Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 24
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
J Hazard Mater ; 383: 120950, 2020 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-31541960

RESUMO

The adsorption of Cu(II) ions by biochar fibres prior and after modification with 2-thiouracil on real and artificial samples has been studied by batch-type adsorption experiments, FTIR and XPS spectroscopy and competition reactions using U(VI) ions as competitor cations. The experimental data of the artificial samples clearly show that the modified material presents extraordinary higher affinity for Cu(II) ions even in the acidic pH range, the spectroscopic data indicate the formation of inner-sphere complexes and the competition reactions significantly higher selectivity of the 2-thiouracil modified biochar fibres for Cu(II). The 2-thiouracil-modified biochar fibres have been successfully applied to acid mine drainage (AMD) samples regarding the selective separation of Cu(II) ions from "real" samples. Regarding the desorption of copper from the biochar surface, although 100% copper recovery was achieved by eluting the metal ion using 1 M HNO3, the deterioration of the modified biochar fibers due to extensive 2-thiouracil release from the biochar surface limits the applicability of the present adsorbent in routine and large-scale applications.

2.
J Environ Manage ; 252: 109677, 2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-31629175

RESUMO

This work investigates the fabrication of magnetic biochar (pncm) and Fe3O4-loaded oxidized biochar (pncom) obtained from pine needles for uranium removal. Adsorbent properties were characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) techniques. Using batch-type experiments the effect of the uranium concentration, solution pH, contact time, temperature and ionic strength on the uranium adsorption was investigated. The results showed better adsorptive properties for pncom, particularly in the acidic pH range. The experimental adsorption data were found to be well fitted with the Langmuir isotherm and the pseudo-second order kinetic model. For pncom, the maximum adsorption capacity obtained applying the Langmuir isotherm model was found to amount 2.6 mol/kg at pH 6 and 25 °C. Spectroscopic data indicated that the U(VI) adsorption was associated with the formation of inner-sphere complexes. Regeneration and reusability studies were performed with 0.1 M Na2CO3. After four cycles, the % relative adsorption and the desorption for pncom decreased from 99.5% to 87.2% and 99.6%-62.6%, respectively. The present results show that magnetization of oxidized pine needle biochar improves significantly the adsorption characteristics regarding the uranium removal from aqueous solutions.


Assuntos
Urânio , Poluentes Químicos da Água , Adsorção , Carvão Vegetal , Concentração de Íons de Hidrogênio , Cinética , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica
3.
Chemphyschem ; 20(22): 3010-3023, 2019 11 19.
Artigo em Inglês | MEDLINE | ID: mdl-31538400

RESUMO

We investigated the formation of Pt nanocubes (NCs) and their electrocatalytic oxygen reduction reaction (ORR) properties and structural stability using two different capping agents, namely, polyvinylpyrrolidone (PVP) and oleylamine (OAm). The mono-dispersity of the obtained Pt NCs and their interactions with PVP and OAm were analyzed by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Fourier-transformed infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The TEM data show a high mono-dispersity (82 %) and a large mean particle size (9-10 nm) for the Pt NCs obtained by the oleylamine-assisted method compared to those prepared via the PVP-assisted procedure (68 %, 6-7 nm). FTIR, XPS, and TGA data show that PVP and OAm still remain at the Pt surface, despite washing. Interestingly, the OAm-capped Pt NCs show significantly higher electrochemically active surface area (ECSA) and ORR activity than the PVP-capped ones. An accelerated stress protocol, however, reveals that the OAm-capped NCs possess a poor structural stability during electrochemical cycling. The loss of a defined surface arrangement in the NCs is connected with a transformation into a near-spherical particle shape. In contrast, the PVP-capped NCs mainly retain their particle shape due to their strong capping behavior. In addition, we have developed a degradation model for NCs as a function of electrochemical parameters such as upper potential and cycle number. Altogether, we provide fundamental insights into the electronic interactions between capping agent and Pt NCs and the role of the adsorption strength of the capping agent in improving the electrochemical ORR performance as well as the structural stability of shape-controlled nanoparticles.

