Destacats

Cada any, un comitè d'experts s'ha d'enfrontar a la difícil tasca d'escolllir, d'entre totes les publicacions ICREA, unes poques que destaquin sobre la resta. És tot un repte: de vegades els debats s'acaloren, i sempre són difícils, però acaba sortint-ne una llista de 24 publicacions. No es concedeix cap premi, i l'únic reconeixement addicional és l'honor d'ésser presentat com a Highlight. Cada publicació té alguna cosa especial, sia una solució especialment elegant a un vell problema, un resó espectacular als mitjans de comunicació o simplement, la fascinació d'una idea revolucionària. Independentment del motiu, es tracta dels millors dels millors i, com a tals, ens plau compartir-los aquí.

LIST OF SCIENTIFIC HIGHLIGHTS

Format: 2018
  • Efficient device-independent entanglement detection for multipartite systems (2017)

    Acín Dal Maschio, Antonio (ICFO)

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    Entanglement is a form of correlations observed among quantum particles that does not have a classical analog. It is also one of the most studied properties of quantum mechanics for its application in quantum information protocols. Detecting its presence in systems with many particles, however, remains experimentally and theoretically challenging. The first barrier is the exponential amount of information required to reconstruct the system’s state. The second is that, even if the quantum state is known, the available methods are computationally too demanding even for systems composed of few particles.

    In our work, we introduce a new technique for entanglement detection that provides significant advantages with respect to previous methods. First, it scales efficiently with the number of particles, thus allowing for application to systems composed by up to few tens of particles. Second, it needs only the knowledge of a subset of all possible measurements on the state, therefore being apt for experimental implementation. Moreover, since it is based on the detection of Bell inequality violations, our method is device independent, meaning that it allows one to assess entanglement without assuming any prior knowledge of the prepared state or the measurements performed. We report several examples of its implementation for well-known multipartite states, showing that the introduced technique has a promising range of applications.

    We expect our findings will contribute to advancing the field of entanglement detection towards larger systems. In particular, this new approach can supersede the current methods used to detect entanglement in state-of-the-art experiments involving tens of particles.

  • Hematite-based nanowire structures to enhance solar-to-fuel conversion in photoelectrochemical water splitting (2017)

    Arbiol, Jordi (ICN2)
    Galán-Mascarós, José Ramón (ICIQ)

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    ICN2 researchers led by ICREA Prof. Jordi Arbiol, in collaboration with the IREC and ICIQ, have produced a material for use in photoelectrochemical water splitting that is not only cheaper than existing alternatives, but increases both the efficiency and output of the process. Based on the integration of several materials into a multilayer nanowire structure, the research was featured on the October's cover of Energy & Environmental Science.

    Photoelectrochemical (PEC) water splitting is a process whereby sunlight is harnessed in combination with specialised semiconductor materials to induce electrolysis and separate the hydrogen from the water molecule. With global climate change driving the need to find more efficient sources of sustainable energy, it is a topic that has received much attention over recent years. What ICN2 researchers have done, in collaboration with IREC and ICIQ, is to optimise the properties of the semiconductor material for a more efficient and productive solar-to-fuel conversion.

    Specifically, the semiconductor material is needed to absorb the solar energy and act as an electrode in the water splitting process. Hematite, a common semiconductor with a narrow bandgap ideally-suited to absorbing the solar spectrum, is a known candidate for this function as “photoanode”. As an iron oxide (α-Fe2O3), hematite is among the most abundant minerals on Earth’s surface and so is considerably cheaper than the gold and platinum typically used. However, issues relating to the flow of electric charge (namely, poor charge transport, surface charge recombination and slow charge transfer kinetics) have limited its practical application in PEC water splitting.

    To overcome these limitations, previous studies have focused on the development of hematite composites, structures which incorporate a second material that lends compensatory or augmentative properties to the hematite base. What ICREA Prof. Jordi Arbiol and his team have done is to integrate four materials into a multilayer nanostructure and systematically study the PEC performance of the resulting photoanode, also shedding light on the underlying chemical mechanisms.

  • Circadian reprogramming, rather than circadian arrhythmia, underlies stem cell and tissue ageing.  (2017)

    Aznar Benitah, Salvador (IRB Barcelona)
    Muñoz-Cánoves, Pura (UPF)

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    It has been historically posited that we lose our circadian rhythms as we age, and that circadian arrhythmia is one of the underlying causes of ageing. We decided to study whether this was true, and what is the precise connection between circadian rhythms and tissue ageing. In these two papers, we therefore studied in an unprecedented depth how circadian rhythms are affected during aging of different adult stem cells (epidermis and muscle), and metabolic tissues, such as the liver. We show that aged stem cells and aged liver unexpectedly remain perfectly rhythmic, yet their circadian output (that is, all the functions whose timing is regulated by the clock) becomes reprogrammed to cope with age-related tissue-specific stresses. Importantly, in doing so, the clock stops imposing a correct timing of stem cell and tissue function, which further exacerbates aging. Importantly, we find that this reprogramming is significantly prevented by caloric restriction. We believe this is the first comprehensive analysis of how the clock behaves in aged stem cells and tissues. These studies importantly indicate that circadian reprogramming, rather than circadian arrhythmia, underlies the process of tissue ageing, and highlight the importance of how systemic metabolic cues derived from our diet impinge in tissue and organismal ageing. 

