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Talanta ; 222: 121413, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33167193


Only a limited and scattered knowledge is currently available on the conditions leading to the occurrence of sampling alteration at low ionic strength (<10-3 mol L-1) with DGT (diffusive gradients in thin films technique). In this study, the role of the pH and the charge of the analyte were comprehensively evaluated with DGT equipped with APA (polyacrylamide with agarose-derivative crosslinker) diffusive gels and ZrO or Chelex binding phases. The sampling of four cations (CdII, CuII, NiII and PbII) and two anions (AsV and CrVI) was compared for pH 4, 6 and 8 at common (10-2 mol L-1) and low (10-4 mol L-1) ionic strengths. Results showed that the sampling was modified at low ionic strength only in the most acidic condition (pH 4) for both anions and cations with an opposite incidence: cations' sampling was halved whereas anions' sampling was increased. Furthermore, cations sampling alteration was similarly reproduced using diffusion cell experiments, which requires only the APA gel, indicating that the binding layer does not participate in the low ionic strength effect. The intensity of DGT sampling modification was consistent with a prediction based on Donnan partitioning of analytes at gel/solution interface for several valences (from -I to + III). All these results strongly suggest that the APA diffusive gels carry positive charges that create a Donnan effect at low ionic strength. Since no ionic strength effect could be evidenced at pH 6 and 8, it can be reasonably assumed that this effect occurs only marginally for DGT deployments in most natural waters.

Talanta ; 199: 590-595, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-30952302


This study evaluates binding discs based on 3-mercaptopropyl-functionalized silica gel for the selective sampling of selenite (SeIV) using Diffusive Gradients in Thin films sampler (DGT). SeIV accumulation was quantitative and selective over SeVI and followed the theoretical linear accumulation with the exposure time up to 0.7 µg. The sampling was not affected by ionic strength variations down to 10-2 mol L-1 (as NaNO3) but SeIV accumulation was found to decrease significantly for pH greater than 5 and was nearly zero at pH 9. Both the limited accumulation range and the pH dependence were unexpected because they have not been reported in the literature related to the SeIV trapping by thiol-based solid phases. Our experiments showed that after SeIV was bound to thiol functional groups, a further pH-dependent reaction occurred with free thiols, resulting in the reduction of SeIV into elemental selenium (Se0) followed by its release and back-diffusion through the DGT sampler. Unfortunately, such a reversible accumulation is incompatible with the implementation of the mercapto-functionalized silica binding phase in DGT devices for SeIV selective sampling.

Adv Exp Med Biol ; 994: 169-179, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28560674


Circulating tumor cells (CTCs) hold promise as biomarkers to aid in patient treatment stratification and disease monitoring. Because the number of cells is a critical parameter for exploiting CTCs for predictive biomarker's detection, we developed a FISH (fluorescent in situ hybridization) method for CTCs enriched on filters (filter-adapted FISH [FA-FISH]) that was optimized for high cell recovery. To increase the feasibility and reliability of the analyses, we combined fluorescent staining and FA-FISH and developed a semi-automated microscopy method for optimal FISH signal identification in filtration-enriched CTCs . Here we present these methods and their use for the detection and characterization of ALK-, ROS1-, RET-rearrangement in CTCs from non-small-cell lung cancer and ERG-rearrangements in CTCs from prostate cancer patients.

