Deuterium isotope effect on the intramolecular electron transfer in Pseudomonas aeruginosa azurin

Intramolecular electron transfer in azurin in water and deuterium oxide has been studied over a broad temperature range. The kinetic deuterium isotope effect, kH/kD, is smaller than unity (0.7 at 298 K), primarily caused by the different activation entropies in water (���56.5 J K���1 mol���1) and in deuterium oxide (���35.7 J K���1 mol���1). This difference suggests a role for distinct protein solvation in the two media, which is supported by the results of voltammetric measurements: the reduction potential (E0���) of Cu2+/+ at 298 K is 10 mV more positive in D2O than in H2O. The temperature dependence of E0��� is also different, yielding entropy changes of ���57 J K���1 mol���1 in water and ���84 J K���1 mol���1 in deuterium oxide. The driving force difference of 10 mV is in keeping with the kinetic isotope effect, but the contribution to ��S��� from the temperature dependence of E0��� is positive rather than negative. Isotope effects are, however, also inherent in the nuclear reorganization Gibbs free energy and in the tunneling factor for the electron transfer process. A slightly larger thermal protein expansion in H2O than in D2O (0.001 nm K���1) is sufficient both to account for the activation entropy difference and to compensate for the different temperature dependencies of E0���. Thus, differences in driving force and thermal expansion appear as the most straightforward rationale for the observed isotope effect.

The Responses of Cytochrome Redox State and Energy Metabolism to Dehydration Support a Role for Cytoplasmic Viscosity in Desiccation Tolerance1

To characterize the depression of metabolism in anhydrobiotes, the redox state of cytochromes and energy metabolism were studied during dehydration of soaked cowpea (Vigna unguiculata) cotyledons and pollens of Typha latifolia and Impatiens glandulifera. Between water contents (WC) of 1.0 and 0.6 g H2O/g dry weight (g/g), viscosity as measured by electron spin resonance spectroscopy increased from 0.15 to 0.27 poise. This initial water loss was accompanied by a 50% decrease in respiration rates, whereas the adenylate energy charge remained constant at 0.8, and cytochrome c oxidase (COX) remained fully oxidized. From WC of 0.6 to 0.2 g/g, viscosity increased exponentially. The adenylate energy charge declined to 0.4 in seeds and 0.2 in pollen, whereas COX became progressively reduced. At WC of less than 0.2 g/g, COX remained fully reduced, whereas respiration ceased. When dried under N2, COX remained 63% reduced in cotyledons until WC was 0.7 g/g and was fully reduced at 0.2 g/g. During drying under pure O2, the pattern of COX reduction was similar to that of air-dried tissues, although the maximum reduction was 70% in dried tissues. Thus, at WC of less than 0.6 g/g, the reduction of COX probably originates from a decreased O2 availability as a result of the increased viscosity and impeded diffusion. We suggest that viscosity is a valuable parameter to characterize the relation between desiccation and decrease in metabolism. The implications for desiccation tolerance are discussed.

Recombinational repair of gaps in DNA is asymmetric in Ustilago maydis and can be explained by a migrating D-loop model.

Recombinational repair of double-stranded DNA gaps was investigated in Ustilago maydis. The experimental system was designed for analysis of repair of an autonomously replicating plasmid containing a cloned gene disabled by an internal deletion. It was discovered that crossing over rarely accompanied gap repair. The strong bias against crossing over was observed in three different genes regardless of gap size. These results indicate that gap repair in U. maydis is unlikely to proceed by the mechanism envisioned in the double-stranded break repair model of recombination, which was developed to account for recombination in Saccharomyces cerevisiae. Experiments aimed at exploring processing of DNA ends were performed to gain understanding of the mechanism responsible for the observed bias. A heterologous insert placed within a gap in the coding sequence of two different marker genes strongly inhibited repair if the DNA was cleaved at the promoter-proximal junction joining the insert and coding sequence but had little effect on repair if the DNA was cleaved at the promoter-distal junction. Gene conversion of plasmid restriction fragment length polymorphism markers engineered in sequences flanking both sides of a gap accompanied repair but was directionally biased. These results are interpreted to mean that the DNA ends flanking a gap are subject to different types of processing. A model featuring a single migrating D-loop is proposed to explain the bias in gap repair outcome based on the observed asymmetry in processing the DNA ends.

