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NagZThe N-acetylglucosaminidase NagZ of Pseudomonas aeruginosa catalyzes the first cytoplasmic step in recycling of muropeptides, cell-wall-derived natural products. This reaction regulates gene expression for the β-lactam resistance enzyme, β-lactamase. The structural and functional aspects of catalysis by NagZ were investigated by a total of seven X-ray structures, three computational models based on the X-ray structures, molecular-dynamics simulations and mutagenesis. The structural insights came from the unbound state and complexes of NagZ with the substrate, products and a mimetic of the transient oxocarbenium species. The catalytic mechanism involves a histidine as an acid/base catalyst, which is unique in glycosidases and is inhibited by zinc ion. This analysis provides a seamless continuum for the catalytic cycle, incorporating the large motions by loops that surround the active site. This is part of a collaborative effort between the IQFR and the Univ. of Notre Dame (Indiana, USA).

Acebrón, I.; Mahasenan, K.; De Benedetti, S.; Lee, M.; Artola-Recolons, C.; Hesek, D.; Wang, H.; Hermoso*, J.A.; Mobashery*, S. “Catalytic Cycle of the N-Acetylglucosaminidase NagZ from Pseudomonas aeruginosa”. J. Am. Chem. Soc. (2017).
DOI:10.1021/jacs.7b01626

 

LombaCoincident with the anniversary of the demise of our colleague Noé García Almarza, Soft Matter has published one of his last research studies that has also been highlighted in the Inside Front Cover of the aforementioned journal. In this work the self-assembly of spherical particles with three attractive sites distributed symmetrically along the particle equator was investigated under planar confinement. The study of this type of colloidal systems is interesting both from a practical point of view, for the design of new materials with properties 'a la carte', and from a fundamental one, as they often exhibit unusual physical behavior. Indeed, in this article, it is shown that, under certain conditions, these trivalent particles assemble into a rather exotic hybrid solid-gas phase formed by a honey-comb lattice and a gas of particles located at the lattice voids. The concentration of particles at the interstices of the honey-comb lattice varies continuously with pressure without undergoing a true thermodynamic transition, so that at low pressure all the voids are empty, whereas at high pressure all are occupied forming a triangular lattice. The Mechanical Statistics and Condensed Matter group dedicates this work to the memory of our dear friend Noé.

Eva G. Noya, Noé G. Almarza & Enrique Lomba. “Assembly of trivalent particles under confinement: from an exotic solid phase to a liquid phase at low temperature”. Soft Matter 13, 3221 (2017).
DOI:10.1039/C7SM00217C

 

 

sulfatidos enMyelin, the substance that forms the sheaths surrounding the axon of neurons, is an electrical insulator, and therefore is essential for the correct transmission of electrical impulses in the nervous system. The myelin sheath is particularly rich in cholesterol, galactosylceramides and sulfatides. The latter are sulfoglycolipids that can present different unsaturation and hydroxylation degrees. It is known that the nature and ratio of the different sulfatide molecular species change with age. They have also been associated with the pathogenesis of various diseases of the human Central Nervous System, including multiple sclerosis, Parkinson’s disease, leukodystrophy and Alzheimer’s disease. Consequently, these molecules could potentially be used as biomarkers of neurological diseases. However, the identification and quantification of sulfatides is a very difficult task due to their low concentrations and the high number of different molecular species. This is the reason why most of the studies only analyse the main sulfatides.
The use of liquid chromatography coupled to high-resolution tandem mass spectrometry with electrospray ionisation (LC-ESI(+)-MS/MS) has allowed us to develop an analytical method capable of carrying out a reliable identification and quantification of 37 sulfatides, many of them not detected so far. These results can be very useful in bioanalysis, due to the capability of correctly identifying these potential markers, even at concentrations of nanograms per millilitre.
This work has been possible thanks to the collaboration of researchers from IQFR, IQOG, ICTP and Cajal Institute, all of CSIC.

M. Pintado-Sierra, I. García-Álvarez, A. Bribián, E.M. Medina-Rodríguez, R. Lebrón-Aguilar, L. Garrido, F. de Castro, A. Fernández-Mayoralas, J.E. Quintanilla-López. “A comprehensive profiling of sulfatides in myelin from mouse brain using liquid chromatography coupled to high-resolution accurate tandem mass spectrometry” Anal. Chim. Acta, (2017) 951, 89-98.
DOI: 10.1016/j.aca.2016.11.054

 

oxidantesOzone (O3) and hydroxyl (OH) and nitrate (NO3) radicals are the main atmospheric components that oxidize organic and inorganic pollutants, therefore affecting air quality, environmental health and climate. Measurements from the air quality monitoring network in Madrid show an increase in ozone levels of 30-40% from 2007 to 2014, while nitrogen dioxide (NO2) has dropped by 20-40%. Based on these measurements and a high spatial resolution air quality model, we estimate an average increase of 10% and 32% in OH and NO3, respectively, in Madrid, with increases of up to 70% and 90%, respectively, downtown. Our results also show a reduction of 11% in nitric acid (HNO3), which implies a considerable denoxification of the urban atmosphere and decrease of the minus 2.5 micrometre particle (PM2.5) levels. These results suggest that current NOx (NO + NO2) emission reduction policies lead to significant changes in the chemistry and the oxidative capacity of the atmosphere in and around large cities. The image shows the modelled change in OH levels between 2007 and 2014. These results have been published in Scientific Reports.

A. Saiz-Lopez, R. Borge, A. Notario, J. A. Adame, D. de la Paz, X. Querol, B. Artíñano, F. J. Gómez-Moreno & C. A. Cuevas. “Unexpected increase in the oxidation capacity of the urban atmosphere of Madrid, Spain”. Sci. Rep. (2017) 7, 45956.
DOI: 10.1038/srep45956

 

historia contaminacionWe have reconstructed the mercury and lead atmospheric deposition in NE Spain during the last 700 years using the concentration of these pollutants in lake sediments from the Pyrenees (Lake Montcortès). The main source of atmospheric mercury deposited in the lake is related to the mercury production in Almadén (the world´s largest mercury mine). Lead pollution is related to local mining activities in the Pyrenees and the use of leaded gasoline during the second half of the 20th century. This study highlights the sensitiveness of lake sediments to atmospheric pollution from a historical perspective.
The attached figure (linked to a bigger one) shows the Mercury (Hg) and lead (Pb) deposition rates since the 14th century, and their relationship to i) mercury production in Almadén, ii) local galena mining in the Pyrenees, and iii) the period using leaded gasoline in Europe (between 1950 and 1990).
Corella, J.P., Valero-Garcés, B.L., Wang, F., Martínez-Cortizas, A., Cuevas, C.A., Saiz-Lopez, A. “700 years reconstruction of mercury and lead atmospheric deposition in the Pyrenees (NE Spain)”. Atmospheric Environment (2017) 155, 97-107. (doi: 10.1016/j.atmosenv.2017.02.018)

 

 

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