we used a setup consisting of an optical tweezers combined with a nonlinear microspectroscopy system to perform scanning microscopy and obtain emission spectra using two photon excited (TPE) luminescence of captured single living cells labeled with core-shell fluorescent semiconductor quantum dots (QDs). The QDs were obtained via colloidal synthesis in aqueous medium with an adequate physiological resulting pH. Sodium polyphosphate was used as the stabilizing agent. The results obtained show the potential presented by this system as well as by these II-VI fluorescent semiconductor quantum dots to perform spectroscopy in living trapped cells in any neighborhood and dynamically observe the cell chemical reactions in real time. 相似文献
992.
Szmidt-Jaworska A Jaworski K Kopcewicz J 《Journal of photochemistry and photobiology. B, Biology》2008,93(1):9-15
Cyclic GMP acts as a chemical switch in plant cells to modulate cellular reactions. However, its metabolism has not been extensively explored and is still poorly understood. Previous experiments suggest that an endogenous cGMP system could participate in the mechanism of phytochrome controlled photoperiodic flower induction in Pharbitis nil. In order to gain further information on the role of cGMP, we have begun to study the enzyme of cGMP synthesis. In this article, the presence of the enzyme with guanylyl cyclase (GC) activity in soluble protein fractions of P. nil is reported. A large portion of the enzymatic activity is present in the cotyledons, where enzyme activity amounted to 0.45 pmol cGMP/min/mg protein. The enzyme exhibited a K(m) 0.5mM for GTP. A plot of 1/v versus 1/[GTP] was linear and V(max) was 0.74 pmol cGMP/min/mg protein. It was shown that the anti-sGC antibody recognise a 40 kDa protein. Moreover, the NO-donor, sodium nitroprusside (SNP) and YC-1, as a NO-independent stimulator, enhanced enzyme activity. The NS 2028 (a potent GC inhibitor) treatments provoked a 3-fold reduction of the enzyme activity in comparison to the untreated fractions. Furthermore, the influence of light on GC activity was analysed. It was noted that cGMP level increased in cool white light, and darkness inhibited enzyme activity. Exposure to blue light acts to stimulate cGMP formation, whereas in red light a rapid decrease in GC activity was observed that returned to the high level when far-red light was applied after the red light treatment. The results presented in this work strongly argue that an enzyme with guanylyl cyclase activity is present in P. nil organs and its activity is controlled by light via the photoreceptors-dependent pathways. 相似文献
993.
Erika Scavetta Lorella Guadagnini Adriana Mignani Domenica Tonelli 《Electroanalysis》2008,20(20):2199-2204
An amperometric biosensor based on Pt electrodes modified with a thin film of a Ni, Al layered double hydroxide (LDH), submitted to a preliminary oxidative treatment in order to have the nickel centers at the oxidation state +4, and glucose oxidase (GOx) is presented. The oxidized LDH acts both as a system to support the enzyme and as a barrier to anions since it acquires an overall negative charge, as demonstrated by electrochemical impedance spectroscopy. Even if the biosensor response is due to the detection of H2O2 at anodic potentials, glucose can be accurately determined in the presence of ascorbic acid or other interferences, commonly present in real matrices in anionic form, since they can not reach the electrode surface. The effectiveness of the developed biosensor has been demonstrated by measuring glucose in samples of fruit juices containing ascorbic acid at high levels. 相似文献
994.
Marko Kullapere Margus Marandi Leonard Matisen Fakhradin Mirkhalaf Adriana E. Carvalho Gilberto Maia V?ino Sammelselg Kaido Tammeveski 《Journal of Solid State Electrochemistry》2012,16(2):569-578
The electrochemical properties of Au electrodes grafted with 4-nitrophenyl and 4-decylphenyl groups have been studied. The
electrografting of gold electrode surface with aryl groups was carried out by electroreduction of the corresponding diazonium
salts in acetonitrile. The nitrophenyl film growth on gold was examined by atomic force microscopy, electrochemical quartz
crystal microbalance and X-ray photoelectron spectroscopy. These measurements showed that a multilayer film of nitrophenyl
groups was formed. Cyclic voltammetry was used to study the blocking properties of aryl-modified gold electrodes towards the
Fe(CN)63−/4− redox system. The reduction of oxygen was strongly suppressed on these electrodes as evidenced by the rotating disc electrode
results. 相似文献
995.
Incorporation of nano-Al2O3 particles into a Ni–Co alloy by electrodeposition influences the corrosion properties, morphology, and structure of the layers. The resistance against corrosion of Ni–Co/Al2O3 composite films deposited on stainless steel was investigated in a 0.1-M NaCl solution by potentiodynamic polarization. The presence of nanoparticles improves the corrosion resistance of Ni–Co/nano-Al2O3 deposits when compared to pure Ni–Co alloy. Moreover, by increasing the pH of the electrodeposition bath and the content of Co in the alloy, the resistance against corrosion is furthermore improved. The morphology of the deposits before and after their corrosion was analyzed by scanning electron microscopy. The presence of the embedded alumina particles in the Ni–Co alloys was one of the key factors that limited further propagation of corrosion on the metallic surface. Preferential corrosion attack, in the form of a pitting corrosion, was located mainly at the grain boundaries. 相似文献
996.
