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 24 publications 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.


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  • Carving at the nanoscale (2011)

    Puntes, Víctor F. (ICN2)

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    Carving at the nanoscale

    What do they have in common a maze, Russian dolls and the ship inside a bottle? The three are objects with internal structure and the three have always fascinated humans. These objects are formed differently: the gardeners sow the walls of the maze, the concentric dolls are modeled separately and assembled later, and the ship enters the bottle with a little string stretches and raises its sails. What never happens is that the sculptor or a gardener enters the initial structure, to model it by carving the final shape from the inside.
    This, not observed at the macroscopic scale, occurs spontaneously at the nanoscale if the ingredients are mixed properly. Nanotechnology allows a solid and compact structure, via chemical processes designed to attack, penetrate and advance digging the initial structure and creating geometric interconnected multi-cavity hollow structures ranging from molecular labyrinths to gold fullerenes, controlled by reaction fronts at the atomic level.
    These capsules protect and carry molecules. If additionally capsules are nanoscaled and inorganic, thanks to its high density of electronic states, they respond to light in resonance and therefore may be open or closed, heated, manipulated by electromagnetic fields such as a cocktail of drugs transported safely to the therapeutic target and drugs administered sequentially on top of pharmacology where the dose is controlled at the cellular level. Last but not least, the synthesis of these structures is performed by controlling processes considered previously undesirable: corrosion! So the recovery of old problems, applied to the nanoscale, results in new exquisite nanostructures.

    If being able to look, touch and manipulate matter at the nanoscale is already amazing, more amazing is that we are able to work inside the nanoparticle. The surface and interior of the nanostructures can be programmed in composition and architecture to make them like a tiny new research laboratory for chemical phenomena, optical, electrical, magnetic, thermal and mechanical stress. For example, it is possible to study quantum confinement phenomena or the coupling of internal and external walls excitations in the presence of electromagnetic radiation, or the study of internal catalytic reactions.

    This work has been developed by Dr. Edgar Gonzalez and Prof. Víctor Puntes at the Catalan Institute of Nanotechnology (ICN), in collaboration with Prof. Jordi Arbiol at the Materials Science Institute of Barcelona (ICMAB-CSIC). And this breakthrough opens a new route for med

  • Fossils of horse teeth indicate "you are what you eat" (2011)

    Rivals, Florent (IPHES)

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    Fossils of horse teeth indicate "you are what you eat"

    Fossil records verify a long-standing theory that horses evolved through natural selection. The records, spanning the past 55 million years, indicate a "critical" lag time between the evolution of horse teeth and dietary changes resulting from climate change.
    While some of the extinct populations examined had extremely abrasive diets, much of the time, it seemed horses had it surprisingly easy. This suggests that "strong natural selection" for different types of teeth only happened occasionally during brief intervals in horse history.
    A methodology known as dental mesowear analysis was used to reconstruct the diets of extinct species by measuring food-related wear and tear on fossil teeth. The data were analysed alongside records of North American climate changes that would have shifted the animals' diets from rainforest fruits and woody, leafy vegetation to the more abrasive diets found in grasslands.
    Lag time in the evolution of horse teeth in comparison to dietary changes is critical. Evolutionary changes in tooth anatomy lag behind the dietary changes by a million years or more.
    While paleontologists have long held horses as classic examples of evolution through natural selection, the theory has been difficult to test because the majority of horse species are extinct. However, the observation that dental changes in horses follow their dietary changes is consistent with evolution due to adaptation.
    The research shows that not only has the number of horse species been greatly reduced in the past few million years, but also that the diets of horses have been narrowly restricted. Living horses are anything but typical examples of the dietary ecology of this once great group of mammals.

  • Long-term projections and acclimatization scenarios of temperature-related mortality in Europe (2011)

    Rodó i López, Xavier (IC3)

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    Long-term projections and acclimatization scenarios of temperature-related mortality in Europe

    The steady increase in greenhouse gas concentrations is inducing a detectable rise in global temperatures. The sensitivity of human societies to warming temperatures is, however, a transcendental question not comprehensively addressed to date. Here we show the link between temperature, humidity and daily numbers of deaths in nearly 200 European regions, which are subsequently used to infer transient projections of mortality under state-of-the-art high-resolution greenhouse gas scenario simulations. Our analyses point to a change in the seasonality of mortality, with maximum monthly incidence progressively shifting from winter to summer. The results also show that the rise in heat-related mortality will start to completely compensate the reduction of deaths from cold during the second half of the century, amounting to an average drop in human lifespan of up 3-4 months in 2070-2100. Nevertheless, projections suggest that human lifespan might indeed increase if a substantial degree of adaptation to warm temperatures takes place.

  • Sweet mysteries of nature: computer simulations unravel how carbohydrates form (2011)

    Rovira Virgili, Carme (PCB)

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    Sweet mysteries of nature: computer simulations unravel how carbohydrates form

    Fifty per cent of our daily calorie intake comes from carbohydrates, our "biological fuel". Moreover, carbohydrates influence cell-to-cell communication, the functioning of the immune system, the ability of various infectious agents to make us sick, and the progression of cancer.

    One of the most important reactions in the metabolism of carbohydrates is the formation of the glycosidic bond, i.e. the covalent linkage between simple monosacharides (monomers) to build polysaccharides such as glucogen, starch or celulose (polymers).