4.
Inorg Chem ; 58(10): 7010-7025, 2019 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-31062962

RESUMO

A total of 35 intermetallic aluminum compounds have been synthesized from the elements via arc melting and characterized by powder X-ray diffraction. A total of 15 of them have been previously reported; however, detailed property investigations were missing. Compounds of the RETMAl2 (rare earth metal RE = Sc, Y, La-Nd, Sm, Gd-Tm, Lu) series with transition metal TM = Ni, Pd, and Pt crystallize isostructurally in the orthorhombic MgCuAl2 type structure ( Cmcm, oC16, fc2). Single-crystal X-ray diffraction investigations were conducted on YNiAl2, LaNiAl2, YPdAl2, ScPtAl2, and YPtAl2. The TM and Al atoms form a [TMAl2]δ- polyanion, the RE atoms reside in cavities within the framework. While the Sc, Y, La, and Lu compounds exhibit Pauli-paramagnetic behavior, consistent with all atoms being closed shell, the other RETMAl2 compounds show paramagnetism along with magnetic ordering at low temperatures, in line with an open-shell trivalent oxidation state for the RE atoms. Solid-state 27Al NMR investigations were carried out on the Pauli-paramagnetic samples, all showing only a single central transition, in line with one crystallographic site for the respective atoms. The observed quadrupolar coupling constants and electric-field-gradient asymmetry parameters were found to be in good agreement with the density-functional-theory-calculated values. Isotropic resonance shifts are dominated by the Fermi-contact interactions with s-conduction electron densities at the Fermi edge (Knight shifts). The bonding characteristics mirror the electronic density of states and crystal chemistry of the family of intermetallic compounds under consideration. Both the Knight shifts and quadrupolar coupling constants can be predicted based on element-specific increments.

5.
Chemistry ; 25(27): 6763-6772, 2019 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-30829419

RESUMO

A new preparation route is developed for the synthesis of needle-like crystals of [Au(S2 CNH2 )2 ]SCN, which avoids disproportionation of the AuI salt used as a starting material. In the crystal structure, the two crystallographically independent AuIII centers are in a square-planar environment of two S2 CNH2 ligands. The Hirshfeld surface analysis reveals the presence of noncovalent intermolecular S⋅⋅⋅S interactions, which are essential for the spatial arrangement of the molecules. Density functional theory (DFT) calculations including dispersion and damping corrections result in a unit cell volume very close to the value determined experimentally. Thermal decomposition in an inert atmosphere generates black needles with lengths of up to 500 µm. X-ray powder diffraction and pair distribution function analyses demonstrate that the needles are composed of nanosized crystals with a volume-weighted average domain size of 20(1) nm. According to results of X-ray photoemission experiments, the black needles are covered by a nitrogen-rich carbon nitride with composition near (CN)2 N. 13 C solid-state NMR investigations indicate that two different carbon species are present, with signals corresponding well to heptazine units as in melon and triazine units as in poly(triazin imide) type compounds. Scanning transmission electron microscopy tomography evidences that the needles are composed of slightly elongated nanoparticles.

6.
Appl Spectrosc ; 68(9): 1030-8, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25226257

RESUMO

In this paper the concept of a compact high-resolution spectrometer based on the combination of dispersive and interferometric elements is presented. Dispersive elements are used to spectrally resolve the light in one direction with coarse resolution (Δλ < 0.5 nm), while perpendicular to that direction an etalon provides high spectral resolution (Δλ < 50 pm). This concept for two-dimensional spectroscopy has been implemented for the wavelength range λ = 350-650 nm. Appropriate algorithms for reconstructing spectra from the two-dimensional raw data and for wavelength calibration were established in an analysis software. Potential applications for this new spectrometer are Raman and laser-induced breakdown spectroscopy (LIBS). Resolutions down to 28 pm (routinely 54 pm) could be realized for these applications.