First Order Phase Transition in a 3D disordered system

We present a detailed numerical study on the effects of adding quenched impurities to a three dimensional system which in the pure case undergoes a strong first order phase transition (specifically, the ferromagnetic/paramagnetic transition of the site-diluted four states Potts model). We can state that the transition remains first-order in the presence of quenched disorder (a small amount of it) but it turns out to be second order as more impurities are added. A tricritical point, which is studied by means of Finite-Size Scaling, separates the first-order and second-order parts of the critical line. The results were made possible by a new definition of the disorder average that avoids the diverging-variance probability distributions that arise using the standard methodology. We also made use of a recently proposed microcanonical Monte Carlo method in which entropy, instead of free energy, is the basic quantity.

Optical control of the spin state of two Mn atoms in a quantum dot

We report on the optical spectroscopy of the spin of two magnetic atoms (Mn) embedded in an individual quantum dot interacting with a single electron, a single exciton, or a single trion. As a result of their interaction to a common entity, the Mn spins become correlated. The dynamics of this process is probed by time-resolved spectroscopy, which permits us to determine an optical orientation time in the range of a few tens of nanoseconds. In addition, we show that the energy of the collective spin states of the two Mn atoms can be tuned through the optical Stark effect induced by a resonant laser field.

Nitrogen regulation of protein���protein interactions and transcript levels of GlnK PII regulator and AmtB ammonium transporter homologs in Archaea

Gene homologs of GlnK PII regulators and AmtB-type ammonium transporters are often paired on prokaryotic genomes, suggesting these proteins share an ancient functional relationship. Here, we demonstrate for the first time in Archaea that GlnK associates with AmtB in membrane fractions after ammonium shock, thus, providing a further insight into GlnK-AmtB as an ancient nitrogen sensor pair. For this work, Haloferax mediterranei was advanced for study through the generation of a pyrE2-based counterselection system that was used for targeted gene deletion and expression of Flag-tagged proteins from their native promoters. AmtB1-Flag was detected in membrane fractions of cells grown on nitrate and was found to coimmunoprecipitate with GlnK after ammonium shock. Thus, in analogy to bacteria, the archaeal GlnK PII may block the AmtB1 ammonium transporter under nitrogen-rich conditions. In addition to this regulated protein���protein interaction, the archaeal amtB-glnK gene pairs were found to be highly regulated by nitrogen availability with transcript levels high under conditions of nitrogen limitation and low during nitrogen excess. While transcript levels of glnK-amtB are similarly regulated by nitrogen availability in bacteria, transcriptional regulators of the bacterial glnK promoter including activation by the two-component signal transduction proteins NtrC (GlnG, NRI) and NtrB (GlnL, NRII) and sigma factor ��N (��54) are not conserved in archaea suggesting a novel mechanism of transcriptional control.

Simulation of the secondary electrons energy deposition produced by proton beams in PMMA: influence of the target electronic excitation description

We have studied the radial dependence of the energy deposition of the secondary electron generated by swift proton beams incident with energies T = 50 keV���5 MeV on poly(methylmethacrylate) (PMMA). Two different approaches have been used to model the electronic excitation spectrum of PMMA through its energy loss function (ELF), namely the extended-Drude ELF and the Mermin ELF. The singly differential cross section and the total cross section for ionization, as well as the average energy of the generated secondary electrons, show sizeable differences at T ��� 0.1 MeV when evaluated with these two ELF models. In order to know the radial distribution around the proton track of the energy deposited by the cascade of secondary electrons, a simulation has been performed that follows the motion of the electrons through the target taking into account both the inelastic interactions (via electronic ionizations and excitations as well as electron-phonon and electron trapping by polaron creation) and the elastic interactions. The radial distribution of the energy deposited by the secondary electrons around the proton track shows notable differences between the simulations performed with the extended-Drude ELF or the Mermin ELF, being the former more spread out (and, therefore, less peaked) than the latter. The highest intensity and sharpness of the deposited energy distributions takes place for proton beams incident with T ~ 0.1���1 MeV. We have also studied the influence in the radial distribution of deposited energy of using a full energy distribution of secondary electrons generated by proton impact or using a single value (namely, the average value of the distribution); our results show that differences between both simulations become important for proton energies larger than ~0.1 MeV. The results presented in this work have potential applications in materials science, as well as hadron therapy (due to the use of PMMA as a tissue phantom) in order to properly consider the generation of electrons by proton beams and their subsequent transport and energy deposition through the target in nanometric scales.

