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
  • Solving protein structures using genetics (2019)

    Lehner, Ben (CRG)

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    Solving protein structures using genetics

    Determining the three-dimensional structures of macromolecules is a major goal of biological research because of the close relationship between structure and function.   Structure determination usually relies on physical techniques including X-ray crystallography, NMR spectroscopy and cryo-electron microscopy. We have developed an alternative method that allows the high-resolution three-dimensional backbone structure of a biological macromolecule to be determined only from measurements of the activity of mutant variants of the molecule. This genetic approach to structure determination relies on the quantification of genetic interactions (epistasis) between mutations and the discrimination of direct from indirect interactions. This provides an alternative experimental strategy for structure determination and one that allows the power of high throughput genomics to be applied to structural biology. It also allows the structures of molecules to be determined as they are performing their functions inside cells.

  • Multicolored light twists in new knotted ways (2019)

    Lewenstein, Maciej Andrzej (ICFO)

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    Multicolored light twists in new knotted ways

    Around age six, we start learning how to tie our shoelaces, making knots that look like ribbons — or possibly more complex forms, if we are a little clumsy. We use knots every day, but the type of knots we generally use is associated with physical objects, things we can touch. In a recent study, published in two papers, joint collaborations by ICREA/ICFO researchers demonstrated multicolored light twists in new knotted ways. They have broken theoretical and experimental ground in this new field, uncovering new types of knots for twisted light and a new type of angular momentum.

    In the first paper, published in Nature Photonics, ICFO researchers Emilio Pisanty, Gerard Jiménez Machado, Veronica Vicuña-Hernández, Antonio Picón, and Alessio Celi, led by ICREA Prof. at ICFO Maciej Lewenstein and UPC Prof. at ICFO Juan P. Torres, have designed a beam of light with a polarization state that forms three-lobed trefoils at each point, by combining light of different frequencies, and making the trefoils connect to each other in a way such that the light beam, as a whole, has the shape of a knot. These beams also exhibit a new kind of angular momentum, associated with the unusual symmetry of the beams, which remain unchanged when they’re rotated — but only when the polarization is rotated by a specific portion of the rotation in space. This new quantity is termed the torus-knot angular momentum, because of the type of knot in the beams, and the researchers were able to experimentally confirm its presence.

    In the second paper, published in Physical Review Letters, ICFO researchers Emilio Pisanty and Antonio Picón, led by ICREA Professor at ICFO Maciej Lewenstein, in collaboration with researchers from the University of Salamanca and from CU Boulder, show that the new type of angular momentum is conserved in interactions. They show, via theoretical simulations, that at extremely high intensities, many photons of light can be combined into single photons with high energy, and that these new, bigger photons carry the combined torus-knot angular momentum of the original, smaller photons.

  • The Mutational Footprints of Cancer Therapies (2019)

    López-Bigas, Núria (IRB Barcelona)

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    The Mutational Footprints of Cancer Therapies

    As we age our cells accumulate mutations due to a number of different processes.  The source of these mutations can be exogenous (e.g., solar radiation, tobacco smoke or some toxic substance) or endogenous (e.g., errors in DNA copying). Each of these mutational processes leave a specific footprint in the DNA, which we call its mutational signature or footprint.

    Since many cancer treatments affect DNA, we reasoned that they may leave a specific mutational footprint in the DNA of the cells of treated patients.

    We analyzed the mutations identified in the genomes of more than 3500 metastases of formerly treated patients and using ad hoc bioinformatic analyses, we identified the mutational footprints of six therapies widely used for the treatment of cancer (five based on drugs used as chemotherapies, and radiotherapy).

    Using these footprints, we then can quantified the mutations likely caused by each kind of chemotherapy. We expect that these findings will allow for precise assessment of the mutational risk of different cancer therapies to understand their long-term side effects.

     

  • New physics effects in fusion plasmas revealed by three-dimensional computations   (2019)

    Mantsinen, Mervi Johanna (BSC-CNS)

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    New physics effects in fusion plasmas revealed by three-dimensional computations  

    Shear Alfvén instabilities are of considerable interest in fusion plasma research. These instabilities can be driven by energetic particles such as fusion products. Not only can the Alfvén instabilities degrade the confinement and heating efficiency of energetic particles by channeling them but they can also cause severe damage to the plasma-facing components of the plasma confining vessel through high heat fluxes. Thus, investigations of their control, better performance and comprehensive understanding are required.

