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The majority of bacterial gene regulators bind as symmetric dimers to palindromic DNA operators. Multimeric forms of proteins, including tetramers, are able to recognize longer operator sequences in a cooperative manner, although how this is achieved is not well understood due to the lack of complete structural information. Using data collected at Diamond Light Source beamline I04, we solved the crystal structures of the multidrug binding protein TtgV, a gene repressor that controls efflux ...
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There are literally astronomical numbers of bacteriophages on Earth. These are viral parasites of bacteria and as such generate an immense selective pressure, driving adaptive co-evolution between predator and prey. Bacterial hosts are forced to evolve protective mechanisms1 whilst the predating phages must respond to subvert these new counter-measures. One broad class of phage-resistance mechanisms takes an extreme approach, causing the suicide of phage-infected bacteria before the ...
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The intricate wiring of the human brain requires cell surface signalling systems to guide the growing neurites to their correct locations. Indeed, the development and homeostasis of tissues throughout the body is founded on cell guidance systems. The semaphorins constitute one of the major families of cell guidance cues and with their cognate receptors, the plexins play central roles in diverse physiological processes ranging from cell migration, angiogenesis and neural connectivity to ...
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G protein coupled receptors (GPCRs) are a large family of proteins that span the cell membrane of eukaryotes and consist of seven transmembrane helices. GPCRs respond to molecules outside the cell and activate signal transduction pathways inside the cell. The adenosine receptor and β-adrenoceptors (βARs) are GPCRs that activate intracellular G proteins in response to the binding of agonists like adenosine or noradrenaline, respectively. The importance of agonist-induced activation of ...
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Optimizing the electronic and magnetic properties of layered magnetic heterostructures for specific applications remains a challenging task for materials engineering. Characterization techniques employing the absorption and scattering of soft X-rays have emerged as important and powerful tools for the study of heterostructures and their interfaces. In fact, magnetic dichroism in X-ray absorption (XA) i.e., the difference in absorption based on the relative orientation of the X-ray ...
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The spin-torque resonance effect on domain walls is an exciting new line of research for spintronic devices such as race-track memory and magnetic logic as it allows depinning of domain walls from pinning sites at lower threshold current densities. Following the initial observation of domain wall resonance using an oscillating current in a semicircular Ni80Fe20 (Py) wire 1 where the restoring force was provided by an applied magnetic field perpendicular to the wire, further work has shown an ...
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All living cells require energy, usually provided in the form of ATP, to carry out fundamental processes like movement and growth. Therefore, cells have to balance energy supply with the demand. AMP-activated protein kinase (AMPK) has emerged as a central component of a signalling pathway involved in regulating intracellular energy homeostasis. When ADP and AMP levels increase, concomitant with a fall in ATP levels, AMPK is activated by phosphorylation on threonine-172 within the catalytic a ...
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The anaphase promoting complex or cyclosome (APC/C) is a multi-subunit cullin-RING E3 ubiquitin ligase that functions to regulate progression through the mitotic phase of the cell cycle and controls entry into S phase 1. APC/C-mediated coordination of cell cycle progression is achieved through the temporal regulation of APC/C activity and substrate specificity. The core APC/C is assembled from 13 different proteins, mostly highly conserved and essential for function, generating a ...
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Liquid crystals have transformed our daily lives, with the LCD industry currently being worth £300 bn per year worldwide. The nematic phase, the most common LC phase used in displays and also the simplest, is formed by rod-like aromatic molecules bearing a flexible chain at one or both ends. Such molecules also form layered, or smectic, phases (Fig. 1, left). Thirty years ago a third type of LC, the columnar phase, was discovered in disc-like molecules, with columns of stacked discs placed ...
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Organic photovoltaic (PV) materials have long-term promise for large area devices on flexible substrates produced by low-cost processes such as inkjet printing. Control of order and morphology at the nanometre scale during processing steps such as thermal annealing is crucial for optimized device efficiency. In this study, the structural changes during in-situ annealing are characterised by time-resolved grazing incidence X-ray diffraction.
