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

  • Designing an enzyme to synthetize carbohydrates via an unusual chemical reaction (2017)

    Rovira Virgili, Carme (UB)

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    Designing an enzyme to synthetize carbohydrates via an unusual chemical reaction

    Sugar or carbohydrate synthesis is important for the development of diagnostic tests, vaccines and new drugs. Conventional chemical synthesis in the laboratory is usually expensive and cumbersome; therefore lots of efforts have been made over the last years to do so with enzymes, which are natural catalysts. However, the enzymes that synthetize sugars (called glycosyltransferases) are hard to express and usually use expensive substrates (nucleotide sugars). Now the teams of the University of Barcelona (C. Rovira) and Oxford (Benjamin G. Davis) have found the way to modify a robust glycosidase enzyme, which normally degrades carbohydrates (by catalyzing the hydrolysis of glycosidic bonds) so that it acts reversely and synthetizes carbohydrates. The modification consisted on a single mutation of one of the catalytic residues. Using properly activated carbohydrate substrates, synthesis instead of hydrolysis was exclusively observed. Moreover, such synthesis takes place with a chemical reaction that had not been observed in glycosidases yet, the so called front-face or SNi-like reaction, which the team of Rovira uncovered in 2011 (see previous Highlight) for glycosyltransferases.

    To prove that the reaction follows a front-face mechanism, Rovira’s team modeled the binding of two carbohydrate molecules in the active site of the engineered enzyme using free energy enhanced sampling methods and modern supercomputers (MareNostrum at BSC-CNS). Afterwards, they obtained the chemical reaction mechanism using quantum mechanics/molecular mechanics (QM/MM) approaches. The computed free energy landscape of the reaction confirmed that the engineered enzyme had changed its catalytic mechanism from SN2 to a SNi type of reaction.

    The advantage of this reaction in glycosidases is that it makes the synthesis in a clean way, without hydrolysis residues and using economically viable substrates (activated sugars). In the study, the synthesis was carried out with a specific enzyme, the Sulfolobus solfataricus β-glycosidase (SSβG), but it can be applied to other enzymes using a similar engineering method, opening new possibilities for carbohydrate biosynthesis.

  • PowerPAD: an eco-friendly battery that eliminates the need of recycling forever (2017)

    Sabaté Vizcarra, Neus (CSIC - IMB-CNM )

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    PowerPAD: an eco-friendly battery that eliminates the need of recycling forever

    This work introduces the PowerPAD battery, the first battery made for portable single-use applications that follows the sustainability guidelines of the circular economy.  The battery is fabricated using exclusively organic materials such as cellulose, carbon, organic redox species and beeswax and does not contain any metals, plastics or harmful substances. In collaboration with researchers from the Simon Fraser University (Vancouver) and the Institut de Recerca I Tecnologia Agroalimentaria (Caldes de Montbui) we showed that their organic composition allows soil microorganisms to literally “eat the batteries” and convert them to CH4 and CO2. Therefore, the batteries can be potentially disposed of in natural soils or already existing compost reactors without any harm and thus eliminate the need for specific recycling. Due to its high cost and energy consumption, battery recycling is a world-wide concern; nowadays less than 30% of sold batteries are collected for proper recycling in developed countries and it is practically inexistent in low resource settings leading to severe contamination of landfills.

    Due to its groundbreaking nature, the idea was initially supported by Melinda and Bill Gates Foundation in 2015 (http://www.electrochem.org/challenge/sabate) and after two years of development it has finally been fulfilled in a prototype that delivers energy for more than 120 minutes and is able to power a portable water sensor. The battery prototype received the Ecodisseny Award from the Generalitat de Catalunya last October as a promising Product of a sustainable future (http://residus.gencat.cat/ca/ambits_dactuacio/sensibilitzacio/premis_med...)

  • New Material Resembling a Metal Nanosponge Could Reduce Computer Energy Consumption to a Minimum (2017)

    Sort Viñas, Jordi (UAB)
    Nogués Sanmiquel, Josep (ICN2)

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    New Material Resembling a Metal Nanosponge Could Reduce Computer Energy Consumption to a Minimum

    In order to store information in the conventional magnetic memories of electronic devices, the materials' small magnetic domains are oriented “up” or “down” by using externally applied magnetic fields. To generate these fields it is necessary to produce electric currents, but these currents heat up materials and a large amount of energy is lost by Joule heating effect. Practically, 40% of the electrical energy used by computers (or “Big Data” servers) is dissipated as heat.

    Prof. Jordi Sort’s Research Team (http://jsort-icrea.uab.cat/) has recently developed a nanoporous material based on a copper-nickel alloy, with a structure similar to that of a sponge, which allows handling and storing magnetic information using very low amount of energy. These nanosponges could be the base of new magnetic memories for computers and mobile phones with enhanced energy efficiency compared to the ones currently in the market.

    The results were recently published and featured in the Advanced Functional Materials journal. The attainment of very small pore sizes, of only 5 - 10 nanometres, together with the very high surface area, were crucial to reduce the energy power consumption. With this vast surface concentrated in a very small space, the Team could apply a small voltage and enormously reduce the energy needed to orient the magnetic domains and record data. This represents a new paradigm for energy saving in computers.

