Microbes: A potential tool for selenium biofortification

Selenium (Se) is a component of many enzymes and indispensable for human health due to its characteristics of reducing oxidative stress and enhancing immunity. Human beings take Se mainly from Se-containing crops. Taking measures to biofortify crops with Se may lead to improved public health. Se accumulation in plants mainly depends on the content and bioavailability of Se in soil. Beneficial microbes may change the chemical form and bioavailability of Se. This review highlights the potential role of microbes in promoting Se uptake and accumulation in crops and the related mechanisms. The potential approaches of microbial enhancement of Se biofortification can be summarized in the following four aspects: (1) microbes alter soil properties and impact the redox chemistry of Se to improve the bioavailability of Se in soil; (2) beneficial microbes regulate root morphology and stimulate the development of plants through the release of certain secretions, facilitating Se uptake in plants; (3) microbes upregulate the expression of certain genes and proteins that are related to Se metabolism in plants; (4) the inoculation of microbes give rise to the generation of certain metabolites in plants contributing to Se absorption. Considering the ecological safety and economic feasibility, microbial enhancement is a potential tool for Se biofortification. For further study, the recombination and establishment of synthesis microbes is of potential benefit in Se-enrichment agriculture.

Mitochondrial energetics with transmembrane electrostatically localized protons: do we have a thermotrophic feature?

Transmembrane electrostatically localized protons (TELP) theory has been recently recognized as an important addition over the classic Mitchell’s chemiosmosis; thus, the proton motive force (pmf) is largely contributed from TELP near the membrane. As an extension to this theory, a novel phenomenon of mitochondrial thermotrophic function is now characterized by biophysical analyses of pmf in relation to the TELP concentrations at the liquid-membrane interface. This leads to the conclusion that the oxidative phosphorylation also utilizes environmental heat energy associated with the thermal kinetic energy (kBT) of TELP in mitochondria. The local pmf is now calculated to be in a range from 300 to 340 mV while the classic pmf (which underestimates the total pmf) is in a range from 60 to 210 mV in relation to a range of membrane potentials from 50 to 200 mV. Depending on TELP concentrations in mitochondria, this thermotrophic function raises pmf significantly by a factor of 2.6 to sixfold over the classic pmf. Therefore, mitochondria are capable of effectively utilizing the environmental heat energy with TELP for the synthesis of ATP, i.e., it can lock heat energy into the chemical form of energy for cellular functions.

A Study on the Presence of Aflatoxin M1 in Cow’s Milk in Jiroft

Background and Aims: Cow's milk is a daily staple food for many individuals that can be contaminated with many toxins such as aflatoxin M1 (AFM1). AFM1 is a chemical form of the aflatoxin B1 produced by some species of Aspergillus genus like A. ochraceus, A. flavus, A. nomius, and A. parasiticus that can contaminate feed and forage cattle. This toxin enters into the milk after eating contaminated feed by cows. AFM1 can cause various dangerous diseases such as cancer and immune deficiency in humans. The present study is aimed to investigate the level of AFM1 in cow's milk in Jiroft, Kerman Province, Iran. Materials and Methods: A total of 90 cow’s milk samples were collected in spring and summer 2019 from available stores in Jiroft city. Enzyme-linked immunosorbent assay was used to measure AFM1 in all cow’s milk samples.Results: In the present study, AFM1 was found in 88 (97.8%) milk samples with a range of 0.2-90.62 ppt (mean, 20.07±24.46 ppt). AFM1 concentrations exceeded 50 ppt (maximum tolerance level of AFM1 in the European Union) was seen in 12 (13.3%) samples. Conclusions: The results of this study showed the presence of AFM1 in cow's milk in Jiroft city. So, in this region, many people are exposed to dangerous diseases such as cancer due to the consumption of milk contaminated with AFM1.

Selenium Transport Mechanism via Selenoprotein P—Its Physiological Role and Related Diseases

Selenoprotein P (SELENOP) is selenium (Se)-containing protein in plasma, which is primarily produced in the liver. The “P” in SELENOP originated from the presence in plasma. SELENOP contains selenocysteine, a cysteine analog containing Se instead of sulfur. SELENOP is a multi-functional protein to reduce phospholipid hydroperoxides and to deliver Se from the liver to other tissues, such as those of the brain and testis, playing a pivotal role in Se metabolism and antioxidative defense. Decrease in SELENOP causes various dysfunctions related to Se deficiency and oxidative stress, while excessive SELENOP causes insulin resistance. This review focuses on the Se transport system of SELENOP, particularly its molecular mechanism and physiological role in Se metabolism. Furthermore, the chemical form of Se and its biological meaning is discussed.

Plant and Algal PSII–LHCII Supercomplexes: Structure, Evolution and Energy Transfer

Photosynthesis is the process conducted by plants and algae to capture photons and store their energy into a chemical form. The light-harvesting, excitation transfer, charge separation, and electron transfer in photosystem II (PSII) are the critical initial reactions of photosynthesis and thereby largely determine its overall efficiency. In this review, we outline the rapidly accumulating knowledges about the architectures and assemblies of plant and green algal PSII–light harvesting complex II (LHCII) supercomplexes with a particular focus on new insights provided by the recent high-resolution cryo-electron microscopy (cryo-EM) map of the supercomplexes from a green alga Chlamydomonas reinhardtii. We make pair-wise comparative analyses between the supercomplexes from plants and green algae to gain insights about the evolution of the PSII–LHCII supercomplexes involving the peripheral small PSII subunits that might have been acquired during the evolution, and about the energy transfer pathways that define their light-harvesting and photoprotective properties.

Separation of Zr from Zr-2.5Nb by Electrorefining in LiCl-KCl for Volumetric Decontamination of CANDU Pressure Tube

This study presents an experimental investigation on Zr separation from Zr-2.5Nb by anode potentiostatic electrorefining in LiCl-KCl-ZrCl4 0.5 wt. % at 773 K for irradiated CANDU pressure tube decontamination. By the ORIGEN-2 code calculation, radioactive characteristics were investigated to show that Nb-94 was the most significant radionuclide with an aspect of waste level reduction by electrorefining. Three electrorefining tests were performed by fixing the applied potential as −0.9 V (vs. Ag/AgCl 1 wt. %) at the anode to dissolve only Zr. A cathode basket was installed to collect detached deposits from the cathode. Electrorefining results showed Zr was deposited on the cathode with a small amount of Nb and other alloying elements. The chemical form of the cathode deposits was shown to be only Zr metal or a mixture of Zr metal and ZrCl, depending on the experimental conditions related to the surface area ratio of the cathode to the anode. It was determined that the Zr metal reduction at the cathode was attributed to the two-step reduction reaction of Zr4+/ZrCl and ZrCl/Zr.