7.
Anal Chem ; 86(1): 713-20, 2014 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-24328212

RESUMO

Scanning electrochemical microscopy with soft microelectrode array probes has recently been used to enable reactivity imaging of extended areas and to compensate sample corrugation perpendicular to the scanning direction. Here, the use of a new type of microelectrode arrays is described in which each individual microelectrode can independently compensate corrugations of the sample surface. It consists of conventional Pt microelectrodes enclosed in an insulating glass sheath. The microelectrodes are individually fixed to a new holder system by magnetic forces. The concept was tested using a large 3D sample with heights up to 12 µm specially prepared by inkjet printing. The microelectrodes follow the topography in a constant working distance independently from each other while exerting low pressure on the surface.


Assuntos
Microscopia Eletroquímica de Varredura/instrumentação , Microscopia Eletroquímica de Varredura/métodos , Microeletrodos
8.
PLoS One ; 8(4): e60869, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23593335

RESUMO

In humans, the L-cysteine desulfurase NFS1 plays a crucial role in the mitochondrial iron-sulfur cluster biosynthesis and in the thiomodification of mitochondrial and cytosolic tRNAs. We have previously demonstrated that purified NFS1 is able to transfer sulfur to the C-terminal domain of MOCS3, a cytosolic protein involved in molybdenum cofactor biosynthesis and tRNA thiolation. However, no direct evidence existed so far for the interaction of NFS1 and MOCS3 in the cytosol of human cells. Here, we present direct data to show the interaction of NFS1 and MOCS3 in the cytosol of human cells using Förster resonance energy transfer and a split-EGFP system. The colocalization of NFS1 and MOCS3 in the cytosol was confirmed by immunodetection of fractionated cells and localization studies using confocal fluorescence microscopy. Purified NFS1 was used to reconstitute the lacking molybdoenzyme activity of the Neurospora crassa nit-1 mutant, giving additional evidence that NFS1 is the sulfur donor for Moco biosynthesis in eukaryotes in general.


Assuntos
Liases de Carbono-Enxofre/metabolismo , Coenzimas/biossíntese , Cisteína/metabolismo , Citosol/metabolismo , Metaloproteínas/biossíntese , Enxofre/metabolismo , Transferência Ressonante de Energia de Fluorescência , Proteínas de Fluorescência Verde/metabolismo , Células HeLa , Humanos , Microscopia de Fluorescência , Proteínas Mutantes/metabolismo , Neurospora/enzimologia , Nitrato Redutase/metabolismo , Nucleotidiltransferases/metabolismo , Mapeamento de Interação de Proteínas , Transporte Proteico , Pteridinas , Proteínas Recombinantes de Fusão/metabolismo , Frações Subcelulares/metabolismo , Sulfurtransferases/metabolismo , Ressonância de Plasmônio de Superfície
9.
Dalton Trans ; 41(34): 10219-27, 2012 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-22777213