    This research was funded by the ERC-Consolidator Grant received by Professor Jordi Sort for his project SPIN-PORICS (Merging nanoporous materials with energy-efficient spintronics), with a total funding of 1.8M€. To perform the magnetoelectric experiments, and also theoretical modelling, a collaboration was established with the ICN2 Group led by Prof. Josep Nogués.

     

     

  • AN OPTOMECHANICAL LINK BETWEEN CRYPTOGRAPHY AND CHAOS (2017)

    Sotomayor Torres, Clivia Marfa (ICN2)

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    AN OPTOMECHANICAL LINK BETWEEN CRYPTOGRAPHY AND CHAOS

    Cryptography and chaos seem initially unlikely partners. On the one hand, cryptography is based on hidden information requiring certain “order” to be encoded, transmitted, received and decoded. Chaos, on the other hand, conveys the impression of anarchy and loss of control. However, mathematicians would tell us that both concepts involve dynamic processes highly sensitive to initial conditions.

    Complex dynamics are found in optomechanics, which involves the interaction between mechanical modes and light mediated by optical forces. Our experimental model of an optomechanical crystal is a silicon nanobeam patterned by state-of-the-art silicon technology, in such a way that mechanical modes (phonons) overlap in space with optical modes (photons) under confinement conditions.

    Complex dynamics arising from optical non-linearities are observed already in ambient conditions with photons coming from a tuneable laser via a telecommunication optical fibre placed in close proximity to the optomechanical crystal (Fig.1), and the light exiting the fibre captured by a signal analyser. By driving a single optomechanical crystal well into the non-linear regime we show that, as the number of photons stored in the cavity is affected, a chaotic regime is reached which can be smoothly modulated varying the excitation laser parameters. Exploiting the richness of non-linear dynamics we demonstrate accurate control when activating a variety of stable dynamical solutions. The changes in the optical output between the chaotic and coherent regimes are shown in Fig.2.

    Our results have repercussions well beyond our own research in phononic circuits. It could allow information to be coded by introducing chaos in the light that carries it. For example, by linking two integrated chips containing equivalent optomechanical cavities with optical fibers, it would be possible to secure information introducing chaos in the light beam at the emitting point and suppressing it at the reception point.

  • Discovery of protein interactions with long non-coding RNAs (2017)

    Tartaglia, Gian Gaetano (CRG)

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    Discovery of protein interactions with long non-coding RNAs

    Only a small fraction of the human genome (around 2%) contains genes encoding for proteins. The remaining 98% is important for regulation, meaning that it is involved in controlling when and where genes are active. This large portion of the genome produces RNA molecules, called non-coding RNAs, which differ in size, structure and function. As the different types of non-coding RNAs interact with proteins in different ways, big efforts have been put into investigating them. Until now, there were no computational tools available to handle long RNA sequences and studying them through experimental methods is at present a challenge.

    Our new computational tool, catRAPID Global Score, allows us to predict where, along the sequence of a large RNA, a protein will establish a physical contact. To experimentally validate our predictions, we focused on the master regulator of X-chromosome inactivation, Xist.  We unveiled the whole protein network interacting with Xist, which is very relevant to understand how X inactivation plays a key role in dosage compensation mechanisms that allow for equal expression of the X and autosomal chromosomes.

  • Extreme pulsar wind nebula brightening produced by environmental compression (2017)

    Torres, Diego F. (CSIC - ICE)

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    Extreme pulsar wind nebula brightening produced by environmental compression

    Less than a year ago, a pulsar wind nebula generating extended X-ray emission was detected surrounding a magnetar (Swift J1834.9-0846). This was the first magnetar for which such a wind nebula was ever found. The main feature of this magnetar nebula was its large efficiency and size: About 10% of the rotational power of the magnetar was found to be emitted just in X-rays by the nebula, being steady for more than a decade, with a size exceeding 10 light years. This efficiency is about 5 times larger than what is typical for all other nebulae we know in our Galaxy. And magnetars are far from being the most powerful rotators among pulsars...

    How could then a pulsar that dim power a nebula that bright?

    Speculations would soon arise, with suggestions that the nebuale was powered by a yet-unknown mechanism that converts magnetic power into X-rays. But the solution was conceptually simpler:

    By using a detailed radiative and dynamical code that studies the evolution of the nebula and its particle population in time, we find that  Swift J1834.9–0846's nebula (as well as others that could be detected pertaining to its class) can be explained as being rotationally powered, exactly as all other known PWNe are, if it is currently being compressed by the environment. Such compression is called reverberation. Reverberation introduces several new effects, the most important of which is the appearance of adiabatic heating, being increasingly dominant over the escape of particles and any other radiation loss as reverberation goes by. Such heating increases the particle population able to emit X-rays, in a short period of time. This effect is particularly notorious when pulsars are not so powerful, thus its impact on a magnetar nebula is extreme. Particles in a magnetar nebula do not lose, but gain (and gain a lot of) energy, during reverberation.

    Reverberation naturally explains why this is the only magnetar nebula detected up to now (what in itself was a mystery) and provides estimates of Swift 1834.9–0846's age.

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