Солевой состав и физико-химические процессы в объеме гранул удобрений на стадии хранения

The results of studies of the salt composition and physicochemical processes occurring in separate layers (volume) of granules of complex fertilizers based on ammonium phosphates at the stage of storage in the interval up to 180 days are given. The data of chemical and physicochemical studies, as well as the analysis of microphotographs and element-by-element composition of granules showed the absence of a significant gradient of concentrations of individual components in the volume of granules when they arrive from the technological process. The course of secondary conversion processes in the volume of granules during 3 and 6 months of storage was established, leading, in particular, to a significant decrease in the content of ammonium dihydrogen phosphate in the product from 25.41-27.91 to 1.23-3.25 % and urea, as well as the formation of newdouble salts and adducts: (Kχ,(NH4)1-χ)•H2PO4, CO(NH2)2•NH4Cl. The change in the phase composition of the product during long-term storage and the associated chemical interaction between the layers of individual granules is accompanied by an increase in caking. It is established that during 3 and 6 months of storage, the content of the liquid phase increases, which leads to a partial decrease in the content of individual components. The most active process of sorption of water vapor proceeds in the 1st (outer layer) of granules, while fluctuations in its content in deeper layers are within the margin of error. The dependence of the caking of the product on the type of injected nitrogen-containing component and the forms of nitrogen content in it has been established. The results of the study made it possible to recommend ways to reduce caking and improve the physical and mechanical properties of complex fertilizers during their storage and transportation: increasing the molar ratio at the ammoniation stage to values corresponding to the formation of diammonium phosphate; increasing the ratio of ammonium to the amide form of nitrogen; an increase in the proportion of granular urea in the composition of the fertilizer, followed by the complete exclusion of prilled urea.Приведены результаты исследований солевого состава и физико-химических процессов, протекающих в отдельных слоях (объеме) гранул комплексных удобрений на основе фосфатов аммония на стадии складского хранения до 180 сут. Данные химических и физико-химических исследований, а также анализ микрофотографий и поэлементного состава показал отсутствие значимого градиента концентраций отдельных компонентов в объеме гранул удобрений при их поступлении на склад из технологического процесса. Установлено протекание вторичных конверсионных процессов в объеме гранул в течение 3- и 6-месячного хранения, приводящих, в частности, к существенному снижению содержания в продукте дигидрофосфата аммония с 25,41-27,91 до 1,23-3,25 мас.% и карбамида, а также образованию новых двойных солей и аддуктов: (Kχ(NH4)1-χ)•H2PO4, CO(NH2)2•NH4Cl. Изменение фазового состава продукта в процессе длительного хранения и связанное с этим химическое взаимодействие между слоями отдельных гранул сопровождается увеличением слеживаемости. Установлена зависимость слеживаемости продукта от вида вводимого азотсодержащего компонента и форм содержания в нем азота. Результаты исследования позволили рекомендовать пути снижения слеживаемости и улучшения физико-механических свойств комплексных удобрений, в частности, повышение мольного соотношения на стадии аммонизации до значений, соответствующих образованию диаммонийфосфата; увеличение соотношения аммонийной к амидной форме азота; увеличение доли гранулированного карбамида в составе удобрения с последующим полным исключением приллированного карбамида

A role for the Saccharomyces cerevisiae ABCF protein New1 in translation termination/recycling

Translation is controlled by numerous accessory proteins and translation factors. In the yeast Saccharomyces cerevisiae, translation elongation requires an essential elongation factor, the ABCF ATPase eEF3. A closely related protein, New1, is encoded by a non-essential gene with cold sensitivity and ribosome assembly defect knock-out phenotypes. Since the exact molecular function of New1 is unknown, it is unclear if the ribosome assembly defect is direct, i.e. New1 is a bona fide assembly factor, or indirect, for instance due to a defect in protein synthesis. To investigate this, we employed yeast genetics, cryo-electron microscopy (cryo-EM) and ribosome profiling (Ribo-Seq) to interrogate the molecular function of New1. Overexpression of New1 rescues the inviability of a yeast strain lacking the otherwise strictly essential translation factor eEF3. The structure of the ATPase-deficient (EQ2) New1 mutant locked on the 80S ribosome reveals that New1 binds analogously to the ribosome as eEF3. Finally, Ribo-Seq analysis revealed that loss of New1 leads to ribosome queuing upstream of 3'-terminal lysine and arginine codons, including those genes encoding proteins of the cytoplasmic translational machinery. Our results suggest that New1 is a translation factor that fine-tunes the efficiency of translation termination or ribosome recycling