RESUMO

A series of new monocationic iridium(III) complexes [Ir(C^N)(2)(N^N)]PF(6) with "large-surface"α,α'-diimin ligands N^N (dap = 1,12-diazaperylene, dmedap = 2,11-dimethyl-1,12-diazaperylene, dipdap = 2,11-diisopropyl-1,12-diazaperylene) and different cyclometalating ligands C^N (piq = 1-phenylisoquinoline, bzq = benzo[h]quinoline, ppz = 1-phenylpyrazole, thpy = 2-(2-thienyl)pyridine, ppy = 2-phenylpyridine, meppy = 2-(4-methylphenyl)pyridine, dfppy = 2-(2,4-difluorophenyl)pyridine) were synthesized. The solid structures of the complexes [Ir(piq)(2)(dap)]PF(6), [Ir(bzq)(2)(dap)]PF(6), [Ir(ppy)(2)(dipdap)]PF(6), [Ir(piq)(2)(dmedap)]PF(6), [Ir(ppy)(2)(dap)]PF(6) and [Ir(ppz)(2)(dap)]PF(6) are reported. In [Ir(piq)(2)(dap)]PF(6), the dap ligand and one of the piq ligands of each cationic complex are involved in π-π stacking interactions forming supramolecular channels running along the crystallographic c axis. In the crystalline [Ir(bzq)(2)(dap)]PF(6)π-π stacking interactions between the metal complexes lead to the formation of a 2D layer structure. In addition, CH-π interactions were found in all compounds, which are what stabilizes the solid structure. In particular, a significant number of them were found in [Ir(piq)(2)(dap)]PF(6) and [Ir(bzq)(2)(dap)]PF(6). The crystal structures of [Ir(ppy)(2)(dipdap)]PF(6) and [Ir(ppy)(2)(dmedap)]PF(6) are also presented, being the first examples of bis-cyclometalated iridium(iii) complexes with phenanthroline-type α,α'-diimin ligands bearing bulky alkyl groups in the neighbourhood of the N-donor atoms. These ligands implicate a distorted octahedral coordination geometry that in turn destabilized the Ir-N(N^N) bonds. The new iridium(iii) complexes are not luminescent. All compounds show an electrochemically irreversible anodic peak between 1.15 and 1.58 V, which is influenced by the different cyclometalated ligands. All of the new complexes show two reversible successive one-electron "large-surface" ligand-centred reductions around -0.70 V and -1.30 V. Electrospray ionisation mass spectrometry (ESI-MS) and collision induced decomposition (CID) measurements were used to investigate the stability of the new complexes. Thereby, the stability agreed well with the order of the Ir-N(N^N) bond lengths.

10.
J Colloid Interface Sci ; 377(1): 251-61, 2012 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-22520209

RESUMO

The well-known cationic surfactant hexadecyltrimethylammonium bromide (CTAB) was used as a model carrier to study drug-carrier interactions with fluorescence probes (5-hexadecanoylaminofluorescein (HAF) and 2,10-bis-(3-aminopropyloxy)dibenzo[a,j]perylene-8,16-dione (NIR 628) by applying ensemble as well as single molecule fluorescence techniques. The impact of the probes on the micelle parameters (critical micelle concentration, average aggregation number, hydrodynamic radius) was investigated under physiological conditions. In the presence of additional electrolytes, such as buffer, the critical micelle concentration decreased by a factor of about 10. In contrast, no influence of the probes on the critical micelle concentration and on average aggregation number was observed. The results show that HAF does not affect the characteristics of CTAB micelles. Analyzing fluorescence correlation spectroscopy data and time-resolved anisotropy decays in terms of the "two-step" in combination with the "wobbling-in-cone" model, it was proven that HAF and NIR 628 are differently associated with the micelles. Based on ensemble and single molecule fluorescence experiments, intra- and intermicellar energy transfer process between the two dyes were probed and characterized.


Assuntos
Compostos de Cetrimônio/química , Portadores de Fármacos/química , Corantes Fluorescentes/química , Fosfatos/química , Tensoativos/química , Tampões (Química) , Cetrimônio , Modelos Moleculares , Estrutura Molecular , Espectrometria de Fluorescência
11.
J Biol Chem ; 287(21): 17297-307, 2012 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-22453920