Dr. Erhan Deniz Noufal Kandoth Dr. Aurore Fraix Dr. Venera Cardile Dr. Adriana C. E. Graziano Dr. Debora Lo Furno Dr. Ruxandra Gref Prof. Françisco M. Raymo Prof. Salvatore Sortino 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(49):15782-15787
A viable strategy to encapsulate a fluorophore/photochrome dyad and a nitric oxide photodonor within supramolecular assemblies of a cyclodextrin‐based polymer in water was developed. The two photoresponsive guests do not interact with each other within their supramolecular container and can be operated in parallel under optical control. Specifically, the dyad permits the reversible switching of fluorescence on a microsecond timescale for hundreds of cycles, and the photodonor enables the irreversible release of nitric oxide. Furthermore, these supramolecular assemblies cross the membrane of human melanoma cancer cells and transport their cargo in the cytosol. The fluorescence of one component allows the visualization of the labeled cells, and its switchable character could, in principle, be used to acquire super‐resolution images, while the release of nitric oxide from the other induces significant cell mortality. Thus, our design logic for the construction of biocompatible nanoparticles with dual functionality might evolve into the realization of valuable photoresponsive probes for imaging and therapeutic applications. 相似文献
997.
C Barea A Pabón S Galiano S Pérez-Silanes G Gonzalez C Deyssard A Monge E Deharo I Aldana 《Molecules (Basel, Switzerland)》2012,17(8):9451-9461
Malaria and leishmaniasis are two of the World's most important tropical parasitic diseases. Thirteen new 2-cyano-3-(4-phenylpiperazine-1-carboxamido) quinoxaline 1,4-dioxide derivatives (CPCQs) were synthesized and evaluated for their in vitro antimalarial and antileishmanial activity against erythrocytic forms of Plasmodium falciparum and axenic forms of Leishmania infantum. Their toxicity against VERO cells (normal monkey kidney cells) was also assessed. None of the tested compounds was efficient against Plasmodium, but two of them showed good activity against Leishmania. Toxicity on VERO was correlated with leishmanicidal properties. 相似文献
998.
Among the many aspects of laser ablation, development of conical structures induced by excimer laser radiation on polyimide surfaces has been thoroughly investigated. Because the mechanisms that produce these surface textures are not fully understood, two theories, photochemical bond breaking and thermal reaction, have been introduced. Here we present the first study of ultraviolet laser ablation behavior of thin films made from fluorinated poly(naphthyl-imide)s containing oxadiazole rings and the investigation of the mechanism of cone-like structure formation at two laser fluences, 57 and 240 mJ/cm(2). The morphology of thin films before and after laser ablation was studied by using various spectroscopy techniques such as Fourier transform infrared spectroscopy, time-resolved emission and X-ray photoelectron spectroscopy, atomic force microscopy, and contact angle measurements. All of the data suggest impurities shielded at low fluence radiation (57 mJ/cm(2)) and a radiation hardening process at high value fluence (240 mJ/cm(2)), which are proposed as the main mechanisms for laser ablation of our polyimide films, and we bring evidence to support them. 相似文献
999.
The reactions of the ligands 2,6-(Me2NCH2)2C5H3N (N’NN’) (1) and 2,6-(PhSeCH2)2C5H3N (SeNSe) (4) with different coinage metal starting materials gave 1:1, 2:1 or 1:2 metal-to-ligand species, i.e. [Ag(N’NN’){O(O)CCF3}] (2), [{Ag(PPh3)}2(N’NN’)](OTf)2 (3), [Au(SeNSe)Cl]Cl2 (5), [Ag(PPh3)(SeNSe)](OTf) (6), [Cu(MeCN)(SeNSe)](PF6) (7) or [Cu(SeNSe)2](PF6) (8). The new compounds were investigated by IR, multinuclear NMR spectroscopies as well as mass spectrometry. In most cases, the ligands 1 and 4 act as pincer ligands. An attempt to grow single crystals of 2 gave an unexpected result. The crystal investigated by X-ray diffraction proved to be a polynuclear species, [Ag4(N’NN’){O(O)CCF3}4(EtOH)]n (2a), which contains an unusual, bimetallic triconnective coordination pattern of the N’NN’ ligand. Two tetranuclear [Ag4(N’NN’){O(O)CCF3}4(EtOH)] units form centrosymmetric dimers further associated into a polymer which contains four different coordination environments around silver atoms. The complex 3, in which the ligand also exhibits a bimetallic triconnective pattern, shows an intense, long-lived luminescence in the solid state with emission energies in the green region of the visible spectrum. 相似文献
1000.
Aurelia Visa Maria Mracec Bianca Maranescu Valentin Maranescu Gheorghe Ilia Adriana Popa Mircea Mracec 《Chemistry Central journal》2012,6(1):1-8