Физико-химические особенности кислотного разложения доломита

The results of studies of the physico-chemical regularities of the acid decomposition of magnesium-containing raw materials are presented and the optimal technological mode of the individual stages of obtaining magnesium sulfate is determined. It has been established that the process of obtaining magnesium sulfate based on dolomite includes the following stages: decomposition of magnesium-containing raw materials with sulfuric acid; filtration of the resulting suspension with separation of calcium sulfate and insoluble residue and subsequent washing; crystallization and separation of magnesium sulfate; drying the target product. The main technological parameters that determine the stage of sulfuric acid decomposition are: the rate of sulfuric acid, the duration of decomposition, the method and procedure for introducing reagents, the content of magnesium sulfate in the liquid phase of the suspension. In this case, the concentration of sulfuric acid cannot be considered as the main technological parameter, since its numerical value is selected depending on the value of the final content of magnesium sulfate in the liquid phase, which in turn is determined by its solubility in water. It has been proven that the use of a flocculant at the decomposition stage provides an increased filtration rate, improved filtration performance, as well as keeping the filter cloth uncontaminated. The results of chemical and X-ray phase analyzes confirmed that magnesium sulfate obtained from domestic dolomite raw materials in its composition corresponds to magnesium sulfate obtained from foreign types of magnesium-containing raw materials - magnesite, brucite - and fully complies with the requirements of TU 2141016-32496445-00 “Magnesium sulfate”. Приведены результаты исследований физико-химических закономерностей кислотного разложения магнийсодержащего сырья и определен оптимальный технологический режим отдельных стадий получения сульфата магния. Установлено, что процесс получения сульфата магния на основе доломита включает следующие стадии: разложение магнийсодержащего сырья серной кислотой; фильтрацию образующейся суспензии с отделением сульфата кальция и нерастворимого остатка с последующей промывкой; кристаллизацию и выделение сульфата магния; сушку целевого продукта. Основными технологическими параметрами, определяющими стадию сернокислотного разложения являются: норма серной кислоты, продолжительность разложения, способ и порядок введения реагентов, содержание сульфата магния в жидкой фазе суспензии. При этом концентрация серной кислоты не может рассматриваться в качестве основного технологического параметра, поскольку ее численное значение выбирается в зависимости от величины конечного содержания сульфата магния в жидкой фазе, которое в свою очередь определяется его растворимостью в воде. Доказано, что применение флокулянта на стадии разложения обеспечивает повышенную скорость фильтрации, улучшение показателей фильтрата, а также сохранение фильтровальной ткани в незагрязненном виде. Результаты химического и рентгенофазового анализов подтвердили, что сульфат магния, полученный из отечественного сырья доломита, по своему составу аналогичен сульфату магния, полученному из зарубежных видов магнийсодержащего сырья - магнезита, брусита, и полностью соответствует требованиям ТУ 2141-016-32496445-00 «Магний сернокислый»

Development of a general calibration model and long-term performance evaluation of low-cost sensors for air pollutant gas monitoring

Assessing the intracity spatial distribution and temporal variability in air quality can be facilitated by a dense network of monitoring stations. However, the cost of implementing such a network can be prohibitive if traditional high-quality, expensive monitoring systems are used. To this end, the Real-time Affordable Multi-Pollutant (RAMP) monitor has been developed, which can measure up to five gases including the criteria pollutant gases carbon monoxide (CO), nitrogen dioxide (NO2), and ozone (O3), along with temperature and relative humidity. This study compares various algorithms to calibrate the RAMP measurements including linear and quadratic regression, clustering, neural networks, Gaussian processes, and hybrid random forest–linear regression models. Using data collected by almost 70 RAMP monitors over periods ranging up to 18 months, we recommend the use of limited quadratic regression calibration models for CO, neural network models for NO, and hybrid models for NO2 and O3 for any low-cost monitor using electrochemical sensors similar to those of the RAMP. Furthermore, generalized calibration models may be used instead of individual models with only a small reduction in overall performance. Generalized models also transfer better when the RAMP is deployed to other locations. For long-term deployments, it is recommended that model performance be re-evaluated and new models developed periodically, due to the noticeable change in performance over periods of a year or more. This makes generalized calibration models even more useful since only a subset of deployed monitors are needed to build these new models. These results will help guide future efforts in the calibration and use of low-cost sensor systems worldwide.</p

GTP-dependent structural rearrangement of the eRF1:eRF3 complex and eRF3 sequence motifs essential for PABP binding