RESUMO

We studied two pathways that involve the transfer of persulfide sulfur in humans, molybdenum cofactor biosynthesis and tRNA thiolation. Investigations using human cells showed that the two-domain protein MOCS3 is shared between both pathways. MOCS3 has an N-terminal adenylation domain and a C-terminal rhodanese-like domain. We showed that MOCS3 activates both MOCS2A and URM1 by adenylation and a subsequent sulfur transfer step for the formation of the thiocarboxylate group at the C terminus of each protein. MOCS2A and URM1 are ß-grasp fold proteins that contain a highly conserved C-terminal double glycine motif. The role of the terminal glycine of MOCS2A and URM1 was examined for the interaction and the cellular localization with MOCS3. Deletion of the C-terminal glycine of either MOCS2A or URM1 resulted in a loss of interaction with MOCS3. Enhanced cyan fluorescent protein and enhanced yellow fluorescent protein fusions of the proteins were constructed, and the fluorescence resonance energy transfer efficiency was determined by the decrease in the donor lifetime. The cellular localization results showed that extension of the C terminus with an additional glycine of MOCS2A and URM1 altered the localization of MOCS3 from the cytosol to the nucleus.


Assuntos
Núcleo Celular/metabolismo , Coenzimas/biossíntese , Citosol/metabolismo , Metaloproteínas/biossíntese , Nucleotidiltransferases/metabolismo , RNA de Transferência/metabolismo , Sulfurtransferases/metabolismo , Transporte Ativo do Núcleo Celular/fisiologia , Motivos de Aminoácidos , Animais , Núcleo Celular/genética , Coenzimas/genética , Células HEK293 , Células HeLa , Humanos , Metaloproteínas/genética , Nucleotidiltransferases/genética , Dobramento de Proteína , Pteridinas , RNA de Transferência/genética , Spodoptera , Sulfurtransferases/genética , Ubiquitinas/genética , Ubiquitinas/metabolismo
12.
J Chem Phys ; 136(9): 094905, 2012 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-22401471

RESUMO

The intrinsic non-radiative decay (internal conversion) from the triplet excited state in phosphorescent dyes can be described by a multi-phonon emission process. Since non-radiative decay of triplet excitons can be a significant process in organic light-emitting diodes, a detailed understanding of this decay mechanism is important if the overall device efficiency is to be controlled. We compare a deuterated Pt(II)-containing phenylene ethynylene with its non-deuterated counterpart in order to investigate which phonon modes control to the non-radiative decay path. We observe that deuteration does not decrease the non-radiative decay rate. A Franck-Condon analysis of the phosphorescence spectra shows that the electronic excitation is coupled strongly to the breathing mode of the phenyl ring and the C≡C carbon stretching modes, while high-energy C-H or C-D stretching modes play an insignificant role. We, therefore, associate the internal conversion process with the carbon-carbon stretching vibrations.

13.
J Biol Chem ; 286(34): 30200-10, 2011 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-21737451

RESUMO

Active transport of NaCl across thick ascending limb (TAL) epithelium is accomplished by Na(+),K(+),2Cl(-) cotransporter (NKCC2). The activity of NKCC2 is determined by vasopressin (AVP) or intracellular chloride concentration and includes its amino-terminal phosphorylation. Co-expressed Tamm-Horsfall protein (THP) has been proposed to interact with NKCC2. We hypothesized that THP modulates NKCC2 activity in TAL. THP-deficient mice (THP(-/-)) showed an increased abundance of intracellular NKCC2 located in subapical vesicles (+47% compared with wild type (WT) mice), whereas base-line phosphorylation of NKCC2 was significantly decreased (-49% compared with WT mice), suggesting reduced activity of the transporter in the absence of THP. Cultured TAL cells with low endogenous THP levels and low base-line phosphorylation of NKCC2 displayed sharp increases in NKCC2 phosphorylation (+38%) along with a significant change of intracellular chloride concentration upon transfection with THP. In NKCC2-expressing frog oocytes, co-injection with THP cRNA significantly enhanced the activation of NKCC2 under low chloride hypotonic stress (+112% versus +235%). Short term (30 min) stimulation of the vasopressin V2 receptor pathway by V2 receptor agonist (deamino-cis-D-Arg vasopressin) resulted in enhanced NKCC2 phosphorylation in WT mice and cultured TAL cells transfected with THP, whereas in the absence of THP, NKCC2 phosphorylation upon deamino-cis-D-Arg vasopressin was blunted in both systems. Attenuated effects of furosemide along with functional and structural adaptation of the distal convoluted tubule in THP(-/-) mice supported the notion that NaCl reabsorption was impaired in TAL lacking THP. In summary, these results are compatible with a permissive role for THP in the modulation of NKCC2-dependent TAL salt reabsorptive function.


