The eukaryotic nucleosome, the basic unit of chromatin, is thermodynamically stable and plays critical roles in the cell, including the maintenance of DNA topology and regulation of gene expression. At its C2 axis of symmetry, the nucleosome exhibits a domain that can coordinate divalent metal ions. This article discusses the roles of the metal‐binding domain in the nucleosome structure, function, and evolution.

RNA can catalyse chemical reactions through its ability to fold into complex three‐dimensional structures and to specifically bind small molecules and divalent metal ions. The 2′‐hydroxyl groups of the ribose moieties contribute to this exceptional reactivity of RNA, compared to DNA. RNA is not only able to catalyse phosphate ester transfer reactions in ribonucleic acids, but can also show aminoacyl esterase activity, and is probably able to promote peptide bond formation. Bearing its potential for functioning both as (...) a genome and as a gene product, RNA is suitable for in vitro evolution experiments enabling the selection of molecules with new properties. The growing repertoire of RNA catalysed reactions will establish RNA as a primordial molecule in the evolution of life. (shrink)

Metal ions may play an essential role in chromatin organization and, thus, be main actors in the gene expression drama. A model is proposed here for the interaction of DNA‐binding transcriptional regulatory proteins with histone H3 via coordinated metal ions and discussed in relation to the conversion of nucleosomal ‘closed’ to ‘open’ states.

Metallothioneins (MTs) are ubiquitous proteins with the capacity to bind heavy metal ions (mainly Cd, Zn or Cu), and they have been found in animals, plants, eukaryotic and prokaryotic micro‐organisms. We have carried out a comparative analysis of ciliate MTs (Tetrahymena species) to well‐known MTs from other organisms, discussing their exclusive features, such as the presence of aromatic amino acid residues and almost exclusive cysteine clusters (CCC) present in cadmium‐binding metallothioneins (CdMTs), higher heavy metal‐MT stoichiometry values, and (...) a strictly conserved modular–submodular structure. Based on this last feature and an extensive gene duplication, we propose a possible model for the evolutionary history of T. thermophila MTs. We also suggest possible functions for these MTs from consideration of their differential gene expressions and discuss the potential use of these proteins and/or their gene promoters for designing molecular or whole‐cell biosensors for a fast detection of heavy metals in diverse polluted ecosystems. (shrink)

The identification of additional subunits of the cGMP-gated cation channel suggests exciting questions about their regulatory roles and about structure/functional relationships. How do the different subunits interact? How is the complex assembled into the plasma membrane? Divalent cations have been implicated in the regulation of adaptation. One often overlooked cation is magnesium. Could this ion play a role in phototransduction?

Protein redox reactions are one of the most basic and important biochemical actions. As amino acids are weak redox mediators, most protein redox functions are undertaken by protein cofactors, which include organic ligands and transition metal ions. Since both kinds of redox cofactors were available in the pre‐protein RNA world, it is challenging to explore which one was more involved in redox processes of primitive proteins? In this paper, using an examination of the redox cofactor usage of putative (...) ancient proteins, we infer that organic ligands participated more frequently than transition metals in redox reactions of primitive proteins, at least as protein cofactors. This is further supported by the relative abundance of amino acids in the primordial world. Supplementary material for this article can be found on the BioEssays website. BioEssays 30:766–771, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

Immobilized Metal‐ion Affinity Chromatography, IMAC, has been gaining in popularity as the purification technique of choice for proteins and peptides. IMAC of proteins on transition metals (Co, Ni, Cu, Zn) can be rationalized in terms of the coordination of histidine residues. Brief accounts of the principles of IMAC, its anticipated development and plausible applications are presented. Metal Ion Transfer, MIT, may offer an efficient means to deplete a metal ion from a metalloprotein or, conversely, to charge its (...) apo form with a metal. (shrink)