Translation termination in eukaryotes is governed by the concerted action of eRF1 and eRF3 factors. eRF1 recognizes the stop codon in the A site of the ribosome and promotes nascent peptide chain release, and the GTPase eRF3 facilitates this peptide release via its interaction with eRF1. In addition to its role in termination, eRF3 is involved in normal and nonsense-mediated mRNA decay through its association with cytoplasmic poly(A)-binding protein (PABP) via PAM2-1 and PAM2-2 motifs in the N-terminal domain of eRF3. We have studied complex formation between full-length eRF3 and its ligands (GDP, GTP, eRF1 and PABP) using isothermal titration calorimetry, demonstrating formation of the eRF1:eRF3:PABP:GTP complex. Analysis of the temperature dependence of eRF3 interactions with G nucleotides reveals major structural rearrangements accompanying formation of the eRF1:eRF3:GTP complex. This is in contrast to eRF1:eRF3:GDP complex formation, where no such rearrangements were detected. Thus, our results agree with the established active role of GTP in promoting translation termination. Through point mutagenesis of PAM2-1 and PAM2-2 motifs in eRF3, we demonstrate that PAM2-2, but not PAM2-1 is indispensible for eRF3:PABP complex formation

An ancient family of SelB elongation factor-like proteins with a broad but disjunct distribution across archaea

<p>Abstract</p> <p>Background</p> <p>SelB is the dedicated elongation factor for delivery of selenocysteinyl-tRNA to the ribosome. In archaea, only a subset of methanogens utilizes selenocysteine and encodes archaeal SelB (aSelB). A SelB-like (aSelBL) homolog has previously been identified in an archaeon that does not encode selenosysteine, and has been proposed to be a pyrrolysyl-tRNA-specific elongation factor (EF-Pyl). However, elongation factor EF-Tu is capable of binding archaeal Pyl-tRNA in bacteria, suggesting the archaeal ortholog EF1A may also be capable of delivering Pyl-tRNA to the ribosome without the need of a specialized factor.</p> <p>Results</p> <p>We have phylogenetically characterized the aSelB and aSelBL families in archaea. We find the distribution of aSelBL to be wider than both selenocysteine and pyrrolysine usage. The aSelBLs also lack the carboxy terminal domain usually involved in recognition of the selenocysteine insertion sequence in the target mRNA. While most aSelBL-encoding archaea are methanogenic Euryarchaea, we also find aSelBL representatives in Sulfolobales and Thermoproteales of Crenarchaea, and in the recently identified phylum Thaumarchaea, suggesting that aSelBL evolution has involved horizontal gene transfer and/or parallel loss. Severe disruption of the GTPase domain suggests that some family members may employ a hitherto unknown mechanism of nucleotide hydrolysis, or have lost their GTPase ability altogether. However, patterns of sequence conservation indicate that aSelBL is still capable of binding the ribosome and aminoacyl-tRNA.</p> <p>Conclusions</p> <p>Although it is closely related to SelB, aSelBL appears unlikely to either bind selenocysteinyl-tRNA or function as a classical GTP hydrolyzing elongation factor. We propose that following duplication of aSelB, the resultant aSelBL was recruited for binding another aminoacyl-tRNA. In bacteria, aminoacylation with selenocysteine is essential for efficient thermodynamic coupling of SelB binding to tRNA and GTP. Therefore, change in tRNA specificity of aSelBL could have disrupted its GTPase cycle, leading to relaxation of selective pressure on the GTPase domain and explaining its apparent degradation. While the specific role of aSelBL is yet to be experimentally tested, its broad phylogenetic distribution, surpassing that of aSelB, indicates its importance.</p

A Computational Study of Elongation Factor G (EFG) Duplicated Genes: Diverged Nature Underlying the Innovation on the Same Structural Template