Assuntos
Cloretos/metabolismo , Túbulos Renais Distais/metabolismo , Simportadores de Cloreto de Sódio-Potássio/metabolismo , Uromodulina/metabolismo , Animais , Antidiuréticos/farmacologia , Linhagem Celular Transformada , Desamino Arginina Vasopressina/farmacologia , Camundongos , Camundongos Knockout , Pressão Osmótica , Fosforilação/efeitos dos fármacos , Fosforilação/fisiologia , Coelhos , Receptores de Vasopressinas/genética , Receptores de Vasopressinas/metabolismo , Simportadores de Cloreto de Sódio-Potássio/genética , Membro 1 da Família 12 de Carreador de Soluto , Uromodulina/genética , Xenopus laevis
14.
Am J Physiol Cell Physiol ; 300(6): C1323-36, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21346157

RESUMO

The intracellular ion homeostasis in cockroach salivary acinar cells during salivation is not satisfactorily understood. This is mainly due to technical problems regarding strong tissue autofluorescence and ineffective ion concentration quantification. For minimizing these problems, we describe the successful application of two-photon (2P) microscopy partly in combination with fluorescence lifetime imaging microscopy (FLIM) to record intracellular Na(+) and Cl(-) concentrations ([Na(+)](i), [Cl(-)](i)) in cockroach salivary acinar cells. Quantitative 2P-FLIM Cl(-) measurements with the dye N-(ethoxycarbonylmethyl)-6-methoxy-quinolinium bromide indicate that the resting [Cl(-)](i) is 1.6 times above the Cl(-) electrochemical equilibrium but is not influenced by pharmacological inhibition of the Na(+)-K(+)-2Cl(-) cotransporter (NKCC) and anion exchanger using bumetanide and 4,4'-diisothiocyanatodihydrostilbene-2,2'-disulfonic acid disodium salt. In contrast, rapid Cl(-) reuptake after extracellular Cl(-) removal is almost totally NKCC mediated both in the absence and presence of dopamine. However, in physiological saline [Cl(-)](i) does not change during dopamine stimulation although dopamine stimulates fluid secretion in these glands. On the other hand, dopamine causes a decrease in the sodium-binding benzofuran isophthalate tetra-ammonium salt (SBFI) fluorescence and an increase in the Sodium Green fluorescence after 2P excitation. This opposite behavior of both dyes suggests a dopamine-induced [Na(+)](i) rise in the acinar cells, which is supported by the determined 2P-action cross sections of SBFI. The [Na(+)](i) rise is Cl(-) dependent and inhibited by bumetanide. The Ca(2+)-ionophore ionomycin also causes a bumetanide-sensitive [Na(+)](i) rise. We propose that a Ca(2+)-mediated NKCC activity in acinar peripheral cells attributable to dopamine stimulation serves for basolateral Na(+) uptake during saliva secretion and that the concomitantly transported Cl(-) is recycled back to the bath.


Assuntos
Cloretos/metabolismo , Baratas/citologia , Baratas/metabolismo , Microscopia de Fluorescência/métodos , Sódio/metabolismo , Animais , Bumetanida/metabolismo , Dopamina/metabolismo , Fluorescência , Corantes Fluorescentes/metabolismo , Compostos de Quinolínio/metabolismo , Glândulas Salivares/citologia , Inibidores de Simportadores de Cloreto de Sódio e Potássio/metabolismo , Simportadores de Cloreto de Sódio-Potássio/metabolismo
15.
Biochemistry ; 50(12): 2048-60, 2011 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-21332223