Carcinoma Pulmonar de Células não Pequenas , Rearranjo Gênico , Neoplasias Pulmonares , Células Neoplásicas Circulantes/metabolismo , Neoplasias da Próstata , Proteínas Tirosina Quinases , Proteínas Proto-Oncogênicas c-ret , Proteínas Proto-Oncogênicas , Receptores Proteína Tirosina Quinases , Quinase do Linfoma Anaplásico , Carcinoma Pulmonar de Células não Pequenas/sangue , Carcinoma Pulmonar de Células não Pequenas/genética , Feminino , Humanos , Hibridização in Situ Fluorescente/instrumentação , Hibridização in Situ Fluorescente/métodos , Neoplasias Pulmonares/sangue , Neoplasias Pulmonares/genética , Masculino , Neoplasias da Próstata/sangue , Neoplasias da Próstata/genética , Proteínas Tirosina Quinases/genética , Proteínas Tirosina Quinases/metabolismo , Proteínas Proto-Oncogênicas/genética , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas c-ret/genética , Proteínas Proto-Oncogênicas c-ret/metabolismo , Receptores Proteína Tirosina Quinases/genética , Receptores Proteína Tirosina Quinases/metabolismo , Regulador Transcricional ERG/genética , Regulador Transcricional ERG/metabolismo
Nature ; 522(7555): 202-6, 2015 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-26062512


The relative motion of lithospheric plates and underlying mantle produces localized deformation near the lithosphere-asthenosphere boundary. The transition from rheologically stronger lithosphere to weaker asthenosphere may result from a small amount of melt or water in the asthenosphere, reducing viscosity. Either possibility may explain the seismic and electrical anomalies that extend to a depth of about 200 kilometres. However, the effect of melt on the physical properties of deformed materials at upper-mantle conditions remains poorly constrained. Here we present electrical anisotropy measurements at high temperatures and quasi-hydrostatic pressures of about three gigapascals on previously deformed olivine aggregates and sheared partially molten rocks. For all samples, electrical conductivity is highest when parallel to the direction of prior deformation. The conductivity of highly sheared olivine samples is ten times greater in the shear direction than for undeformed samples. At temperatures above 900 degrees Celsius, a deformed solid matrix with nearly isotropic melt distribution has an electrical anisotropy factor less than five. To obtain higher electrical anisotropy (up to a factor of 100), we propose an experimentally based model in which layers of sheared olivine are alternated with layers of sheared olivine plus MORB or of pure melt. Conductivities are up to 100 times greater in the shear direction than when perpendicular to the shear direction and reproduce stress-driven alignment of the melt. Our experimental results and the model reproduce mantle conductivity-depth profiles for melt-bearing geological contexts. The field data are best fitted by an electrically anisotropic asthenosphere overlain by an isotropic, high-conductivity lowermost lithosphere. The high conductivity could arise from partial melting associated with localized deformation resulting from differential plate velocities relative to the mantle, with subsequent upward melt percolation from the asthenosphere.

Nature ; 495(7442): 499-502, 2013 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-23538832


Melt generated by mantle upwelling is fundamental to the production of new oceanic crust at mid-ocean ridges, yet the forces controlling this process are debated. Passive-flow models predict symmetric upwelling due to viscous drag from the diverging tectonic plates, but have been challenged by geophysical observations of asymmetric upwelling that suggest anomalous mantle pressure and temperature gradients, and by observations of concentrated upwelling centres consistent with active models where buoyancy forces give rise to focused convective flow. Here we use sea-floor magnetotelluric soundings at the fast-spreading northern East Pacific Rise to image mantle electrical structure to a depth of about 160 kilometres. Our data reveal a symmetric, high-conductivity region at depths of 20-90 kilometres that is consistent with partial melting of passively upwelling mantle. The triangular region of conductive partial melt matches passive-flow predictions, suggesting that melt focusing to the ridge occurs in the porous melting region rather than along the shallower base of the thermal lithosphere. A deeper conductor observed east of the ridge at a depth of more than 100 kilometres is explained by asymmetric upwelling due to viscous coupling across two nearby transform faults. Significant electrical anisotropy occurs only in the shallowest mantle east of the ridge axis, where high vertical conductivity at depths of 10-20 kilometres indicates localized porous conduits. This suggests that a coincident seismic-velocity anomaly is evidence of shallow magma transport channels rather than deeper off-axis upwelling. We interpret the mantle electrical structure as evidence that plate-driven passive upwelling dominates this ridge segment, with dynamic forces being negligible.