Chlorine redox chemistry is not rare in biology

Chlorine is abundant in cells and biomolecules, yet the biology of chlorine oxidation and reduction is poorly understood. Some bacteria encode the enzyme chlorite dismutase (Cld), which detoxifies chlorite (CIO2-) by converting it to chloride (Cl-) and molecular oxygen (O2). Cld is highly specific for chlorite and aside from low hydrogen peroxide activity has no known alternative substrate. Here, we reasoned that because chlorite is an intermediate oxidation state of chlorine, Cld can be used as a biomarker for oxidized chlorine species in microorganisms and microbial habitats. Cld was abundant in metagenomes from soils and freshwater to water treatment systems. About 5% of bacterial and archaeal genera contain an organism encoding Cld in its genome, and within some genera Cld is nearly conserved. Cld has been subjected to extensive horizontal gene transfer, suggesting selection by chlorite is episodic yet strong. Cld was also used as a biomarker to predict genes related to chlorine redox chemistry. Genes found to have a genetic association with Cld include known genes for responding to reactive chlorine species and uncharacterized genes for transporters, regulatory elements, and putative oxidoreductases that present targets for future research. Cld was repeatedly co-located in genomes with genes for enzymes that can inadvertently reduce perchlorate (CIO4-) or chlorate (CIO3-), confirming that in nature (per)chlorate reduction does not only occur in specialized anaerobic respiratory metabolisms. The presence of Cld in genomes of obligate aerobes without such enzymes suggested that chlorite, like hypochlorous acid (HOCl), might be formed by oxidative processes within natural habitats. In summary, the comparative genomics of Cld has provided an atlas for a deeper understanding of chlorine oxidation and reduction reactions that are an underrecognized feature of biology.

SOME FEATURES OF DIFFERENTIATION OF CONCENTRATION OF DIENE CONJUGATES IN BLOOD SERUM AND TISSUE OF RATS

One of the mechanisms for maintaining homeostasis in the body is lipid peroxidation (LPO). The influence of external and internal factors affecting the body can change the dynamics of LPO processes, causing numerous disorders in the functioning of organ systems. The dynamics of LPO processes in the early stages can be estimated from the change in the concentration of intermediate oxidation products - diene conjugates (DC). The purpose of our study was to identify the features of the differentiation of the distribution of the concentration of diene conjugates in the blood serum and tissues of white outbred rats. New results of nonparametric correlation analysis are presented to assess the relationship of the distribution of the concentration of diene conjugates in the blood serum and tissues of white outbred rats.

Formation and sink of glyoxal and methylglyoxal in a polluted subtropical environment: observation-based photochemical analysis and impact evaluation

The dicarbonyls, glyoxal (Gly) and methylglyoxal (Mgly) have been recognized as important precursors of secondary organic aerosols (SOAs) through the atmospheric heterogeneous process. In this study, field measurement was conducted at a receptor site in the Pearl River Delta (PRD) region in south China, and an observation based photochemical box model was subsequently applied to investigate the production and evolution of Gly and Mgly as well as their contributions to SOA formation. The model was coupled with a detailed gas-phase oxidation mechanism of volatile organic compounds (VOCs) (i.e., MCM v3.2), heterogeneous processes of Gly and Mgly (i.e., reversible partitioning in aqueous phase, irreversible volume reactions and irreversible surface uptake processes), and the gas-particle partitioning of oxidation products. The results suggested that without considering the heterogeneous processes of Gly and Mgly on aerosol surfaces would overpredict the mixing ratios of Gly and Mgly by factors of 3.3 and 3.5 compared to the observed levels. The agreement between observation and simulation improved significantly when the irreversible uptake and the reversible partitioning were incorporated into the model, which in total contributed ~ 72 and ~ 73 % to the destruction of Gly and Mgly, respectively. Further analysis on the photochemical budget of Gly and Mgly showed that the oxidation of aromatics by the OH radical was the major pathway producing Gly and Mgly, followed by degradation of alkynes and alkenes. Furthermore, based on the improved model mechanism, the contributions of VOCs oxidation to SOA formed from gas-particle partitioning (SOAgp) and from heterogeneous processes of Gly and Mgly (SOAhet) were also quantified. It was found that o-xylene was the most significant contributor to SOAgp formation (~ 29 %), while m/p-xylene and toluene made dominant contributions to SOAhet formation. Overall the heterogeneous processes of Gly and Mgly can explain ~ 21 % of SOA mass in the PRD region. The results of this study demonstrated the important roles of heterogeneous processes of Gly and Mgly in SOA formation, and highlighted the need for a better understanding of the evolution of intermediate oxidation products.