MutL family proteins contain an N‐terminal ATPase domain (NTD), an unstructured interdomain linker, and a C‐terminal domain (CTD), which mediates constitutive dimerization between subunits and often contains an endonuclease active site. Most MutL homologs direct strand‐specific DNA mismatch repair by cleaving the error‐containing daughter DNA strand. The strand cleavage reaction is poorly understood; however, the structure of the endonuclease active site is consistent with a two‐ or three‐metal ion cleavage mechanism. A motif required for this endonuclease activity is present (...) in the unstructured linker of Mlh1 and is conserved in all eukaryotic Mlh1 proteins, except those from metamonads, which also lack the almost absolutely conserved Mlh1 C‐terminal phenylalanine‐glutamate‐arginine‐cysteine (FERC) sequence. We hypothesize that the cysteine in the FERC sequence is autoinhibitory, as it sequesters the active site. We further hypothesize that the evolutionary co‐occurrence of the conserved linker motif with the FERC sequence indicates a functional interaction, possibly by linker motif‐mediated displacement of the inhibitory cysteine. This role is consistent with available data for interactions between the linker motif with DNA and the CTDs in the vicinity of the active site. (shrink)

‘Smart’ contrast agents (CA) exhibit dynamic and reversible modulation of their relaxivity by specific physiological or biochemical triggers such as changes in pH, Ca2+ concentration or enzymatic activity (1-3). The extracellular concentration of Ca2+ plays important role in physiological and pathological processes in the nervous system. This led to the designing of a chelating system in which relaxivity is influenced as a function of Ca2+ concentration by changing coordination number around the paramagnetic metal ion. We synthesized a novel bifunctional (...) bismacrocycle [Gd-(DO3A-DTPA- DO3A); Fig.] based on DO3A-EA [{4,7-Bis-carboxymethyl-10-(2-aminoethyl)-1,4,7,10-tetraazacyclododec-1-yl}-acetic acid] coupled to DTPA-bis-anhydride via a flexible alkyl spacer to form the.. (shrink)

As calcium plays an important role in regulating a great variety of neuronal processes, there is a strong interest to generate gadolinium complexes which can act as calcium-sensors in magnetic resonance imaging (MRI). Here we report a new series of potential CAs based on DO3A, having alkylaminobis(methylenephosphonate) side chains (propyl L1, butyl L2, pentyl L3 or hexyl L4). The high complexation efficiency towards the biologically important metal ions of the aminopolyphosphonic acids could be used for the sensing of (...) the extracellular calcium in the brain. On the other hand the introduction of negatively charged phosphonate groups into common Gd3+-based CAs increases their r1 which is important to improve the MR signal especially in high field magnets. The paramagnetic response of the complexes GdL1-GdL4 to Ca2+ was studied by means of relaxometric titrations. The initial relaxivities of the complexes found to be higher than usually reported for the DO3A type ligands at high field magnets (9.4T). r1 values of 6.92, 7.43, 6.70 and 5.76 mM-1s-1 were determined for GdL1, GdL2, GdL3, and GdL4 respectively. Interestingly complexes exhibit unusual properties in the presence of Ca2+. In contrast to previously reported probes the longitudinal relaxivities decrease upon addition of Ca2+. This is favourable for novel fMRI techniques as it could allow transforming the real in vivo decrease in Ca2+ concentration into a positive contrast during physiological processes. The sensitivity of the complexes towards Ca2+ increases with the extension of the aliphatic side chain. No changes in r1 of GdL1 were found over the whole span of Ca2+ concentration. In the case of GdL2, a moderate decrease of r1 was observed on addition of Ca2+, whereas the r1 of the GdL3 and GdL4 solutions showed a strong dependency on the calcium concentration resulting in the decrease to 66% and 61% of the initial r1 values, respectively. (shrink)

