151 research outputs found

    Tryptophan-Accelerated Electron Flow Across a Protein−Protein Interface

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    We report a new metallolabeled blue copper protein, Re126W122Cu^I Pseudomonas aeruginosa azurin, which has three redox sites at well-defined distances in the protein fold: Re^I(CO)_3(4,7-dimethyl-1,10-phenanthroline) covalently bound at H126, a Cu center, and an indole side chain W122 situated between the Re and Cu sites (Re-W122(indole) = 13.1 Å, dmp-W122(indole) = 10.0 Å, Re-Cu = 25.6 Å). Near-UV excitation of the Re chromophore leads to prompt Cu^I oxidation (<50 ns), followed by slow back ET to regenerate Cu^I and ground-state Re^I with biexponential kinetics, 220 ns and 6 μs. From spectroscopic measurements of kinetics and relative ET yields at different concentrations, it is likely that the photoinduced ET reactions occur in protein dimers, (Re126W122CuI)2 and that the forward ET is accelerated by intermolecular electron hopping through the interfacial tryptophan: ^*Re//←W122←Cu^I, where // denotes a protein–protein interface. Solution mass spectrometry confirms a broad oligomer distribution with prevalent monomers and dimers, and the crystal structure of the Cu^(II) form shows two Re126W122Cu^(II) molecules oriented such that redox cofactors Re(dmp) and W122-indole on different protein molecules are located at the interface at much shorter intermolecular distances (Re-W122(indole) = 6.9 Å, dmp-W122(indole) = 3.5 Å, and Re-Cu = 14.0 Å) than within single protein folds. Whereas forward ET is accelerated by hopping through W122, BET is retarded by a space jump at the interface that lacks specific interactions or water molecules. These findings on interfacial electron hopping in (Re126W122Cu^I)^2 shed new light on optimal redox-unit placements required for functional long-range charge separation in protein complexes

    Evolutionary genetics of immunological supertypes reveals two faces of the Red Queen

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    Red Queen host-parasite co-evolution can drive adaptations of immune-genes by positive selection that erodes genetic variation (Red Queen Arms Race), or result in a balanced polymorphism (Red Queen Dynamics) and the long-term preservation of genetic variation (trans-species polymorphism). These two Red Queen processes are opposite extremes of the co-evolutionary spectrum. Here we show that both Red Queen processes can operate simultaneously, analyzing the Major Histocompatibility Complex (MHC) in guppies (Poecilia reticulata and P. obscura), and swamp guppies (Micropoecilia picta). Sub-functionalization of MHC alleles into “supertypes” explains how polymorphisms persist during rapid host-parasite co-evolution. Simulations show the maintenance of supertypes as balanced polymorphisms, consistent with Red Queen Dynamics, whereas alleles within supertypes are subject to positive selection in a Red Queen Arms Race. Building on the Divergent Allele Advantage hypothesis, we show that functional aspects of allelic diversity help to elucidate the evolution of polymorphic genes involved in Red Queen co-evolution

    Database-driven High-Throughput Calculations and Machine Learning Models for Materials Design

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    This paper reviews past and ongoing efforts in using high-throughput ab-inito calculations in combination with machine learning models for materials design. The primary focus is on bulk materials, i.e., materials with fixed, ordered, crystal structures, although the methods naturally extend into more complicated configurations. Efficient and robust computational methods, computational power, and reliable methods for automated database-driven high-throughput computation are combined to produce high-quality data sets. This data can be used to train machine learning models for predicting the stability of bulk materials and their properties. The underlying computational methods and the tools for automated calculations are discussed in some detail. Various machine learning models and, in particular, descriptors for general use in materials design are also covered.Comment: 19 pages, 2 figure

    TENDENCIES OF CLIMATIC EXTREMES OCCURRENCE IN DIFFERENT MORAVIAN REGIONS AND LANDSCAPE TYPES

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    Abstract MUŽÍKOVÁ, B., VLČEK, V., STŘEDA, T.: Tendencies of climatic extremes occurrence in diff erent Moravian regions and landscape types. Acta univ. agric. et silvic. Mendel. Brun., 2011, LIX, No. 5, pp. 169-178 In this study present frequency of several characteristic days as tropical, summer, arctic, frost and ice days and also length of heat waves was compared with modelled future occurrence of these climate extreme indices. Climate-diagrams were used for drought hazard assessment. The main objective of our research was to detect possible changes of frequency of the extreme events toward future. Data from four localities in the Czech Republic (Moravia) were chosen for the evaluation. Each locality represents diff erent climatic, landscape and settlement conditions. Localities are represented by the closest grid points. Future trend was modelled for scenario data (scenario A1B) by regional model ALADIN-Climate/CZ in the Czech Hydrometeorological Institute. The results showed obvious rising tendency of tropical and summer days frequency on all localities, especially in lowland regions. Very strong decreasing trend seemed to be in occurrence of arctic days, which might be very scarce in the future. Frost days and ice days should also decrease. Increase in number of days in heat wave was considerable. Climate-diagrams showed possible rising drought hazard for all localities towards future periods. characteristic days, climatic extremes, ALADIN Extreme climatic events can have serious impact on environment and society. Analyses of observed temperature in many regions of the world have already shown some important changes in the extremes occurrence. The extreme climatic events are mainly associated with precipitation and temperature. Global air temperature has increased by an average of 0.74 °C (IPCC 4th Assessment Report 2007) in last hundred years. Generally, the global daily minimum and maximum air temperature values (Tmin and Tmax) increase, though the minima increase three times faster The research of tendencies of several climatic extreme indices has been realized in many countries all over the world. A study of the longterm changes of various climatic extremes was made jointly by a number of European countries. It was found that the changes in maximum and minimum temperatures follow the corresponding welldocumented mean temperature changes. Minimum temperatures, however, have increased slightly more than maximum temperatures, although both have increased. As a result, the study confi rmed that the diurnal temperature range has mostly decreased during the present century in Northern and Central Europe. Frost has become less frequent Not only changes in average or minimum and maximum air temperature are suitable to study changes of climatic conditions. Characteristic days (tropical, summer, ice, frost and arctic days) are also very useful indices. A research focused on such temperature characteristics was also done in Canada. Vincent and Mekis (2006) studied trends and variations in severa

    Controlled reactive HiPIMS – effective technique for lowtemperature deposition of VO2-based multilayer coatings for smart window applications

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    Studentská vědecká konference je pořádána s podporou prostředků na specifický vysokoškolský výzkum SVK1-2018-024.Vanadium dioxide (VO2) is a technologically important thin film material of a high current world wide interest due to its reversible first-order thermochromic transition relatively near room temperature (approximately 68°C). Magnetron sputtering is probably the most important preparation technique of VO2 films, and numerous deposition pathways have been reported in recent years. The research in this area is focused on (at least) the following three challenges. First, doping of VO2 by other metals in order to decrease the transition temperature (Ttr) from 68 °C (bulk materials) or e.g. 50 °C (thin films) to the room temperature. Second, decreasing the deposition temperature (Tdep) of crystalline VO2 at least below 300 °C, ideally without any substrate bias and without any crystalline interlayer, in order (i) to facilitate the large-scale production by reducing the energy consumption and minimizing problems with temperature uniformity over large substrate surfaces, (ii) to limit the diffusion of harmful elements from substrates such as soda-lime glass and (iii) to allow deposition on temperaturesensitive plastic substrates. Third, improving the luminous transmittance (Tlum) and the modulation of the solar transmittance (Tsol) of the coatings by antireflection (AR) layers. (J. Houška et al. (2017)
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