    Most glycosidic bonds are synthesized in nature from sugars that are activated by a cofactor (mostly, a nucleotide). The enzymes responsible for this action are glycosyltransferases (GTs), which form the glycosidic bond by transferring a sugar molecule from a donor molecule (an activated sugar) to an acceptor molecule (typically another sugar). These enzymes can operate with retention or inversion of the configuration of the carbon atom of the glycosidic bond they form. The mechanism of inverting GTs is well known, but the mechanism of retaining GTs has remained one of the most puzzling aspects in the field of glycobiology.

    It had been proposed that the enzyme helps the reaction by binding to the donor molecule. Still, the lack of clear experimental evidence led scientists to think of an extremely unusual "front-face" type mechanism, in which the reaction takes place on a single "face" of the sugar. This mechanism has been surrounded by much controversy, since in principle it implies that two covalent bonds are forming and breaking, respectively, in the same region of space.

    By means of ab initio molecular dynamics techniques and the use supercomputers (BSC), the PCB researchers demonstrated that the "front-face" type mechanism is feasible thanks to the formation of a positively-charged species (a carbocation) with an extremely short half-life that moves quickly from the donor to the acceptor.

    The modelled enzyme is glycosyltransferase trehalose-6-phosphate synthase (OtsA), which participates in the final synthesis of trehalose, a disaccharide of great importance in nature. Given their absence in mammalian biology, trehalose synthesising and processing enzymes offer attractive inhibition targets.

    Glycosyltransferases are responsible for the structure of many carbohydrates and, therefore, the knowledge of their mechanism of action will help to modify their function, thereby improving the synthesis of known carbohydrates and new structures. It will also contribute to th

  • The cell dance: a minuet or a mosh? (2011)

    Trepat, Xavier (IBEC)

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    The cell dance: a minuet or a mosh?

    The physical forces that guide how cells migrate--how they manage to get from place to place in a coordinated fashion inside the living body-- are poorly understood. Our group devised, for the first time, a technique to measure these forces during collective cellular migration. Using this technique we reached the surprising conclusion that the cells fight it out, each pushing and pulling on its neighbors in a chaotic dance, yet together moving cooperatively toward their intended direction.

    Until now it was known that cells could follow gradients of soluble chemical cues, called morphogens, which help to direct tissue development, or they could follow physical cues, such as adhesion to their surroundings. Fundamental studies of these and other mechanisms of cellular migration have focused on dissecting cell behavior into ever smaller increments, trying to get to the molecular roots of how migration occurs. In contrast, we decided to work at a higher level--the group level--and focused on the forces that cells exert upon their immediate neighbors.

    Collective cellular migrations are necessary for multicellular life; for example, in order for cells to form the embryo, cells must move collectively. Or in the healing of a wound, cells must migrate collectively to fill the wound gap. But the migration process is also dangerous in situations such as cancer, when malignant cells, or clumps of cells, can migrate to distant sites to invade other tissues or form new tumors. Understanding how and why collective cellular migration happens may lead to ways to control or interrupt diseases that involve abnormal cell migration. To this aim, we developped a measurement technology called Monolayer Stress Microscopy, which allows us to visualize the nanoscale mechanical forces exerted at the junctions where individual cells are connected.

    We initially thought that as cells are moving--say, to close a wound--the underlying forces would be synchronized and smoothly changing so as to vary coherently across the crowd of cells, as in a minuet. Instead, we found the forces to vary tremendously, occurring in huge peaks and valleys across the monolayer. So the forces are not smooth and orderly at all; they are more like those in a `mosh pit'--organized chaos with pushing and pulling in all directions at once, but collectively giving rise to motion in a given direction. We named this new phenomenon "plithotaxis," a term derived from Greek "plithos" suggestive of throng, swarm or crowd.

  • Antennas for Light (2011)

    van Hulst, Niek F. (ICFO)

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    Antennas for Light

    Antennas are all around in our modern wireless society: they are the front-ends in satellites, cell-phones, laptops, etc., that establish the communication by sending and receiving signals, typically MHz-GHz. Characteristic for any town is the chaotic forest of TV antennas covering roofs: metal bar constructions forming sub-wavelength structures, optimized to receive (or send) directional electro-magnetic fields with the wavelengths of the TV/radio signal. Can the proven antenna technology be scaled up towards the optical domain, i.e. from some 100 MHz towards typically a million times higher frequency of around 500 THz? Inevitably, this implies scaling down to a million times smaller structures, with dimensions of typically 100 nm, requiring nanofabrication accuracy down to a few nm. Moreover metals at optical frequencies are far from ideal, very dispersive and usually lossy. These are definite challenges in scaling antennas towards visible light, but the promise is clear: light, despite its submicron wavelength, is conventionally guided by rather bulky elements, such as lenses, mirrors and optical fibres. Optical antennas convert freely propagating optical radiation into localized energy, and vice versa. They enable the control and manipulation of optical fields at the nanometre scale, comparable to the scale of electronic integrated circuitry, and hold promise for enhancing the performance and efficiency of photodetection, light emission and sensing. Indeed this has motivated the exploration of modern nanofabrication methods, such as focussed electron and ion beams, to fabricate nanostructures and antennas with optical resonances. Although many of the properties and parameters of optical antennas are similar to their radiowave and microwave counterparts, they have important differences resulting from their small size and the resonant properties of metal nanostructures. The review in Nature Photonics, by Lukas Novotny (Inst. Optics, Rochester, USA) and Niek van Hulst (ICFO, Barcelona), describes recent developments in the field, discusses the potential applications and identifies the future challenges and opportunities.