The frequency and temperature dependences of the ac conductivity and dielectric constant of the V 2 O 5 -MnO-TeO 2 system, containing two transition-metal ions, have been measured. The dc conductivity † dc measured in the high-temperature range decreases with addition of the oxide MnO. This is considered to be due to the formation of bonds such as V--O--Mn and Mn--O--Mn in the glass. The conductivity arises mainly from polaron hopping between V 4+ and V 5+ ions. (...) It is found that a mechanism of adiabatic small-polaron hopping is the most appropriate conduction model for these glasses. This is in sharp contrast with the behaviour of the Mn-free V 2 O 5 -TeO 2 glass, in which non-adiabatic hopping takes place. High-temperature conductivity data satisfy Mott's small-polaron hopping model and also a model proposed by Schnakenberg in 1968. A power-law behaviour † ac = A y s , with s < 1) is well exhibited by the ac conductivity † ac data of these glasses. Analysis of dielectric data indicates a Debye-type relaxation behaviour with a distribution of relaxation times. The MnO-concentration-dependent † ac data follow an overlapping large-polaron tunnelling model over the entire range of temperatures studied. The estimated model parameters are reasonable and consistent with changes in composition. (shrink)

Structures of multisubunit RNA polymerases strongly differ from the many known structures of single subunit DNA and RNA polymerases. However, in functional complexes of these diverse enzymes, nucleic acids take a similar course through the active center. This finding allows superposition of diverse polymerases and reveals features that are functionally equivalent. The entering DNA duplex is bent by almost 90° with respect to the exiting template–product duplex. At the point of bending, a dramatic twist between subsequent DNA template bases aligns (...) the “coding“ base with the binding site for the incoming nucleoside triphosphate (NTP). The NTP enters through an opening that is found in all polymerases, and, in most cases, binds between an α‐helix and two catalytic metal ions. Subsequent phosphodiester bond formation adds a new base pair to the exiting template–product duplex, which is always bound from the minor groove side. All polymerases may undergo “induced fit” upon nucleic acid binding, but the underlying conformational changes differ. BioEssays 24:724–729, 2002. © 2002 Wiley Periodicals, Inc. (shrink)

In the yeast Saccharomyces cerevisiae three positive transcriptional control elements are activated by stress conditions: heat shock elements (HSEs), stress response elements (STREs) and AP‐1 responsive elements (AREs). HSEs bind heat shock transcription factor (HSF), which is activated by stress conditions causing accumulation of abnormal proteins. STREs mediate transcriptional activation by multiple stress conditions. They are controlled by high osmolarity via the HOG signal pathway, which comprises a MAP kinase module and a two‐component system homologous to prokaryotic signal transducers. AREs (...) bind the transcription factor Yap1p. The three types of control elements seem to have overlapping, but distinct functions. Some stress proteins encoded by HSE‐regulated genes are necessary for growth of yeast under moderate stress, products of STRE‐activated genes appear to be important for survival under severe stress and ARE‐controlled genes may mainly function during oxidative stress and in the response to toxic conditions, such as caused by heavy metal ions. (shrink)