Magnetic Edge Anisotropy in Graphenelike Honeycomb Crystals

The independent predictions of edge ferromagnetism and the quantum spin Hall phase in graphene have inspired the quest of other two-dimensional honeycomb systems, such as silicene, germanene, stanene, iridates, and organometallic lattices, as well as artificial superlattices, all of them with electronic properties analogous to those of graphene, but a larger spin-orbit coupling. Here, we study the interplay of ferromagnetic order and spin-orbit interactions at the zigzag edges of these graphenelike systems. We find an in-plane magnetic anisotropy that opens a gap in the otherwise conducting edge channels that should result in large changes of electronic properties upon rotation of the magnetization.

Direitos sociais na Constitui����o: uma an��lise da constitucionaliza����o dos direitos sociais em Portugal, 1975-76

Embora todas as constitui����es incluam direitos, e muitas delas incluam direitos sociais, a verdade �� que algumas s��o mais generosas do que outras a este respeito. Mas nenhuma se aproxima da Constitui����o da Rep��blica Portuguesa de 1976 no que toca �� extens��o e detalhe do seu cat��logo de direitos sociais, econ��micos e culturais. As principais teorias sobre as origens de institui����es geraram hip��teses explicativas da constitucionaliza����o desta segunda gera����o de direitos. Sucede, por��m, que estas hip��teses n��o conseguem explicar de forma totalmente convincente o processo de constitucionaliza����o dos direitos sociais. Isto �� ainda mais verdade em casos como o do nosso pa��s, cujo car��cter discrepante os tornam ainda mais dif��ceis de explicar. Neste artigo, estas teorias e respectivas hip��teses ser��o testadas por rela����o ao caso portugu��s o qual ser��, sempre que se revelar necess��rio, comparado com o espanhol. Visamos alcan��ar dois objectivos com este exerc��cio. Por um lado, pretendemos identificar as limita����es das explica����es dominantes, incluindo as teorias e hip��teses sobre os mecanismos causais respons��veis pela inclus��o de direitos sociais nas constitui����es. Por outro lado, o nosso prop��sito �� o de conceber explica����es alternativas sempre que as existentes se revelem inadequadas ou insuficientes.

The expensive energy revolution in Germany. The implementation of the Energiewende is behind schedule. OSW Commentary No. 77, 2012-05-10

One year after the events of Fukushima the implementation of the new German energy strategy adopted in the summer of 2011 is being verified. Business circles, experts and publicists are sounding the alarm. The tempo at which the German economy is being rearranged in order that it uses renewable energy sources is so that it has turned out to be an extremely difficult and expensive task. The implementation of the key guidelines of the new strategy, such as the development of the transmission networks and the construction of new conventional power plants, is meeting increasing resistance in the form of economic and legal difficulties. The development of the green technologies sector is also posing problems. The solar energy industry, for example, is excessively subsidised, whereas the subsidies for the construction of maritime wind farms are too low. At present, only those guidelines of the strategy which are evaluated as economically feasible by investors or which receive adequate financial support from the state have a chance of being carried through. The strategy may also turn out to be unsuccessful due to the lack of a comprehensive coordination of its implementation and the financial burden its introduction entails for both the public and the economy. In the immediate future, the German government will make efforts not only to revise its internal regulations in order to enable the realisation of the energy transformation; it is also likely to undertake a number of measures at the EU forum which will facilitate this realisation. One should expect that the German government will actively support the financing of both the development of the energy networks in EU member states and the development of renewable energy sources in the energy sector.

Necessary desirability: The inherent contradiction in the European system. EuropEos Commentary No. 11, 9 June 2011

In all political systems there is a gap between the rhetoric of electoral programmes and the practical work of institutions, argues author Riccardo Perissich, but the ���vision thing��� is often a necessary prerequisite to reaching difficult decisions. When it comes to European institutions, which include the member states acting collectively, the desirable vision ��� the goal of European unity ��� has always been there and is still very much alive. Also, the existence of a broadly defined political goal has often facilitated agreements that were in fact purely necessary. However, because we lack a pan-European constituency to debate it, the narrative about this goal has been translated into different languages and is all but common. In fact, we have never seriously tried to unify it. Indeed, Europeans stopped debating what is desirable a long time ago: they simply react to events.

