Highlights

Every year, a committee of experts sits down with a tough job to do: from among all ICREA publications, they must find a handful that stand out from all the others. This is indeed a challenge. The debates are sometimes heated and always difficult but, in the end, a shortlist of  the most outstanding publications of the year is produced. No prize is awarded, and the only additional acknowledge is the honour of being chosen and highlighted by ICREA. Each piece has something unique about it, whether it be a particularly elegant solution, the huge impact it has in the media or the sheer fascination it generates as a truly new idea. For whatever the reason, these are the best of the best and, as such, we are proud to share them here.

LIST OF SCIENTIFIC HIGHLIGHTS

Format: yyyy

  • Closing the Door on Einstein and Bohr’s Quantum Debate (2015)

    Mitchell, Morgan W. (ICFO)
    Pruneri, Valerio (ICFO)

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    Closing the Door on Einstein and Bohr’s Quantum Debate

    Quantum mechanics makes extraordinarily accurate predictions, but has internal workings so counter-intuitive that many refuse to believe they represent reality. Among these non-believers was Albert Einstein, who, starting in 1927, carried on an extended debate with Niels Bohr, a towering figure in quantum theory. In 1935 Einstein argued for the creation of a theory that was compatible with both the Theory of Relativity, in which the speed of light is a fundamental limit, and with realism, the idea that our observations reflect a reality independent of ourselves. This position, now called “local realism,” directly opposed Bohr's arguments for the uncertainty principle.  The debate between these two giants of physics was never settled. In 1964, CERN researcher John Stuart Bell showed that an experiment could resolve this seemingly philosophical question.  Bell analyzed the following scenario: pairs of particles are sent to widely-separated measurement stations, where one property of each particle is measured.  The measurements are chosen randomly and performed simultaneously.  If the particles show sufficiently well-correlated behaviour, Bell proved, something in local realism must be wrong: Either the particle properties had no prior existence, or particles can communicate with each other faster than light (or both).  Starting in 1972, a sequence of experiments have approximated Bell's scenario with increasing sophistication.  Until this year, however, all experiments contained weaknesses, or “loopholes,” allowing alternate explanations.  For example: not performing the measurements fast enough, not measuring enough of the particles, or not choosing sufficiently randomly.  This year, three experiments: at TU Delft, IQOQI (Vienna), and NIST (USA), succeeded in simultaneously closing all of the closable loopholes, and in doing so solidly rejected local realism. 

    This work was the result of three collaborations:  TU Delft - ICREA - ICFO - Element 6, IQOQI - U. Vienna - MQP - Linköpings U. - ICREA - ICFO - PTB - NIST, and NIST - IQC - U. Illinois - U. Moncton - JQI - JPL - ICREA - ICFO - CIAR

  • New Fossil suggests we had a Gibbon-like Early Ancestor (2015)

    Moyà Solà, Salvador (ICP)

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    New Fossil suggests we had a Gibbon-like Early Ancestor

    The evolutionary history of extant gibbons (Hylobatidae, Hominoidea, Primates) or Lesser Apes, is probably one of the most enigmatic problems in primate evolution. The absence of fossil evidence to show when and where the gibbon lineage emerged is the major difficulty. However, recent fieldwork in the extraordinary Catalan Miocene fossil record -the most complete of the Eurasian continent in respect to hominoid evolution- provided a partial skeleton composed of 70 specimens in one of the sites of the stratigraphic series of Abocador de Can Mata (els Hostalets de Pierola, Barcelona). These include most of the skull and dentition, as well as a considerable portion of the left arm, including several elements of the elbow and wrist joints. The analysis of the new finding, allowed the description of a new genus and species of extinct hominoid, Pliobates cataloniae. They belong to an ape of similar size to that of the smallest living gibbons (4 to 5 kg), which lived 11.6 million years ago. Pliobates shows, for the first time in a fossil primate of this size, a set of characteristic features of extant hominoids, presumably inherited from their last common ancestor, which probably lived in Africa several million years before Pliobates.

    This find radically changes the hitherto accepted morphotype of the hylobatid-hominid ancestor and provides very solid clues about the origin of extant gibbons. All the small-bodied (5 to 15 kg) fossil anthropoids found before Pliobates are too primitive to be closely related to extant hominoids. Although Pliobates retains some primitive characters, the arm anatomy and, in particular, the joint between the humerus and radius as well as the wrist bones already possess the basic design of living hominoids. A phylogenetic analysis, based on more than 300 characters, very consistently places Pliobates as the stem hominoid closest to the divergence between lesser and great apes, and suggests that the last common ancestor of extant hominoids might have been more similar to living gibbons than to great apes. Furthermore, the skull and some parts of the postcranial skeleton show some features that are exclusive of extant gibbons.