We considered peculiarities of the evolution of a region with sharp boundaries that is filled with a partially ionized plasma and is a part of the volume of a condensed target. The creation of such a region in the near-surface layer of the target can be related to the action of an external impulse symmetric ionizator or to the action of an intense small-extension shock wave on the target surface. We defined the conditions such that their fulfilment during the establishment (...) of the equilibrium between the Coulomb attraction of electrons and ions with atom ionization multiplicity Z* 1 and the kinetic pressure of electrons causes both the compression of this region and its ionization to the state with Z* 2 > Z* 1. The last leads to a further additional compression and ionization. Under these conditions, the spontaneous avalanche-like ionization of atoms of the target to the state of ‘‘bare’’ nuclei occurs synchronously with the avalanche-like metallization and the self-compression of the target. We showed that the avalanche-like ionization and the self-compression of the target happen in the case where the gas of degenerate electrons has drift momentum. If the region with initial ionization has the form of thin spherical layer, the process of avalanche-like ionization and self-compression of the target in this region is accompanied by the accelerated movement of the plasma layer to the target center. One of the reasons for the accelerated movement is the surface tension in a bounded domain of the nonequilibrium plasma layer neutralized by ions of the target. With increase in the velocity of movement of this layer to the target center, the additional self-compression of the system of electrons and nuclei to the state of degenerate electron gas occurs. At the leading edge of the running layer with extremely high electron density which is neutralized by nuclei of the target, the formation of a collapse of the electron--nucleus system proceeds, and the binding energy maximum for the electron--nucleus system shifts from A≈60 to A ≫ 60. This result makes possible the fast synthesis of superheavy nuclei. The decay of the collapse state, a partial restoration of the target structure, its rapid cooling, and the condensation of a part of the products of nuclear reactions happen in the target volume at the trailing edge of the moving plasma layer. Upon such a scanning propagation of the wave with high electron density, all the target substance is involved, step-by-step, to the process of nuclear transformations. At the target center, the moving plasma layer is squeezed with the formation of the state of quasistationary collapse under inertial confinement. Then the collapse state decays irreversibly. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Extractivist OntologiesLithium Mining and Anthropocene Imaginaries in Chile's Atacama DesertMauricio F. Collao Quevedo (bio)The term energy transition generally refers to efforts to switch from one energy system to another. In light of the current climate crisis, energy transition projects have sought to move societies away from their reliance on fossil fuels and toward a renewables-based energy system. Yet such projects have not been easy to undertake. As Marie Forget (...) and Vincent Bos point out, an energy system based on renewables requires a transformation of energy "regulatory frameworks, technical and organizational structures, geographic forms and network practices" (1). More specifically, current energy transition models rely on the expansion of lithium production, accompanying systems of private property rights, and complex logistical and technical strategies. This article examines the interplay between lithium extraction, national development, and Anthropocene imaginaries in Chile's Atacama Desert, arguing that the green brand of extractivism that characterizes the industry relies on elaborate institutional arrangements aimed at expanding and protecting extractivist ontological and epistemological regimes in the politically contested region. As such, struggles over lithium in Chile's Atacama region demonstrate the extent to which efforts to decolonize the Anthropocene and make possible non-extractive futures of collective survival must unfold on ontological grounds, against the consolidation of the Age of Man.Mining, Water Rights, and Indigenous Communities in the Atacama DesertAmong today's most promising energy sources and materials are sodium, copper, sulfur, nickel, cobalt, rare earth metals, and lithium. These [End Page 78] have become central to energy transition strategies and states seeking to attract investors for development (Lunde Seefeldt). As a report by the World Bank points out, demand for transition minerals like lithium, cobalt, and graphite could increase by 500% by 2050 ("Climate-Smart Mining"), highlighting the extent to which global energy transition efforts are counting on greater extraction of transition minerals and the expansion of extractive frontiers to previously unexplored or unexploited regions (Moore, Capitalism; World Bank Group). Lithium is at the center of this economic and technological shift toward green economies.Global lithium demand is growing rapidly, with investment and production rates growing significantly in recent years (Narins) and catching the attention of states (e.g., China) and corporate tech giants (e.g., Tesla) that are already trying to secure greater shares of the global market. The light metal's popularity is largely due to its internal chemistry, which meets many of the technical and practical requirements associated with green energy transition. Lithium is light, conducive, and energy-dense, which in the context of batteries means faster recharge, lower costs, and charge-holding abilities that make lithium-ion batteries more efficient than a nickel-metal hybrid equivalent (Perotti and Coviello). Because of this, lithium is increasingly being considered as promising for human development and survival as its energy predecessors, inspiring labels such as "white gold," "white petroleum," "the new copper," "the 21st century's petroleum," or the "new gasoline" of sustainability (Acuña and Tironi; Lunde Seefeldt; Voskoboynik and Andreucci).But the industry is not without its downsides. The negative impacts of lithium extraction in Chile's Atacama Desert have been challenged by local communities for whom the metal does not exist as a discrete entity that can be easily extracted from its socioecological context. For many of these communities, lithium is more than a transition metal found in an appropriable and materially heterogenous underground brine: it is an ontologically contested, socioecological entity that sustains and participates in complex webs of life-supporting, place-based, and more-than-human relations. Such accounts of the brine are radically incompatible with "official" state accounts of it, which are maintained through an institutional architecture that allows the ontological basis of the brine to be manipulated for extractive purposes by both corporate and state actors.In the following pages, I examine the ways in which Chile's legal and institutional arrangements, informed by imaginaries of green modernization, [End Page 79] create conditions under which extralocal actors can manipulate along extractivist lines the ontological ambiguity and material heterogeneity of lithium-containing brines in the salt flats of the Atacama Desert. Through an analysis of the ways in which lithium industries in the... (shrink)