RESUMO

In response to stress small organic compounds termed osmolytes are ubiquitously accumulated in all cell types to regulate the intracellular solvent quality and to counteract the deleterious effect on the stability and function of cellular proteins. Given the evidence that destabilization of the native state of a protein either by mutation or by environmental changes triggers the aggregation in the neurodegenerative pathologies, the modulation of the intracellular solute composition with osmolytes is an attractive strategy to stabilize an aggregating protein. Here we report the effect of three natural osmolytes on the in vivo and in vitro aggregation landscape of huntingtin exon 1 implicated in the Huntington's disease. Trimethylamine N-oxide (TMAO) and proline redirect amyloid fibrillogenesis of the pathological huntingtin exon 1 to nonamyloidogenic amorphous assemblies via two dissimilar molecular mechanisms. TMAO causes a rapid formation of bulky amorphous aggregates with minimally exposed surface area, whereas proline solubilizes the monomer and suppresses the accumulation of early transient aggregates. Conversely, glycine-betaine enhances fibrillization in a fashion reminiscent of the genesis of functional amyloids. Strikingly, none of the natural osmolytes can completely abrogate the aggregate formation; however, they redirect the amyloidogenesis into alternative, nontoxic aggregate species. Our study reveals new insights into the complex interactions of osmoprotectants with polyQ aggregates.


Assuntos
Produtos Biológicos/farmacologia , Éxons , Proteínas Mutantes/química , Mutação , Proteínas do Tecido Nervoso/química , Osmose/efeitos dos fármacos , Multimerização Proteica/efeitos dos fármacos , Animais , Betaína/farmacologia , Metilaminas/farmacologia , Proteínas Mutantes/genética , Proteínas Mutantes/metabolismo , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Peptídeos/química , Peptídeos/metabolismo , Prolina/farmacologia , Estrutura Quaternária de Proteína , Solubilidade
16.
Chem Commun (Camb) ; 46(12): 2034-6, 2010 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-20221483

RESUMO

The [6.6](9,10)anthracenophane 1 (Scheme 1) is a selective fluoroionophore for the detection of PdCl(2) with a large fluorescence enhancement factor (I/I(0) > 250).

17.
Chemistry ; 16(6): 1819-25, 2010 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-20024987

RESUMO

Fluoroionophores of fluorophore-spacer-receptor format were prepared for detection of PdCl(2) by fluorescence enhancement. The fluorescent probes 1-13 consist of a fluorophore group, an alkyl spacer and a dithiomaleonitrile PdCl(2) receptor. First, varying the length of the alkylene spacer (compounds 1-3) revealed a dominant through-space pathway for oxidative photoinduced electron transfer (PET) in CH(2)-bridged dithiomaleonitrile fluoroionophores. Second, fluorescent probes 4-9 containing two anthracene or pyrene fragments connected through CH(2) bridges to the dithiomaleonitrile unit were synthesized. Modulation of the oxidation potential (E(Ox)) through electron-withdrawing or -donating groups on the anthracene moiety regulates the thermodynamic driving force for oxidative PET (DeltaG(PET)) in bis(anthrylmethylthio)maleonitriles and therefore the fluorescence quantum yields (Phi(f)), too. The new concept was confirmed and transferred to pyrenyl ligands, and fluorescence enhancements (FE) greater than 3.2 in the presence of PdCl(2) were achieved by 7 and 8 (FE=5.4 and 5.2). Finally, for comparison, monofluorophore ligands 10-13 were synthesized.