Biodegradation of a phosphorus compounds by the culture of black aspergill

The biological degradation of white phosphorus, which is being studied by our team is without a doubt a phenomenon of scientific novelty and practical significance. In a decade of studying this phenomenon, we have achieved significant results. However, the field of application of white and yellow phosphorus is rather a narrow one, and this imposes a limitation on the applicability of our method for the neutralization of industrial wastes. Accordingly, an interesting and important path of focus is to expand the spectrum of substances neutralized by the microbial cultures studied by our team. It is thus logical to commence such a major study with phosphorus compounds, since fungal cultures were adapted for the biodegradation of substances containing this element. In this regard, it should be pointed out that, white phosphorus cannot be metabolized to phosphate in one stage; metabolites are formed with intermediate oxidation states of phosphorus. Therefore, it can be assumed that microorganisms that neutralize white phosphorus should be capable of biodegradation of a whole spectrum of phosphorus compounds. We tested this hypothesis experimentally. It was uncovered that Aspergillus niger AM1 posseses the ability to use red phosphorus, triamide of phosphoric acid, phosphomolybdic acid, substituted dithiophosphate and organophosphorus matter as sources of phosphorus. In addition, in the present work, we describe attempts made to increase the concentration of white phosphorus in the culture medium to values above 1%. To do this, we added olive oil (a solvent in which white phosphorus is relatively soluble) to the culture medium. It turned out that in the presence of this component, the minimum inhibitory concentration of white phosphorus drops abruptly.

Mobility of dissolved palladium and platinum species under water-rock interaction in chloride media: modeling of PGE behavior under interaction of oceanic serpentinites with sea water derivates

To elucidate the possibility of PGE transfer by highly-salt chloride solutions, the palladium and platinum behavior was simulated in the conditions of low-temperature hydrothermal transformation of serpentinites of the oceanic crust. In dynamic water-rock experiments using columns filled with crushed ultrabasic rocks of the ocean floor (harzburgite serpentinites of mid-oceanic ridges with different degrees of carbonatization), it is established that the efficiency of palladium transfer depends on the alteration (carbonatization) degree of peridotites and under the experimental conditions is 80–100%. It is assumed that the transport of palladium occurs as a result of the formation of a strong complex compound with thiosulfate ion, which is an intermediate oxidation product in the “sulphide-sulfate” system. Platinum, hydrolyzed at approximately neutral pH and not forming compounds with thiosulfate ion, is completely retained by serpentinites, possibly due to sorption interactions with silicates. Thus, the higher mobility of palladium during the low- temperature transformation of abyssal peridotites and the dependence of the character of its distribution in the studied rocks on the processes of serpentinization and carbonatization have been confirmed.

The study of the phase composition of the products of electrochemical oxidation of sulfide granules of the system Cu1.96S–Ni3S2–Cu–Ni

The crystallization rate of copper and nickel sulfides influences on the phase formation processes. The high crystallization rate (about 103 degrees/s), achieved through granulation of the sulfide copper-nickel melt, leads to the stabilization of non-stoichiometric phases, the formation of ultrafine structures, which are grains and partial dissolution of the metal component in the sulfide. The structure of the granules is formed by nickel sulfide (Cu1.96S) phases in the form of dendritic inclusions of 2-20 µm in size in the nickel sulfide phase (Ni3S2). According to the phase diagram of the state of Cu – Ni – S, a solid solution of Cu – Ni may be present in the composition of eutectic compounds with copper and nickel sulphides. The electrochemical oxidation of copper and nickel sulfides in a solution of sulfuric acid occurs through a series of successive phase transformations described in the work, during which the conversion of sulfides occurs in intermediate oxidation states oxidizing to the elemental state: Cu1.96S → Cu1.8S → Cu1.75S → CuS → S; Ni3S2 → NiS → S. The non-stoichiometric composition of compounds suggests the presence of excessive or deficient sulfur and metal contents in the crystal lattice, which can affect the mechanism and sequence of phase transformations during the electrochemical oxidation of sulfide granules. Dissolution occurs not only on the surface of the granules, but also along the grain boundaries. The leached areas form capillaries inside the granules, through which electrolyte enters the electrochemical reactions. Porous sulfur sulfide sludge forms on the surface of the granules. The phase composition of the sludge was studied. The main phase components of poorly soluble products are nickel granules Ni3+хS2–Cu2-хS.