     

  • Identification of the cells that generate metastasis, and how they depend on dietary fatty acids.  (2017)

    Aznar Benitah, Salvador (IRB Barcelona)
    Di Croce, Luciano (CRG)

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    Metastasis is the leading cause of cancer-related deaths, yet the identity of the cells responsible for metastatic spreading has remained historically elusive. In this work, we identified metastasis-initiating cells (MICs) in several types of human tumors.  We show that MICs: (i) are exclusive in their ability to generate metastases when transplanted; (ii) intriguingly, they express the fatty acid channel CD36 and have a prominent lipid metabolic signature; (iii) are exquisitely sensitive to the levels of fat in circulation, thus providing a link between the predisposition of metastasis and dietary fat; (iv) are highly sensitive to CD36 inhibition, which almost completely abolishes their metastatic potential; and (v) operate in many different types of human tumors. This work is allowing us to characterize metastatic cells in an unprecedented manner, and helping us develop therapies targeting lipid metabolism with specific anti-metastatic potential. 

  • Structural stability: an essential property of protein-ligand complexes with implications for drug discovery (2017)

    Barril Alonso, Xavier (UB)

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    Rational drug discovery aims to discover and optimize molecules that bind to, and modulate the behaviour of, therapeutic targets in the most effective and efficient manner. Existing methods aim to predict the binding affinity of a given molecule for its target, but this property is notoriously difficult to compute and lack of correlation between computed and experimental values is more the norm than the exception. In this work we propose an alternative view of protein-ligand complexes, enabling us to develop a method for the identification of drug candidates that is conceptually new and computationally efficient.

    Starting from the observation that protein-ligand complexes are structurally stable, we hypothesise that this property (i.e. the ability to maintain a well-defined binding mode) can be primarily attributed to certain key hydrogen bonds. To probe this idea, we devised Dynamic Undocking (DUck), a fast computational procedure that quantifies the work necessary to break those particular interactions (WQB). The results demonstrate that active molecules form interactions that are hard to break, while this is not the case for the majority of inactive molecules. In consequence, DUck is a very effective method for virtual ligand screening.

    More importantly, this work opens a different perspective on protein-ligand complexes. Besides looking at the situation of equilibrium – where two molecules make the best possible interactions – we must also consider which are the breaking points, how the complex will come apart and how we can improve the drug by making it more resistant to structural distortions. In fact, we demonstrate that Dynamic Undocking is orthogonal with existing (thermodynamic) approaches, and optimal results are obtained when both types of methods are combined.

    Prospective validation of the method has led to the discovery of novel bioactive molecules for which the binding mode has been confirmed experimentally. The method is freely available for the wider scientific community and we are applying it to various internal and collaborative projects.

  • New approaches to investigate cause of death in poor countries (2017)

    Bassat, Quique (ISGlobal)

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    In spite of large efforts and generous investments, mortality statistics and cause of death estimates from poor countries remain, as of today, still unreliable. In these settings, where the majority of preventable deaths still occur, models utilized to build estimates have shown many flaws, and discrepancies in cause-attributable disease figures have evidenced the shortfall of current methods, predominantly based on data derived from verbal autopsy or clinical records. With efforts targeting the improvement of civil and vital registration systems, counting the dead has become progressively easier, but establishing the cause of death for each person remains a major challenge, particularly among children. Routine and cause-specific disaggregated mortality data are however critical at the local level to help policy makers make rational health planning and prioritisation decisions.

    Pathological autopsies are generally considered the gold standard methodology to investigate cause of death, but their practice is globally decreasing, and in the majority of poor settings their routine use and acceptability is severely limited. In the last years, we have developed and validated a less invasive, but similarly informative methodology that, using fine needle biopsies, can sample key tissues and organs after death, thus providing rich pathological and microbiological samples to investigate the cause of death.

    We have also demonstrated that such a method is readily acceptable at the community level, even in rural African settings, and that it can be utilized “in the field” to conduct robust mortality surveillance. The Minimally invasive autopsy will surely contribute, as no other method has made until now, to increase our understanding of the major determinants of preventable mortality, and the enormous inequities that surround survival in resource-constrained settings.

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