Dual tRNA mimicry in the Cricket Paralysis Virus IRES uncovers an unexpected similarity with the Hepatitis C Virus IRES

Co-opting the cellular machinery for protein production is a compulsory requirement for viruses. The Cricket Paralysis Virus employs an Internal Ribosomal Entry Site (CrPV-IRES) to express its structural genes in the late stage of infection. Ribosome hijacking is achieved by a sophisticated use of molecular mimicry to tRNA and mRNA, employed to manipulate intrinsically dynamic components of the ribosome. Binding and translocation through the ribosome is required for this IRES to initiate translation. We report two structures, solved by single particle electron cryo-microscopy (cryoEM), of a double translocated CrPV-IRES with aminoacyl-tRNA in the peptidyl site (P site) of the ribosome. CrPV-IRES adopts a previously unseen conformation, mimicking the acceptor stem of a canonical E site tRNA. The structures suggest a mechanism for the positioning of the first aminoacyl-tRNA shared with the distantly related Hepatitis C Virus IRES

Terahertz and infrared spectroscopic evidence of phonon-paramagnon coupling in hexagonal piezomagnetic YMnO3

Terahertz and far-infrared electric and magnetic responses of hexagonal piezomagnetic YMnO3 single crystals are investigated. Antiferromagnetic resonance is observed in the spectra of magnetic permeability mu_a [H(omega) oriented within the hexagonal plane] below the Neel temperature T_N. This excitation softens from 41 to 32 cm-1 on heating and finally disappears above T_N. An additional weak and heavily-damped excitation is seen in the spectra of complex dielectric permittivity epsilon_c within the same frequency range. This excitation contributes to the dielectric spectra in both antiferromagnetic and paramagnetic phases. Its oscillator strength significantly increases on heating towards room temperature thus providing evidence of piezomagnetic or higher-order couplings to polar phonons. Other heavily-damped dielectric excitations are detected near 100 cm-1 in the paramagnetic phase in both epsilon_c and epsilon_a spectra and they exhibit similar temperature behavior. These excitations appearing in the frequency range of magnon branches well below polar phonons could remind electromagnons; however, their temperature dependence is quite different. We have used density functional theory for calculating phonon dispersion branches in the whole Brillouin zone. A detailed analysis of these results and of previously published magnon dispersion branches brought us to the conclusion that the observed absorption bands stem from phonon-phonon and phonon- paramagnon differential absorption processes. The latter is enabled by a strong short-range in-plane spin correlations in the paramagnetic phase.Comment: subm. to PR

Defects as a reason of continuity of normal-incommensurate phase transitions

Almost all normal-incommensurate phase transitions observed experimentally are continuous. We show that there is not any theoretical reason for this general behaviour in perfect crystals. A normal-incommensurate phase transition that is not too far from the mean-field tricritical point should be discontinuous and it is highly improbable that so far reported normal-incommensurate phase transitions lie very far from this point. To understand this behaviour we study influence of defects on a hypothetical first-order normal-incommensurate phase transition in a pure material. We have found that this influence is strikingly different from that on other kinds of first-order phase transitions. The change of the discontinuity of the order parameter at the transition is negative and formally diverges within our approximate theory. At the same time the diminishing of the phase transition temperature remains finite. We interpret these results as an indication that at least some of the observed seemingly second-order normal-incommensurate transitions would be first-order transitions in defectless crystals.Comment: 17 pages, 1 figur

Very high frequency gravitational wave background in the universe

Astrophysical sources of high frequency gravitational radiation are considered in association with a new interest to very sensitive HFGW receivers required for the laboratory GW Hertz experiment. A special attention is paid to the phenomenon of primordial black holes evaporation. They act like black body to all kinds of radiation, including gravitons, and, therefore, emit an equilibrium spectrum of gravitons during its evaporation. Limit on the density of high frequency gravitons in the Universe is obtained, and possibilities of their detection are briefly discussed.Comment: 14 page