Shale gas in Europe: much ado about little? Egmont Paper No. 64, March 2014

Introduction. Shale gas is an unconventional form of gas1 because its extraction is more difficult or less economical than that of conventional natural gas. It has become an important item of energy policy during the last years since new processes have allowed its extraction. In the medium term, shale gas should foster a reinforcement of the gas part in the world���s energy mix. In 2011, the IEA released an influential report entitled ���Are we entering a golden age of gas?��� This report suggests that shale gas could help substantially boost global gas use.2 It also warns at the same time that this success could bring into question the international goal of limiting the long-term increase in the global temperature to 2�� C above pre-industrial levels. In the world economy, the impact of shale gas is increasing rapidly (especially in the USA, albeit apparently not as significantly as expected3). In the EU, its perspectives remain uncertain, for many reasons. Estimates are not reliable. Shale gas exploitation remains a controversial issue due to geology, lack of infrastructure and also fears for the environment and public health. The EU institutions seem to have a favorable attitude towards shale gas development while the Member States��� attitude seems to vary from enthusiasm to hesitation or opposition. Public opinion on the issue appears quite divided everywhere. This brief paper will examine various estimations of potential resources in the EU (�� 1), the potential costs and benefits (�� 2), the initiatives taken by the EU institutions (�� 3) and the national authorities (�� 4), and finally the emerging EU framework (�� 5). The conclusion is, rather surprisingly, that whatever happens on this front, this will not modify the present structural challenges of the EU in the domains of climate and energy.4

The Path to European Integration: A Historical Institutionalist Perspective, CES Germany & Europe Working Papers, No. 05.2, 25 October 1994

Many European and American observers of the EC have criticized "intergovemmentalist" ac�� counts for exaggerating the extent of member state control over the process of European integra�� tion. This essay seeks to ground these criticisms in a "historical institutionalist" account that stresses the need to study European integration as a political process which unfolds over time. Such a perspective highlights the limits of member-state control over long-term institutional de�� velopment, due to preoccupation with shorHerm concerns, the ubiquity of unintended conse�� quences, and processes that "lock in" past decusions and make reassertions of member-state control difficult. Brief examination of the evolution of social policy in the EC suggests the limita�� tions of treating the EC as an international regime facilitating collective action among essentially sovereign states. It is ore useful to view integration as a "path-dependent" process that has pro�� duced a fragmented but still discernible "multitiered" European polity.

Verhalten von Ladungsverst��rkern bei verschiedenen Eingangsimpulsformen und -zeiten

In dieser Arbeit wird das Verhalten eines Ladungsverst��rkers bei verschiedenen Eingangsimpulsformen und -zeiten untersucht. Als erstes wird der derzeitige Stand der Technik dargelegt und die Funktionsweise eines Ladungsverst��rkers erl��utert. Um die Messungen am Ladungsverst��rker durchzuf��hren, wurde ein Messprogramm in LabView geschrieben und das verwendete Messsystem auf seine Tauglichkeit untersucht. Dazu wurde unter anderem eine Software entwickelt, die einen Ladungsverst��rker simuliert. Nach einer kurzen Betrachtung m��glicher Fehlereinfl��sse, die bei der Digitalisierung von Messsignalen auftreten k��nnen, wurde eine Messunsicherheitsbetrachtung nach dem ���Guide to the Expression of Uncertainty in Measurement��� (GUM) durchgef��hrt. Um den gemessenen ��bertragungskoeffizienten des Ladungsverst��rkers mit dem herk��mmlichen Kalibrierverfahren (sinusf��rmiges Eingangssignal) vergleichbar zu machen, wurde eine Fourier-Analyse der Messsignale angewendet. F��r den Frequenzbereich unterhalb von 20 kHz ergibt sich eine gute ��bereinstimmung des ��bertragungsverhaltens des Ladungsverst��rkers mit dem herk��mmlichen Kalibierverfahren bei Anregungen mit verschiedenen impulsf��rmigen Eingangssignalen. Oberhalb von 20 kHz weichen die Ergebnisse der zwei Messverfahren voneinander ab, da die maximale Signalanstiegsrate des Ladungsverst��rkers ��berschritten wird.

The spectrographic determination of cesium in plutonium metal /

A spectrographic-photometric procedure has been developed for the determination of cesium in plutonium metal.