    We have carried out detailed modelling and analysis of experimentally observed energetic particle-driven Alfvénic instabilities in tokamak and stellarator plasmas using three dimensional (3D) numerical tools based on the reduced magnetohydrodynamics (MHD) model.

    To explain experimental observations of Alfvén instabilities in TJ-II flexible heliac plasmas, we have compared experimental results with the results obtained through theoretical model of shear Alfvén waves in a 3D toroidal geometry and obtained qualitative agreement.

    We have also modelled bifurcated MHD equilibria with 3D helical core surrounded by an axisymmetric 2D mantle for the ASDEX Upgrade tokamak plasmas and compared them to an axisymmetrical 2D case (cf. figure). Our modelling results reveal interesting new physics effects due to 3D helical core such as continuum splitting and variation of mode frequency around the frequency accumulation point as well as new frequency gaps due to helical distortion.

  • Research on HIV/AIDS enables new treatments for Ebola virus (2019)

    Martínez-Picado, Javier (IrsiCaixa)

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    Research on HIV/AIDS enables new treatments for Ebola virus

    Dendritic cells are the most potent antigen presenting cells found in humans and their immune function is key to initiate immunity against invading viruses. These cellular sentinels patrol distinct mucosae and upon infection, viral sensing triggers rapid innate immune responses that might initially contain viral spread. Activation of dendritic cells subsequently elicits their cellular migration towards lymphoid tissues, where they trigger a more selective immune response against the assaulting pathogens.

    In 2012, while working on immune pathogenic mechanisms involving HIV-1 –the AIDS virus–, the retrovirology team at the IrsiCaixa AIDS Research Institute described a new interaction between specific glycolipids (dubbed gangliosides) in the viral membrane and the protein Siglec-1 (or CD169) on the dendritic cell membrane. The characterization of this new ligand-receptor interaction opened a wide range of translational possibilities, not only including HIV-1 control, but also other enveloped viruses.

    Filoviruses, such as Ebola virus, cause a severe fever having a very high case fatality rate. Since 1976 several Ebola viruses cause outbreaks in humans. The largest one ever recorded occurred in West-Africa between 2014-2016, with 28,646 infected patients and 11,323 reported deaths. At that time, the research group was investigating other potential ganglioside-containing viruses that could exploit Siglec-1 as an attachment receptor in myeloid cells, which are in vivo targets of filoviruses. They have now found that Ebola virus-like particles also bind to Siglec-1 on activated dendritic cells upon recognition of their gangliosides.

    This observation opens the door to develop pan-viral inhibitors based on this mechanism of action. The team has generated a series of monoclonal antibodies that specifically bind to Siglec-1. Blockage of the Siglec-1 receptor by anti-Siglec-1 antibodies halts Ebola viral uptake and cytoplasmic entry, offering cross-protection against other ganglioside-containing viruses such as HIV-1. As a result, two patents have been filed to protect these antibodies as potential therapeutic agents.

  • Color Superconductivity, Neutron Stars and Holography  (2019)

    Mateos, David (UB)

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    Color Superconductivity, Neutron Stars and Holography 

    Under ordinary conditions quarks and gluons are confined inside the protons and neutrons contained in the atoms that make us and the things around us. However, quarks and gluons may form a completely different type of matter at the core of neutron stars, where the strong gravitational force compresses them to the highest densities known in Nature. It is conjectured that one such phase may be a "color superconductor". This is an analog of the ordinary electromagnetic superconductors that are used, for example, to make trains levitate. The key difference is that, in a color superconductor, the electromagnetic force is replaced by the strong nuclear force. Color superconductors might be discovered experimentally via the gravitational wave signals emitted in neutron star mergers like the one first detected in August 2017. 

    The presence of the strong nuclear force makes the theoretical description of color superconductors by conventional methods extremely difficult. For this reason we have used a string-theoretical tool known as “holography”, which maps the properties of matter in our four-dimensional world to those of … string theory in ten dimensions!

    We have shown that, in the string theory description, the properties of the color superconductor are encoded in the bending in the extra dimensions of higher-dimensional objects known as "D-branes", as shown in the figure. This geometrization of the problem provides a completely new (and higher-dimensional) perspective on color superconductors. As usual in physics, such a new viewpoint brings with it a new level of understanding that we are just beginning to unravel.