Электропривод транспортного средства сельскохозяйственного назначения

Abstract. The authors showed the relevance of creating agricultural machines using an electric drive. (Research purpose) The research objective is to develop an experimental prototype vehicle using an electrical schematic diagram of charge and electric drive control. (Materials and methods) The VAZ 111 Oka car was chosen as an experimental vehicle model with an electric drive, since it has a light weight of 645 kilograms, a simple design and a low cost. Mechanical characteristics of the electric motor were calculated and a frequency converter was chosen to control the electric drive.  Laboratory bench tests were conducted. (Results and discussion)The authors   installed storage batteries to power the electric drive, developed an electrical circuit schematics getting charged from a 220 volt alternating voltage network, and received graphs for the discharge of a 40-storage-battery power supply. (Conclusions) An electrical schematic diagram of charge and electric drive control was developed and implemented on an experimental vehicle model. It was determined that at the electric motor continuous operation with the load current of 1 ampere, the batteries get discharged within 104 minutes;  with the current  load of 2 amperes, they get  discharged within 83 minutes; with 3 amperes – within 65 minutes, and with 5 amperes – within 50 minutes, which is enough to drive around the farm. The authors graphically depicted the dependence of the available capacity level on the voltage, as well as the batteries’ discharge on the time at various load currents. The authors carried out two experimental studies on storage batteries’ charging from alternating voltage with the current of 2 and 3 amperes: in the first case, the charging time was 350 minutes, in the second – 310 minutes. It was found out that when using the developed scheme, the batteries are charged evenly.Показали актуальность создания сельскохозяйственных машин с применением электропривода. (Цель исследования) Разработать экспериментальный образец транспортного средства с использованием электрической принципиальной схемы управления зарядом и электроприводом. (Материалы и методы) В качестве экспериментального образца транспортного средства с электроприводом выбрали автомобиль «ВАЗ 111 Ока», так как он имеет небольшую массу – 645 килограммов, простую конструкцию и невысокую стоимость. Рассчитали механические характеристики электродвигателя и выбрали частотный преобразователь для управления электроприводом. Провели испытания на лабораторном стенде. (Результаты и обсуждение) Установили аккумуляторные батареи для питания электропривода и разработали электрическую принципиальную систему заряда от стандартной сети переменного напряжения 220 вольт. Получили графики разряда источника питания, состоящего из 40 аккумуляторных батарей. (Выводы) Разработали электрическую принципиальную схему управления зарядом и электроприводом и реализовали ее на экспериментальном образце транспортного средства. Определили, что с током нагрузки 1 ампер аккумуляторные батареи разряжаются в течение 104 минут, с током 2 ампера – 83 минуты, 3 ампера – 65 минут, а с током 5 ампер – 50 минут, при постоянной работе электродвигателя, что достаточно для езды по ферме. Графически изобразили зависимости уровня доступной емкости от напряжения, а также разряда аккумуляторных батарей от времени при различных токах нагрузки. Провели два экспериментальных исследования по заряду аккумуляторных батарей от переменного напряжения с током 2 и 3 ампера: в первом случае время зарядки составило 350 минут, во втором – 310 минут. Выяснили, что при использовании разработанной схемы аккумуляторные батареи заряжаются равномерно

On the choice of heavy baryon currents in the relativistic three-quark model

We test the sensitivity of bottom baryon observables with regard to the choice of the interpolating three-quark currents within the relativistic three-quark model. We have found that the semileptonic decay rates are clearly affected by the choice of currents, whereas the asymmetry parameters show only a very weak dependence on the choice of current.Comment: revtex, 9 page

The Role of Regulated mRNA Stability in Establishing Bicoid Morphogen Gradient in Drosophila Embryonic Development

The Bicoid morphogen is amongst the earliest triggers of differential spatial pattern of gene expression and subsequent cell fate determination in the embryonic development of Drosophila. This maternally deposited morphogen is thought to diffuse in the embryo, establishing a concentration gradient which is sensed by downstream genes. In most model based analyses of this process, the translation of the bicoid mRNA is thought to take place at a fixed rate from the anterior pole of the embryo and a supply of the resulting protein at a constant rate is assumed. Is this process of morphogen generation a passive one as assumed in the modelling literature so far, or would available data support an alternate hypothesis that the stability of the mRNA is regulated by active processes? We introduce a model in which the stability of the maternal mRNA is regulated by being held constant for a length of time, followed by rapid degradation. With this more realistic model of the source, we have analysed three computational models of spatial morphogen propagation along the anterior-posterior axis: (a) passive diffusion modelled as a deterministic differential equation, (b) diffusion enhanced by a cytoplasmic flow term; and (c) diffusion modelled by stochastic simulation of the corresponding chemical reactions. Parameter estimation on these models by matching to publicly available data on spatio-temporal Bicoid profiles suggests strong support for regulated stability over either a constant supply rate or one where the maternal mRNA is permitted to degrade in a passive manner

Gene expression changes and community turnover differentially shape the global ocean metatranscriptome

Ocean microbial communities strongly influence the biogeochemistry, food webs, and climate of our planet. Despite recent advances in understanding their taxonomic and genomic compositions, little is known about how their transcriptomes vary globally. Here, we present a dataset of 187 metatranscriptomes and 370 metagenomes from 126 globally distributed sampling stations and establish a resource of 47 million genes to study community-level transcriptomes across depth layers from pole-to-pole. We examine gene expression changes and community turnover as the underlying mechanisms shaping community transcriptomes along these axes of environmental variation and show how their individual contributions differ for multiple biogeochemically relevant processes. Furthermore, we find the relative contribution of gene expression changes to be significantly lower in polar than in non-polar waters and hypothesize that in polar regions, alterations in community activity in response to ocean warming will be driven more strongly by changes in organismal composition than by gene regulatory mechanisms