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Our society takes for granted the high performance aluminium alloys used in aircraft, trains, fast ferries and motor vehicles. This high performance exists thanks to extensive research and development in industry and academia. One part of that research involves studying alloys as they solidify. During solidification, an alloy is a semi-solid “mush”, with properties that will significantly affect the quality of the final solid material. One property of great importance is the formation of ...
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Synchrotron applications such as coherent X-ray diffraction and X-ray photon-correlation spectroscopy require detectors with a very small pixel size. Furthermore, the detector should have a high frame rate, large dynamic range, high detection efficiency and be also radiation hard. The Medipix range of readout chips (Medipix2 and Medipix3), with a pixel pitch of 55 µm, emerged as good candidates to develop a large area detector for the aforementioned applications. However, reducing the pixel ...
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Solid-state materials, particularly those performing useful functions (e.g. zeolites), often form frameworks or cellular structures on the nanoscale1. These frameworks are usually rigid. Liquid crystals (LC), on the other hand, have a capacity to change shape and respond to external stimuli, such as pH or temperature, and offer the prospect of forming responsive cellular structures. T-shaped block molecules bearing three types of mutually incompatible groups (triphilic) were found to ...
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Magnetic recording lies at the heart of many modern electronic devices. The density at which information can be stored is directy related to the size of the magnetic particles within the storage devices. In order to increase the recording density one must reduce the size of the magnetic particles. Unfortunately, there is a problem: the superparamagnetic limit. Below this size, the magnetization can change direction randomly, driven by thermal fluctuations. Heat assisted magnetic recording1 ...
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Despite decades of study, the mechanisms that HIV employs at certain steps of its replication cycle remain relatively nebulous. One such step involves the viral regulatory protein, Rev, whose principal function is to affect the nuclear export of a majority of the viral mRNA transcripts that are produced during infection. Rev achieves the specific transport of the viral RNAs by oligomerizing onto the Rev response element, a highly-structured RNA motif within an env intron. Without such RNA ...
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The proton dependent oligopeptide transporters (POTs) are a large family of integral membrane proteins that use the inwardly directed proton electrochemical gradient to transport small peptides, amino acids and nitrate across cellular membranes in both pro- and eukaryotic cells. Evolutionarily the POT family sits within the much larger Major Facilitator Superfamily (MFS), members of which contain a common structural motif of 12 transmembrane-spanning alpha-helical segments. The human genome ...
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Rhomboids belong to the family of intramembrane proteases that use a catalytic dyad of serine and histidine for proteolysis of substrate transmembrane proteins. Conserved in both prokaryotes and eukaryotes, they regulate diverse cellular processes such as intercellular signalling, parasitic invasion of host cells, and mitochondrial morphology. Their importance in biology provides a strong incentive to understand the mechanism of these unusual enzymes for identification of specific ...
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Diamond is one of the most interesting materials for many applications in engineering, electronics, jewellery, and synchrotron radiation instrumentation. Chemical vapour deposition techniques allow diamond growth on a range of substrates, and in a range of crystalline quality. Nano-crystalline diamond has been proposed for use in biosensors and nanolithography as it can be deposited with sub-µm resolution. X-ray optics made of diamond are almost transparent, very strong, and are subject to ...
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The relentless drive for greater information storage capacity in physically smaller devices has pushed the size of components to scales where quantum mechanical effects become important. To aid such an increase in information density, both the electron spin and charge are exploited in the field of spin transport electronics; hence the portmanteau spintronics. The idea is to combine the characteristics of existing magnetic devices with semiconductor devices in order to realise a new ...
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Spintronic devices make use of the electron spin to store, recall and process data. Examples include the spin-valve read head, which has produced orders-of-magnitude improvements in magnetic data storage densities, and cutting-edge nonvolatile magnetic random access memory. Over the past decade, ferromagnetic (FM) semiconductors have emerged as new candidates for spintronic applications, offering the prospect of combining high density storage and gate-controlled logic in a single material.1 ...