The first electron back-scattered diffraction Kikuchi patterns and grain orientation maps were captured for pure n -phase Ce. The sample preparation technique used for electron back-scattered diffraction orientation mapping of this surface-reactive metal included ion sputtering the surface using a scanning Auger microprobe followed by vacuum transfer of the sample from the scanning Auger microprobe to the scanning electron microscope. The effect of ion sputtering on the microstructure as well as preliminary electron back-scattered diffraction microstructural characterization is presented. Based (...) on the sputtering data, the room-temperature diffusivity of O in n -Ce was estimated. (shrink)

MĂDĂLINA DIACONU, Tasten, Riechen, Schmecken. Eine Ästhetik der anästhesierten Sinne, 2005 ; SILVIA STOLLER, VERONICA VASTERLING,LINDA FISHER, Feministische Phänomenologie und Hermeneutik, 2005 ; KARL SCHUHMANN, Karl Schuhmann: Selected Papers on Phenomenology. Edited by CEES LEIJENHORST and PIET STEENBAKKERS, 2004 ; HIROSHI GOTO, Der Begriff der Person in der PhänomenologieHusserls. Ein Interpretationsversuch der Husserlschen Phänomenologie als Ethik im Hinblick auf den Begriff der Habitualität, 2004 ; GÜNTER FIGAL, Lebensverstricktheit und Abstandsnahme. „Verhalten zu sich“ im Anschluss an Heidegger, Kierkegaard und Hegel, 2001 (...) ; JACQUES DERRIDA, Le toucher, Jean-Luc Nancy, 2000. (shrink)

The emergence in Britain of chemical engineering, by mid‐century the fourth largest engineering specialism, was a hesitant and drawn out process. This article analyses the organisational politics behind the recognition of the technical occupation and profession from the First World War through to the end of the 1920s. The collective sense of professional identity among nascent ‘chemical engineers’ developed rapidly during this time owing to associations which promoted their cause among potential patrons. -/- .

On intellectual foundations that distinguished chemical engineering from other disciplines.

Chemical engineering - as a recognised skill in the workplace, as an academic discipline, and as an acknowledged profession - is scarcely a century old. Yet from a contested existence before the First World War, chemical engineering had become one of the 'big four' engineering professions in Britain, and a major contributor to Western economies, by the end of the twentieth century. The subject had distinct national trajectories. In Britain - too long seen as shaped by American experiences - the (...) emergence of recognised chemical engineers was the result of professional aspirations and contingency, and shaped by a shifting ecology of institutions, firms and government. Drawing upon extensive archival research, this book examines the evolution of technical practice, working environment and social interactions of chemical engineering. It will be of considerable interest to historians, sociologists of the professions, and to practitioners themselves. (shrink)

In this paper, we present two proofs of the reciprocal butterfly theorem. The statement of the butterfly theorem is: Let us consider a chord PQ of midpoint M in the circle Ω(O). Through M, two other chords AB and CD are drawn, such that A and C are on the same side of PQ. We denote by X and U the intersection of AD respectively CB with PQ. Consequently, XM = YM. For the proof of this theorem, see [1]. The (...) reciprocal of the butterfly theorem has the following statement: In the circle Ω(O), let us consider the chords PQ, AB and CD which are concurrent in the point M≠O, such as the points A and C are on the same side of the line PQ. Let X and Y respectively be the intersections of the chord PQ with AD and BC respectively. If XM = YM, then M is the middle of the chord PQ. (shrink)

