Sodium Accumulation in Infected Cells and Ion Transporters Mistargeting in Nodules of Medicago truncatula: Two Ugly Items That Hinder Coping with Salt Stress Effects.

The maintenance of intracellular nitrogen-fixing bacteria causes changes in proteins' location and in gene expression that may be detrimental to the host cell fitness. We hypothesized that the nodule's high vulnerability toward salt stress might be due to alterations in mechanisms involved in the exclusion of Na+ from the host cytoplasm. Confocal and electron microscopy immunolocalization analyses of Na+/K+ exchangers in the root nodule showed the plasma membrane (MtNHX7) and endosome/tonoplast (MtNHX6) signal in non-infected cells; however, in mature infected cells the proteins were depleted from their target membranes and expelled to vacuoles. This mistargeting suggests partial loss of the exchanger's functionality in these cells. In the mature part of the nodule 7 of the 20 genes encoding ion transporters, channels, and Na+/K+ exchangers were either not expressed or substantially downregulated. In nodules from plants subjected to salt treatments, low temperature-scanning electron microscopy and X-ray microanalysis revealed the accumulation of 5-6 times more Na+ per infected cell versus non-infected one. Hence, the infected cells' inability to withstand the salt may be the integral result of preexisting defects in the localization of proteins involved in Na+ exclusion and the reduced expression of key genes of ion homeostasis, resulting in premature senescence and termination of symbiosis.

Synthesis, structure and properties of layered Pr2MoO6-based oxymolybdates doped with Mg.

Undoped and Mg-doped Pr2MoO6 oxymolybdate polycrystals and single crystals have been prepared by solid-state reactions and flux growth. The compounds have been characterized by powder X-ray diffraction, energy-dispersive spectroscopy, inductively coupled plasma mass spectrometry, scanning transmission electron microscopy, single crystal X-ray structure analysis, differential scanning calorimetry and thermogravimetry. The (MgO)x(Pr2O3)y(MoO3)z (x + y + z = 1) solid solution series has been shown to extend to x = 0.03. The structure of the Mg-doped Pr2MoO6 single crystals can be represented as superimposed lattices of the main matrix (Pr2MoO6) and lattices in which Mo atoms are partially replaced by Mg. The incorporation of Mg atoms into the structure of Pr2MoO6 results in the disordering of the praseodymium and oxygen lattices. Both the polycrystalline and single-crystal Mg-doped samples are hygroscopic.

Electroconductive PEDOT:PSS-based hydrogel prepared by freezing-thawing method.

Biopolymer-based composition with adding of conductive polymer poly-(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT PSS) was made by mixing of iota-carrageenan (CRG), polyvinyl alcohol (PVA) and PEDOT PSS followed by freezing/thawing cycles. The method is environmentally friendly and based on the formation of polymer matrix upon of mixing CRG, PVA and PEDOT PSS and formation of porous physical gel due to freezing/thawing cycles. It is necessary to mention that all components are well-known as biocompatible materials. The resulting material is stable in water and also has swelling capability both in distilled water and physiological solutions. Structure of material was characterized by means of X-ray diffraction, optical and electron microscopy. Electrophysical investigations also were performed. The conductivity of the gel immersed in distilled water is comparable with the dry gel value and close to 0.01 [S/cm].

Synthesis of a Bulk Ti4SiC3 MAX Phase by Reduction of TiO2 with SiC.

The bulk MAX phase Ti4SiC3 was first synthesized with a yield of 86% by a long-time thermal treatment of TiO2 and SiC powder mixture with a molar ratio of 2:3 at 1600 °C under vacuum conditions. It was found that the appearance of Ti4SiC3 was preceded by the formation of TiC and Ti3SiC2 as a result of the following reactions: (1) combined carbothermic and silicothermic reduction of TiO2 to TiC accompanied by evolution of SiO and CO gases; (2) silicidation of TiC with gaseous SiO, leading to the growth of Ti3SiC2. It was suggested that, apart from TiC and Ti3SiC2 solids, sublimed gaseous species such as Ti, Si, Si2C, SiC2, etc., could take part in the Ti4SiC3 formation that occurred in the next stage. The crystal structure of synthesized Ti4SiC3 was refined by X-ray diffraction Rietveld analysis and confirmed by high-resolution scanning transmission electron microscopy. The measured structural characteristics of bulk Ti4SiC3 are in good agreement with those predicted by ab initio calculations reported in the literature.