BACKGROUND: Elongation factor G (EFG) is a core translational protein that catalyzes the elongation and recycling phases of translation. A more complex picture of EFG's evolution and function than previously accepted is emerging from analyzes of heterogeneous EFG family members. Whereas the gene duplication is postulated to be a prominent factor creating functional novelty, the striking divergence between EFG paralogs can be interpreted in terms of innovation in gene function. METHODOLOGY/PRINCIPAL FINDINGS: We present a computational study of the EFG protein family to cover the role of gene duplication in the evolution of protein function. Using phylogenetic methods, genome context conservation and insertion/deletion (indel) analysis we demonstrate that the EFG gene copies form four subfamilies: EFG I, spdEFG1, spdEFG2, and EFG II. These ancient gene families differ by their indispensability, degree of divergence and number of indels. We show the distribution of EFG subfamilies and describe evidences for lateral gene transfer and recent duplications. Extended studies of the EFG II subfamily concern its diverged nature. Remarkably, EFG II appears to be a widely distributed and a much-diversified subfamily whose subdivisions correlate with phylum or class borders. The EFG II subfamily specific characteristics are low conservation of the GTPase domain, domains II and III; absence of the trGTPase specific G2 consensus motif "RGITI"; and twelve conserved positions common to the whole subfamily. The EFG II specific functional changes could be related to changes in the properties of nucleotide binding and hydrolysis and strengthened ionic interactions between EFG II and the ribosome, particularly between parts of the decoding site and loop I of domain IV. CONCLUSIONS/SIGNIFICANCE: Our work, for the first time, comprehensively identifies and describes EFG subfamilies and improves our understanding of the function and evolution of EFG duplicated genes

Mechanism of eIF6 release from the nascent 60S ribosomal subunit.

SBDS protein (deficient in the inherited leukemia-predisposition disorder Shwachman-Diamond syndrome) and the GTPase EFL1 (an EF-G homolog) activate nascent 60S ribosomal subunits for translation by catalyzing eviction of the antiassociation factor eIF6 from nascent 60S ribosomal subunits. However, the mechanism is completely unknown. Here, we present cryo-EM structures of human SBDS and SBDS-EFL1 bound to Dictyostelium discoideum 60S ribosomal subunits with and without endogenous eIF6. SBDS assesses the integrity of the peptidyl (P) site, bridging uL16 (mutated in T-cell acute lymphoblastic leukemia) with uL11 at the P-stalk base and the sarcin-ricin loop. Upon EFL1 binding, SBDS is repositioned around helix 69, thus facilitating a conformational switch in EFL1 that displaces eIF6 by competing for an overlapping binding site on the 60S ribosomal subunit. Our data reveal the conserved mechanism of eIF6 release, which is corrupted in both inherited and sporadic leukemias.Supported by a Federation of European Biochemical Societies Long term Fellowship (to FW), Specialist Programme from Bloodwise [12048] (AJW), the Medical Research Council [MC_U105161083] (AJW) and [U105115237] (RRK), Wellcome Trust strategic award to the Cambridge Institute for Medal Research [100140], Tesni Parry Trust (AJW), Ted’s Gang (AJW) and the Cambridge NIHR Biomedical Research Centre.This is the author accepted manuscript. The final version is available from Nature Publishing Group via http://dx.doi.org/10.1038/nsmb.311

Free Energy Simulations of a GTPase: GTP and GDP Binding to Archaeal Initiation Factor 2

International audienceArchaeal initiation factor 2 (aIF2) is a protein involved in the initiation of protein biosynthesis. In its GTP-bound, "ON" conformation, aIF2 binds an initiator tRNA and carries it to the ribosome. In its GDP-bound, "OFF" conformation, it dissociates from tRNA. To understand the specific binding of GTP and GDP and its dependence on the ON or OFF conformational state of aIF2, molecular dynamics free energy simulations (MDFE) are a tool of choice. However, the validity of the computed free energies depends on the simulation model, including the force field and the boundary conditions, and on the extent of conformational sampling in the simulations. aIF2 and other GTPases present specific difficulties; in particular, the nucleotide ligand coordinates a divalent Mg(2+) ion, which can polarize the electronic distribution of its environment. Thus, a force field with an explicit treatment of electronic polarizability could be necessary, rather than a simpler, fixed charge force field. Here, we begin by comparing a fixed charge force field to quantum chemical calculations and experiment for Mg(2+):phosphate binding in solution, with the force field giving large errors. Next, we consider GTP and GDP bound to aIF2 and we compare two fixed charge force fields to the recent, polarizable, AMOEBA force field, extended here in a simple, approximate manner to include GTP. We focus on a quantity that approximates the free energy to change GTP into GDP. Despite the errors seen for Mg(2+):phosphate binding in solution, we observe a substantial cancellation of errors when we compare the free energy change in the protein to that in solution, or when we compare the protein ON and OFF states. Finally, we have used the fixed charge force field to perform MDFE simulations and alchemically transform GTP into GDP in the protein and in solution. With a total of about 200 ns of molecular dynamics, we obtain good convergence and a reasonable statistical uncertainty, comparable to the force field uncertainty, and somewhat lower than the predicted GTP/GDP binding free energy differences. The sign and magnitudes of the differences can thus be interpreted at a semiquantitative level, and are found to be consistent with the experimental binding preferences of ON- and OFF-aIF2