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[EN] A rationalized design of the organic structure directing agents (OSDAs) allows the preparation of zeolites with specific framework topologies, crystal sizes and/or chemical compositions. In the last years, organic molecules containing aromatic rings in their structures have been described as efficient OSDAs for the synthesis of zeolites with different physico-chemical properties. The unique ability of these aromatic molecules to form rigid and bulky OSDAs by supramolecular self-assembling of two organic molecules, mainly through p–p interactions, has allowed the synthesis of zeolites with large void volumes, controlled chemical distribution and/or high external surface areas. Along the present review, I would like to highlight the recent achievements reported in the literature using aromatic self-assembled bulky dimers as OSDAs for the synthesis of zeolites., Financial support by the Spanish Government-MINECO through "Severo Ochoa" (SEV 2012-0267), Consolider Ingenio 2010-Multicat, MAT2012-37160 and, Intramural-201480I015 is acknowledged. The author especially acknowledges to Dr. Cristina Martinez and Prof. Avelino Corma for helpful discussions.

In amyotrophic lateral sclerosis (ALS), an adult onset disease in which there is progressive degeneration of motoneurones, it has been suggested that an intrinsic hyperexcitability of motoneurones (i.e. an increase in their firing rates), contributes to excitotoxicity and to disease onset. Here we show that there is no such intrinsic hyperexcitability in spinal motoneurones. Our studies were carried out in an adult mouse model of ALS with a mutated form of superoxide dismutase 1 around the time of the first muscle fibre denervations. We showed that the recruitment current, the voltage threshold for spiking and the frequency-intensity gain in the primary range are all unchanged in most spinal motoneurones, despite an increased input conductance. On its own, increased input conductance would decrease excitability, but the homeostasis for excitability is maintained due to an upregulation of a depolarizing current that is activated just below the spiking threshold. However, this homeostasis failed in a substantial fraction of motoneurones, which became hypoexcitable and unable to produce sustained firing in response to ramps of current. We found similar results both in lumbar motoneurones recorded in anaesthetized mice, and in sacrocaudal motoneurones recorded in vitro, indicating that the lack of hyperexcitability is not caused by anaesthetics. Our results suggest that, if excitotoxicity is indeed a mechanism leading to degeneration in ALS, it is not caused by the intrinsic electrical properties of motoneurones but by extrinsic factors such as excessive synaptic excitation.

Titanosilicate forms of expanded MWW-related material are synthesized starting from a pure silica precursor, ITQ-1. This procedure improves the current synthetic route of the expanded titanosilicate MWW material (Ti-YNU-1), which requires the use of a borosilicate MWW as precursor and, consequently, several postsynthetic acid treatments for removing boron atoms from the framework. The expanded Ti-MWW-related materials presented here show better activity than regular Ti-MWW in the selective epoxidation reaction of cyclohexene using H2O2 as oxidant., Financial support by the Spanish MINECO (MAT2012-37160, and Consolider Ingenio 2010-Multicat), Generalitat Valenciana by the PROMETEO program, and UPV through PAID-06-11 (no. 1952) is acknowledged. M.M. also acknowledges "Subprograma Ramon y Cajal" for the contract RYC-2011-08972.

[EN] Isomerization of sugars is used in a variety of industrially relevant processes and in glycolysis. Here, we show that hydrophobic zeolite beta with framework tin or titanium Lewis acid centers isomerizes sugars, e.g., glucose, via reaction pathways that are analogous to those of metalloenzymes. Specifically, experimental and theoretical investigations reveal that glucose partitions into the zeolite in the pyranose form, ring opens to the acyclic form in the presence of the Lewis acid center, isomerizes into the acyclic form of fructose, and finally ring closes to yield the furanose product. The zeolite catalysts provide processing advantages over metalloenzymes such as an ability to work at higher temperatures and in acidic conditions that allow for the isomerization reaction to be coupled with other important conversions., The work at Caltech and the University of Delaware was financially supported as part of the Catalysis Center for Energy Innovation, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award DE-SC0001004. M.M acknowledges the Fundacion Ramon Areces Postdoctoral Research Fellowship Program and the "Subprograma Ramon y Cajal" for Contract RYC-2011-08972 for financial support. R.B.D. acknowledges the Obra Social "la Caixa" for a graduate fellowship. A.P. acknowledges the Caltech Summer Undergraduate Research Fellowship program(SURF) for financial support. The computational studies for this work were supported by the U.S. Department of Energy under Contract DE-AC0206CH11357 and this material is based upon work supported as part of the Institute for Atom-efficient Chemical Transformations (IACT), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences. We gratefully acknowledge grants of computer time from the ANL Laboratory Computing Resource Center (LCRC), and the ANL Center for Nanoscale Materials. This research used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Sciences of the U.S. Department of Energy under Contract DE-AC02-05CH11231.

Classical studies of the mammalian neuromuscular system have shown an impressive adaptation match between the intrinsic properties of motoneurons and the contractile properties of their motor units. In these studies, the rate at which motoneurons start to fire repetitively corresponds to the rate at which individual twitches start to sum, and the firing rate increases linearly with the amount of excitation (“primary range”) up to the point where the motor unit develops its maximal force. This allows for the gradation of the force produced by a motor unit by rate modulation. In adult mouse motoneurons, however, we recently described a regime of firing (“subprimary range”) that appears at lower excitation than what is required for the primary range, a finding that might challenge the classical conception. To investigate the force production of mouse motor units, we simultaneously recorded, for the first time, the motoneuron discharge elicited by intracellular ramps of current and the force developed by its motor unit. We showed that the motor unit developed nearly its maximal force during the subprimary range. This was found to be the case regardless of the input resistance of the motoneuron, the contraction speed, or the tetanic force of the motor unit. Our work suggests that force modulation in small mammals mainly relies on the number of motor units that are recruited rather than on rate modulation of individual motor units.

Does the afterhyperpolarization current control the gain and discharge variability of motoneurones according to the same law? We investigated this issue in lumbar motoneurones of anaesthetized cats. Using dynamic clamp, we measured the conductance, time constant and driving force of the AHP current in a sample of motoneurones and studied how the gain was correlated to these quantities. To study the action of the AHP on the discharge variability and to compare it to its action on the gain, we injected an artificial AHP-like current in motoneurones. This increased the natural AHP. In three motoneurones, we abolished most of the natural AHP with the calcium chelator BAPTA to investigate the condition where the discharge was essentially controlled by the artificial AHP. Our results demonstrate that both the gain and the coefficient of variation of the firing rate are inversely proportional to the magnitude and to the time constant of the artificial AHP conductance. This indicates that the AHP exerts the same control over the gain and the variability. This mechanism ensures that the variability of the discharge is modulated with the gain. This guarantees a great regularity of the discharge when the motoneurone is in a low excitability state and hence good control of the force produced.