Assuntos
Eletroquímica/métodos , Transporte de Elétrons , Corantes Fluorescentes/química , Oxirredução/efeitos dos fármacos , Paládio/química , Elétrons/efeitos adversos , Estrutura Molecular , Fotoquímica/métodos , Espectrometria de Fluorescência , Espectrofotometria Ultravioleta , Eletricidade Estática/efeitos adversos , Temperatura , Termodinâmica
18.
Org Biomol Chem ; 7(24): 5259-70, 2009 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-20024123

RESUMO

A series of new ligands suitable for the formation of luminescent lanthanide complexes in water is described. The chelates are designed for analyte labeling and play the role of fluorescent donor in homogeneous time-resolved fluorescence assays using LEDs as a light source for excitation at 370 nm. Ligands are constructed from a coumarin nucleus, for lanthanide sensitization, and different aminomethylenecarboxy moieties are introduced in positions 7 and 5, 6, or 8 of the sensitizer. A reactive spacer arm under biocompatible conditions (maleimide, azide) is introduced at position 3 for ultimate bioconjugation purposes. The synthesis and characterization of the ligands are described, together with the preparation of their corresponding europium complexes. Photophysical properties of the complexes are investigated in water by means of UV-vis and luminescence spectroscopy.


Assuntos
Cumarínicos/síntese química , Európio , Medições Luminescentes/métodos , Compostos Organometálicos/síntese química , Reagentes para Ligações Cruzadas , Ligantes , Soluções , Espectrofotometria Ultravioleta , Água
19.
J Colloid Interface Sci ; 338(1): 312-5, 2009 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-19631944

RESUMO

In our study we determined the diffusion coefficient of Tween 20 micelles at different surfactant concentrations (10(-4)-10(-2) M) via fluorescence correlation spectroscopy. The hydrophobic fluorescent dye 9,10-bis(phenylethynyl)anthracene, located in the micellar phase, was used as marker for the diffusion of Tween 20 micelles. The hydrodynamic radius of the micelles, R(h), was estimated from the diffusion coefficient and compared with literature values from previous studies.


Assuntos
Alquinos/química , Antracenos/química , Corantes Fluorescentes/química , Micelas , Tensoativos/química , Difusão , Estrutura Molecular , Polissorbatos/química , Rodaminas/química
20.
Photochem Photobiol Sci ; 8(3): 319-27, 2009 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-19255672

RESUMO

Although chloride plays an important role in many cellular processes, there is a lack of data about intracellular chloride concentrations [Cl(-)](i), particularly due to technical problems. To overcome that, in this study fluorescence lifetime imaging microscopy in the time-domain by using time-correlated single-photon counting was combined with two-photon excitation (2P-FLIM). This 2P-FLIM setup has been successfully used with the Cl(-)-sensitive fluorescent dye N-(ethoxycarbonylmethyl)-6-methoxy-quinolinium bromide (MQAE) in order to measure [Cl(-)](i) in cockroach salivary glands, a well-established model system for studying epithelial ion transport processes. MQAE was well suitable for two-photon excitation, when loaded into cells, and displayed a sufficient dynamic range of its fluorescence decay time changes in response to variation of [Cl(-)](i) according to the Stern-Volmer relationship. On this basis a uniform [Cl(-)](i) in the range of 42-80 mM with a mean value of 59 mM +/- 1 mM was found in resting cockroach salivary ducts, indicating active Cl(-) accumulation. However, exposure to Cl(-)-free saline caused only a moderate [Cl(-)](i) drop to 48 mM +/- 4 mM, suggesting a relatively low basolateral Cl(-) permeability in ducts, at least under resting conditions. Additionally, bath application of the biogenic amine dopamine, known to stimulate the saliva modification in the ducts, caused no significant [Cl(-)](i) changes. These results suggest a more complex scenario of [Cl(-)](i) homeostasis in cockroach salivary ducts. In conclusion, 2P-FLIM seems to be a suitable technique for quantitative [Cl(-)](i) measurements in many biological systems.


Assuntos
Cloretos/análise , Microscopia de Fluorescência por Excitação Multifotônica/métodos , Glândulas Salivares/química , Animais , Baratas/química , Baratas/efeitos da radiação , Corantes Fluorescentes/química , Fótons , Compostos de Quinolínio/química , Glândulas Salivares/efeitos da radiação
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA