NMR observation of Tau in Xenopus oocytes

The observation by NMR spectroscopy of microinjected 15N-labelled proteins into Xenopus laevis oocytes might open the way to link structural and cellular biology. We show here that embedding the oocytes into a 20% Ficoll solution maintains their structural integrity over extended periods of time, allowing for the detection of nearly physiological protein concentrations. We use these novel conditions to study the neuronal Tau protein inside the oocytes. Spectral reproducibility and careful comparison of the spectra of Tau before and after cell homogenization is presented. When injecting Tau protein into immature oocytes, we show that both its microtubule association and different phosphorylation events can be detected.     

In‐Situ Nanostructuring and Stabilization of Polycrystalline Copper by an Organic Salt Additive Promotes Electrocatalytic CO2 Reduction to Ethylene

Bridging homogeneous molecular systems with heterogeneous catalysts is a promising approach for the development of new electrodes, combining the advantages of both approaches. In the context of CO₂ electroreduction, molecular enhancement of planar copper electrodes has enabled promising advancement towards high Faradaic efficiencies for multicarbon products. Besides, nanostructured copper electrodes have also demonstrated enhanced performance at comparatively low overpotentials. Herein, we report a novel and convenient method for nanostructuring copper electrodes using N,N′‐ethylene‐phenanthrolinium dibromide as molecular additive. Selectivities up to 70 % for C_≥2 products are observed for more than 40 h without significant change in the surface morphology. Mechanistic studies reveal several roles for the organic additive, including: the formation of cube‐like nanostructures by corrosion of the copper surface, the stabilization of these nanostructures during electrocatalysis by formation of a protective organic layer, and the promotion of C_≥2 products.     

Experimental Requirements for an Efficient Control of Free‐Radical Polymerizations via the Reversible Addition‐Fragmentation Chain Transfer (RAFT) Process

Summary: Reversible addition‐fragmentation chain transfer (RAFT) polymerization is a recent and very versatile controlled radical polymerization technique that has enabled the synthesis of a wide range of macromolecules with well‐defined structures, compositions, and functionalities. The RAFT process is based on a reversible addition‐fragmentation reaction mediated by thiocarbonylthio compounds used as chain transfer agents (CTAs). A great variety of CTAs have been designed and synthesized so far with different kinds of substituents. In this review, all of the CTAs encountered in the literature from 1998 to date are reported and classified according to several criteria : i) the structure of their substituents, ii) the various monomers that they have been polymerized with, and iii) the type of polymerization that has been performed (solution, dispersed media, surface initiated, and copolymerization). Moreover, the influence of various parameters is discussed, especially the CTA structure relative to the monomer and the experimental conditions (temperature, pressure, initiation, CTA/initiator ratio, concentration), in order to optimise the kinetics and the efficiency of the molecular‐weight‐distribution control.

Schematic of the RAFT polymerization.     

Isonitriles as efficient ligands in Suzuki-Miyaura reaction

Isonitrile palladium complexes [(RNC)₂PdCl₂] were prepared and tested in Suzuki reaction of 4-chloroanisol. (AdNC)₂PdCl₂ was found the most effective catalyst and was used in phenylation of several chloro and bromoaromatic substrates.     

Physical–chemical and microstructural study of shells of the Lucina Pectinata species

Journal of Thermal Analysis and Calorimetry - Lucina pectinata, popularly called Lambreta, is a delicacy very consumed in Bahian cuisine. The shell is composed of nacreous layers formed by keratin,...     

The dynamics of entropy in the COVID-19 outbreaks

Nonlinear Dynamics - With the unfolding of the COVID-19 pandemic, mathematical modelling of epidemics has been perceived and used as a central element in understanding, predicting, and governing...     

