An atomic model of the outer layer of the bluetongue virus core derived from X-ray crystallography and electron cryomicroscopy

BACKGROUND: Bluetongue virus (BTV), which belongs to the Reoviridae family and orbivirus genus, is a non-enveloped, icosahedral, double-stranded RNA virus. Several protein layers enclose its genome; upon cell entry the outer layer is stripped away leaving a core, the surface of which is composed of VP7. The structure of the trimeric VP7 molecule has previously been determined using X-ray crystallography. The articulated VP7 subunit consists of two domains, one which is largely alpha-helical and the other, smaller domain, is a beta barrel with jelly-roll topology. The relative orientations of these two domains vary in different crystal forms. The structure of VP7 and the organizations of 780 subunits of this molecule in the core of virus is central to the assembly and function of BTV. RESULTS: A 23 A resolution map of the core, determined using electron cryomicroscopy (cryoEM) data, reveals that the 260 trimers of VP7 are organized on a rather precise T = 13 laevo icosahedral lattice, in accordance with the theory of quasi-equivalence. The VP7 layer occupies a shell that is between 260 A and 345 A from the centre of the core. Below this radius (230-260 A) lies the T = 1 layer of 120 molecules of VP3. By fitting the X-ray structure of an individual VP7 trimer onto the cryoEM BTV core structure, we have generated an atomic model of the VP7 layer of BTV. This demonstrates that one of the molecular structures seen in crystals of the isolated VP7 corresponds to the in vivo conformation of the molecule in the core. CONCLUSIONS: The beta-barrel domains of VP7 are external to the core and interact with protein in the outer layer of the mature virion. The lower, alpha-helical domains of VP7 interact with VP3 molecules which form the inner layer of the BTV core. Adjacent VP7 trimer-trimer interactions in the T = 13 layer are mediated principally through well-defined regions in the broader lower domains, to form a structure that conforms well with that expected from the theory of quasi-equivalence with no significant conformational changes within the individual trimers. The VP3 layer determines the particle size and forms a rather smooth surface upon which the two-dimensional lattice of VP7 trimers is laid down.     

Linear signal distortion compensation using harmonic decomposition

Compensating for linear distortions of a signal under uniform sampling using Fourier series is considered.     

Initiation of combustion of titanium plates in an air stream by pulsed radiation

We have experimentally investigated the effect of the velocity of an air stream and the static pressure in the stream in the subsonic, near sonic, and supersonic flow regimes on the process of initiation of self-sustaining combustion of plates made from titanium alloy OT4-1V by pulsed laser radiation. We have established the existence of an upper limit for the flow velocity for initiation of combustion. We have shown that reduction of the static pressure below atmospheric leads to a sharp reduction of the range of flow velocities for which self sustaining combustion of the plates is initiated; and for p<0.6·10⁵ Pa, combustion does not develop over the entire range of M numbers from 0 to 2.5.Central Institute of Aerodynamics, 3 Zhukovskii 140160. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 2, pp. 46–51, March–April, 1994.     

Use of subjective and nonsubjective methodologies to evaluate lens radiation damage in exposed populations--an overview

The general epidemiological acceptability of prevalence, or incidence, for assessing risk of radiation cataract development has dictated an almost exclusive dependence on cataract onset as a measure of cataractogenicity for given doses of radiation. The advent of instrumentation capable of acquiring images amenable to quantitative analyses offers the possibility of exploiting "relative opacification" as an added, if not exclusive, parameter. This development is particularly important in efforts to assess populations such as that in the Altai, which are temporally far removed from their exposure and among whom there exists a large subset with extant cataracts. The new technologies, Scheimpflug and retroillumination imaging, combined with the application of the appropriate analytical algorithms can not only provide quantitative and nonsubjective assessment of lens transparency, but also serve as a means to immortalize the state of the pathology at the time of acquisition. Highly relevant to the assessment of an aging exposed population is the use of lens epithelial fragments as potential dosimeters. The material is routinely available as a result of cataract extraction procedures and is amenable to the application of a modified micronucleus (MN) assay. The MN assay in the lens has tremendous advantages over its use in other tissues for a number of reasons, not least of which is that lens MNs are extremely long-lived. Given the relative ease of application and its potential as a radiation bioindicator, the lens MN assay should be considered in any follow-up of populations exposed to ionizing radiation.     

Design of interval observers for uncertain dynamical systems

Interval state observers provide an estimate on the set of admissible values of the state vector at each instant of time. Ideally, the size of the evaluated set is proportional to the model uncertainty, thus interval observers generate the state estimates with estimation error bounds, similarly to Kalman filters, but in the deterministic framework. Main tools and techniques for design of interval observers are reviewed in this tutorial for continuous-time, discrete-time and time-delayed systems.     

Control problems in contingency during flight of a space vehicle with low thrust engine

An approximate method of online analysis of contingency during the flight of a space vehicle with low thrust engine and nuclear power unit to asteroids is proposed. The properties of dependence of the vehicle mass near the target on the flight characteristics and parameters of the space vehicle are used. Examples of the choice of a new variant of the expedition to several asteroids of the Main belt in the case of a contingent change in the power of the energy unit are given.     

The morphological mechanism of the development of myosatellitocytes from the structural elements of the muscle fiber during increased functional activity of the skeletal muscles

Under increased muscular activity in some muscular fibers disintegration areas of myofibrillar apparatus has been revealed. Migration of myonuclei into these microregions starts the mechanism of their segregation due to plasmolemma produced from the reticulum sarcoplasmaticum and triad systems surface. After plasmolemma production in "sarcocytes" intensive development and differentiation of organellae occur. As a result of differentiation "sarcocytes" transform in to myosatellitocytes of type-2 and migrate under lamina externa muscular fibers. So, a hypothesis about formation of myogenic tissue's cellular phase from the myosymplastic one has been confirmed.     

Increasing the Resistance of Automobile Sheet to Atmospheric Corrosion by Optimizing its Chemical Composition and the Parameters of the Manufacturing Process

A method involving alternating immersion in a 3.5% NaCl solution has been developed for corrosion tests of automobile sheet. Results obtained from 30 cycles of tests (10 + 50 min) of specimens of steels 08Yu, 08ps, 08YuP, 08YuDP, 08GSYuT, and IF established the dependence of the steel's unit weight gain from corrosion products on its combined content of carbon and silicon: steels with a lower content of these elements show a smaller gain in weight, i.e., they exhibit greater corrosion resistance. Steel alloyed with copper (0.23–0.34%) and phosphorus (0.06–0.08%) – the production of which has been mastered by the company Severstal' — has the highest resistance to corrosion. Use of the method makes it possible to rank grades of automobile sheet in one of three corrosion-resistance classifications in relation to their chemical composition and the parameters of the production process. __________ Translated from Metallurg, No. 8, pp. 46–52, August, 2005.