Since its inception philosophical thought has been fixated by death. Death, as much as life, has been the unrelenting driving force behind some of history’s greatest thinkers. Yet, for Emil Cioran, a Romanian-French philosopher, even philosophy cannot attempt to understand nor contain the inevitable unknown. Considered to be an anti-philosopher, Cioran approached and reflected on the human experience with a despairing pessimism. His works are characterised by a brooding, fatalistic temperament that reveals and defines itself in his irony, black humour (...) and inimitable style. Although Cioran’s later works have received much scholarly recognition, little attention has been paid to the texts he wrote in his adolescent. Grounded in the historical context of interwar Romania, this book presents for the first time an analysis of the little-known works of this pioneering Romanian thinker. Deeply affected by his upbringing, this book offers a glimpse into Cioran’s first attempts to delve into philosophical enterprise, before turning its attention to his later works, On the Heights of Despair (1934), The Transfiguration of Romania (1936) and Twilight of thoughts (1940; written in France). Using both the French and Romanian editions of these works, but also their original manuscripts, this volume seeks to provide a re-reading that takes language rather than a social or political critique as its focal point. As an important and provocative contribution to the existing literature on Cioran, this book will be an essential point of reference for students and researchers, alike. (shrink)

This book is a rediscovery and examination of the thinking of Vasile Băncilă, a philosopher forbidden by the totalitarian regime of Nicolae Ceaușescu. The philosopher Lucian Blaga saw Băncilă as a threat to the spirit of the highest Romanian culture. It is estimated that Băncilă's work extends to 32 volumes, 17 of which have been published so far. With such a significant opus, Vasile Băncilă is, indisputably, a key figure in contemporary Romanian culture, particularly in the sphere of philosophy. The (...) book has eleven chapters and is divided into two parts. The first part deals with the hermeneutics of the author's youthful works. His reflections on the purpose of philosophy for life are important, about the role of this discipline in the education of adolescents and students, the relationship between irony and education, his thoughts of one of the greatest Romanian poets, Mihai Eminescu, and the philosophy of Descartes and of Schopenhauer. In the second part, the book looks at Băncilă's aim of structuring a possible system of philosophy; more precisely, an ethnic-spiritualist metaphysics which, when it was elaborated, contradicted the official ideology of the totalitarian regime. Finally, the book covers the philosopher's work, analysing step-by-step the relation between the part and the whole (pars pro toto), as well as between existence and metaphysics, and the philosopher's conclusions about Romanian existence. (shrink)

The present study aims to carry out an analysis of the relation between the Bibles of Samuil Micu and Andrei Șaguna from an isagogic perspective, with a particular focus on the canon and canonicity of the books of the Holy Scripture. We believe that, through such an analysis, we can observe what they have in common, but also what differentiates the two Transylvanian editions of the Holy Scripture so that we can help those interested in understanding the reasons behind the (...) current controversies as to the relation between them. Although these controversies refer to the biblical text of the two Scriptural editions, the fact that the attitude towards it was caused by denominational factors, whose doctrinal background is represented by two different traditions of understanding the biblical canon, has been overlooked. This is why we find that the evaluation of how the two Romanian editions of the Holy Scripture (the Bible of Samuil Micu, 1795, and the Bible of Andrei Șaguna, 1856-1858) relate to the canonical tradition of each Church and cultivate their isagogics is fundamental for the establishment and understanding of the relation between them. (shrink)

In this commentary, I will argue that the componential and emergent views of cognitive control as defined by Cooper (2010) do not necessarily oppose each other, and I will try to make a case for their interdependence. First, I will use the construct of cognitive inhibition—one of the main componential control functions mentioned in the target articles—to illustrate my line of reasoning. Then, I will comment on how some of the target articles, each from a different perspective, bring arguments in (...) favor of this integrative view. (shrink)