  • CO2 sequestration in the deep Pacific Ocean during glacial times (2015)

    Pelejero Bou, Carles (CSIC - ICM)

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    CO2 sequestration in the deep Pacific Ocean during glacial times

    The cause of the characteristic variability in atmospheric CO2 over glacial-interglacial timescales has been under debate since its discovery in the 1980s. Initially based on the study of Antarctica ice cores, an intriguing parallelism was found between atmospheric CO2 and global temperature, with high CO2 levels during warm interglacial periods, and low CO2 concentrations during cold glacial times. Even though the oceans have often been put forward as the main responsible for this parallelism, their role in sequestering and releasing CO2 and the mechanisms behind this still remains an open question. In this study, we analyzed the evolution of the ventilation of the Eastern Equatorial Pacific waters over the past 25,000 years aiming at detecting the existence of old water masses which could explain a possible CO2 sequestration in the deep ocean. To this end, we analyzed the radiocarbon (14C) preserved in the shells of benthic and planktonic foraminifera fossils accumulated in a deep sea sediment core retrieved in this area. These data demonstrated the existence of a mass of deep water that, during glacial times, was about 1,300 years older than the same water mass today. With the start of the deglaciation, the radiocarbon signal indicated a reactivation of the ocean circulation, coinciding with the increase in atmospheric CO2 documented in ice cores. Altogether, these results support the hypothesis that the deep oceans, particularly the Pacific Ocean, stored vast amounts of CO2 during the last glacial period, which was released during the deglaciation. These results lend support to the important role of the deep ocean and ocean ventilation in regulating the atmospheric concentration of CO2 at glacial/interglacial timescales. Over the last decade, the oceans have been absorbing approximately 26% of the anthropogenic emissions of CO2. The oceans have been a key element in controlling atmospheric CO2 levels in the past and at present, and they will certainly also play a very significant role in the future, a role that will be constrained more accurately with data from paleoreconstructions such as this one.

  • On genetic differentiation between domestic pigs and Tibetan wild boars. (2015)

    Pérez Enciso, Miguel (UAB)

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    On genetic differentiation between domestic pigs and Tibetan wild boars.

    In this work, Pérez Enciso et al. challenge the conclusion from a previous report on Tibetan pigs by Li et al. (2013), which claimed that Tibetan pigs had diverged from other pigs several million years ago. Perez-­Enciso et al. reanalyzed that and other public data from 65 complete pig genomes to prove that Tibetan pigs are no more divergent than any other Chinese breed, thus resetting the landscape for pig evolutionary studies. This report was accompanied by another one by Frantz et al. who, using completely different arguments, reached the same conclusion and, together with another paper on Chinese pig genomes, was featured in the Nature Genetics cover.

  • High relevance of asymptomatic individuals for malaria propagation and the dual role of climate in endemic and epidemic settings in Africa. (2015)

    Rodó i López, Xavier (IC3)

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    High relevance of asymptomatic individuals for malaria propagation and the dual role of climate in endemic and epidemic settings in Africa.

    A new study published in the Proceedings of the National Academy of Sciences of the United States of America by scientists from CONICET Bariloche, Institut Pasteur both at Paris and Dakar, IRD-Dakar and the Institut Català de Ciències del Clima (IC3) at Barcelona, shows unequivocally how the incidence of clinical malaria is both influenced by climatic factors and immunity. Disentangling the relative contributions of these factors is a major challenge. The study benefits from a unique long-term follow-up of 2 adjacent populations spanning two decades in Senegal, that have very different levels of malaria endemicity. By using  recently developed mathematical modelling techniques and extremely detailed records from both malaria incidence, parasite inoculation variability within hosts by mosquito population, and local climate data, the study was able to demonstrate how the influence of immunity and climatic factors varies according to the force of infection. A common modelling framework elucidates important information on how immunity influences transmission of the parasite from men to mosquitoes. Notably, the models show how individuals, who are infected without symptoms or infected with parasites at an undetectable level by classical diagnostic methods, contribute significantly to the infectious population. Undetectable but infectious individuals are likely to present a problem for elimination of the parasite reservoir in humans, which is the final step towards elimination of the malaria in a population.

  • Quantum analyses reveal secrets of wiggly sugars (2015)

    Rovira Virgili, Carme (UB)

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    Quantum analyses reveal secrets of wiggly sugars

    Carbohydrates are critical macromolecules in biochemistry and cell biology, notably in immunity and intercellular communication. Enzymes that help build, degrade, and modify these sugars are attractive targets for drug development, and also find major use in industrial biotechnology. But carbohydrates are often highly complex and flexible structures, ones that are synthetically challenging, and studying their intimate chemistry has proved difficult. If we are to harness their potential as drug targets, better tools for the study of their interactions with enzymes are required.

    In this Perspective, we review new molecular dynamics simulations using quantum mechanics/molecular mechanics (QM/MM) techniques that have fostered understanding of the mechanisms and conformational dynamics of two important classes of carbohydrate-active enzymes in the past decade. The two classes, glycosyl hydrolases and glycosyltransferases, catalyze the hydrolysis and synthesis, respectively, of glycosidic bonds between carbohydrates and their partner molecules.

    Simulations have revealed the conformational dynamics of distinct reaction pathways taken by different families of glycoside hydrolases and characterized their transition states, findings that will aid inhibitor design. The results have also fueled ongoing debate over which of two proposed mechanisms certain classes of glycosyltransferases follow.  It is shown that QM/MM techniques are now at the forefront of carbohydrate enzymology, providing insights not amenable by other techniques.

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