Semi-analytical Solution for Brine Leakage Through Passive Abandoned Wells Taking Account of Brine Density Differences

Both $\hbox {CO}_{2}$ storage and disposal of waste fluid (e.g., co-produced brine) in deep saline aquifers of sedimentary basins create large scale over-pressurization and tend to displace brine upwards if a vertical connection (e.g., an abandoned well) is present. This raises groundwater pollution issues of brine intrusion into shallower potable water aquifers. When saline brine from the deep aquifer is displaced upwards it lifts and replaces the a priori less saline, less dense water initially filling the connection, resulting in a weight increase that counters leakage. This article presents and explains an innovative semi-analytical solution to this problem of leakage between two aquifers connected by a passive well (represented by a porous column and/or an open wellbore) taking account of the effect of the density difference between lifting and lifted brines during both upward and downward flow. It is based on the linearization of brine density profiles against depth and on two improvements made to the approximate evaluation of convolution products introduced in Nordbotten et al. (Water Resour Res 40:W04204, 2004) for calculation of the pressurization induced by transient flows in open aquifers. The comparison with numerical simulations shows good agreement of results. Since the solution uses time discretization but no spatial grid, computation time is reduced by 3–4 orders of magnitude compared to numerical resolution. It does, however, require considering homogeneous aquifers of constant thickness and brine properties.     

Feasibility of particle image velocimetry in vegetative fire spread experiments

This study is part of an ongoing effort to improve the understanding of mechanisms that control the spread of fires with a focus on the turbulent flow modified by the flame front. A large-scale PIV system was used to measure the flow field inside and in the vicinity of a flame front spreading across a bed of fuel in an open environment. The vegetative fuel consisted of a 10-m-long and 5-m-wide bed of excelsior (1?kg/m2 fuel load) leading to a nearly 1.5-m-high flame front. The velocity field was investigated in a measurement region about 1.5?m high and 2?m long. In such a configuration, a 450-mJ laser source was used to generate the light sheet, and the flow was seeded using zirconium oxide particles (ZrO₂). The PIV measurements in the presence of flame were improved by the use of a liquid crystal shutter in front of the PIV camera, allowing very short exposure times and eliminating the flame trace in the tomographic pictures. Despite the variability of the external conditions, leading to a difficult seeding over the whole PIV area, the present study shows the feasibility of the optical method of fluid visualization in the field. The measurements of the velocity fields show some features of the dynamics of fire plumes. This preliminary study demonstrates the feasibility of the method in the open, but some strong efforts to improve the seeding of the flow must be made.     

Pyruvate cellular uptake and enzymatic conversion probed by dissolution DNP‐NMR: the impact of overexpressed membrane transporters

Pyruvate membrane crossing and its lactate dehydrogenase‐mediated conversion to lactate in cells featuring different levels of expression of membrane monocarboxylate transporters (MCT4) were probed by dissolution dynamic nuclear polarization‐enhanced NMR. Hyperpolarized ¹³C‐1‐labeled pyruvate was transferred to suspensions of rodent tumor cell carcinoma, cell line 39. The pyruvate‐to‐lactate conversion rate monitored by dissolution dynamic nuclear polarization‐NMR in carcinoma cells featuring native MCT4 expression level was lower than the rate observed for cells in which the human MCT4 gene was overexpressed. The enzymatic activity of lactate dehydrogenase was also assessed in buffer solutions, following the real‐time pyruvate‐to‐lactate conversion speeds at different enzyme concentrations. Copyright © 2016 John Wiley & Sons, Ltd.     

Ionic conducting membranes based on new sulfonated poly(arylene ether ketone)s for fuel cell applications

The synthesis and characterization of new di‐ and tetra‐sulfonated ether diketone monomers are described. From these monomers, a wide series of sulfonated poly(arylene ether ketone)s (SPAEK) are synthesized by varying the sulfonic acid repartition along the polymer backbones. Their chemical structures are thoroughly characterized by NMR. From these polymers tough membranes are obtained from solution casting method and their water uptake, ionic conductivity, and water/gas permeation properties are determined and compared with those of Nafion membrane. Preliminary fuel cell tests show that SPAEK membranes are promising candidates for fuel cell application. This work brings new insights concerning the beneficial effects of introducing densely sulfonated monomers in a polyarylether macromolecular structure along with fluorinated groups improving conductivity while reducing unwanted excessive swelling. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 771–777