Improvement on binding of chondroitin sulfate derivatives to midkine by increasing hydrophobicity

The interactions between chondroitin sulfate (CS) and a wide number of proteins modulate important biological processes. Here, the binding properties to midkine and pleiotrophin of sulfated, fully protected intermediates, typically obtained in the chemical synthesis of CS oligosaccharides, were tested for the first time. Using a fluorescence polarization competition experiment, we discovered that these synthetic precursors strongly bound these two closely related cytokines involved in cancer and inflammation. The relative binding affinities of these intermediates were significantly higher than those displayed by the corresponding fully deprotected oligosaccharides, indicating that the presence of hydrophobic protecting groups strongly enhanced the binding of CS-like derivatives to midkine. These compounds offer novel opportunities for the development of potent inhibitors/activators of CS-protein interactions with potential therapeutic applications.Ministerio de Economía y Competitividad CTQ2012-3260

Synthesis of (1→3) Thiodisaccharides of GlcNAc and the Serendipitous Formation of 2,3-Dideoxy-(1→2)-thiodisaccharides through a Vinyl Azide Intermediate

The syntheses of β-S-GlcA(1→3)GlcNAc and β-S-Gal(1→3)GlcNAc thiodisaccharides, which can be considered mimetics of the repeating units of hyaluronan and keratan respectively, were achieved by SN2 displacement of a triflate group allocated at the 3-position of a convenient 2- azido-4,6-O-benzylidene-2-deoxy-β-D-allopyranose precursor by the corresponding nucleophilic suitable protected thioaldoses derived from glucuronic acid (GlcA) and galactose (Gal). The study of the reaction led to the finding that the vinyl azide formed by competitive E2 reaction of the mentioned triflate was an interesting precursor of a new kind of 2,3-dideoxy-2-azido-(1→2) thiodisaccharides through an addition reaction. Determination of the stereochemistry of the new stereocenter at C-2 was achieved by NOESY experiments. Final protecting group manipulation of the (1→3) thiodisaccharides led to a family of derivatives that could be used as building blocks for the synthesis of complex glycomimetics.Fil: Cristófalo, Alejandro Ezequiel. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; ArgentinaFil: Nieto, Pedro M.. Universidad de Sevilla; España. Consejo Superior de Investigaciones Científicas; EspañaFil: Uhrig, Maria Laura. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; Argentin

Catalytic hydrodechlorination as polishing step in drinking water treatment for the removal of chlorinated micropollutants

This Accepted Manuscript will be available for reuse under a CC BY-NC-ND license after 24 months of embargo periodThe presence of micropollutants in fresh waters represents an important challenge for drinking water treatment plants (DWTPs). In particular, the chlorinated ones are especially harmful given their high toxicity and strong bioaccumulation potential. The aim of this work is to evaluate the feasibility of catalytic hydrodechlorination (HDC) for the removal of a representative group of chlorinated micropollutants commonly found in the source waters of DWTPs: the antibiotic chloramphenicol (CAP), the anti-inflammatory diclofenac (DCF), the antibacterial agent triclosan (TCL) and the antidepressant sertraline (SRT). The complete degradation of the isolated micropollutants (3 mg L−1) was achieved in 1 h reaction time using a Pd/Al2O3 catalyst load of 0.25 g L−1 and a H2 flow rate of 50 N mL min−1. The experimental data were properly described by a pseudo-first order kinetic equation, obtaining degradation rate constants in the range of 0.32–1.56 L gcat−1 min−1 and activation energy values within 42–52 kJ mol−1. In all cases, the final reaction products were chlorine-free compounds and thus, HDC effluents were non-toxic (<0.1 TU). Remarkably, the catalyst showed a suitable stability upon five consecutive applications. The versatility of the process was demonstrated in the treatment of the micropollutants mixture in different aqueous matrices (mineral, surface and tap waters). Strikingly, the removal rate was not affected by the presence of co-existing substances, being the micropollutants completely removed in 15 min with 1 g L−1 catalyst concentration. Finally, the potential of HDC for the removal of trihalomethanes, by-products formed along the oxidation step by chlorination in DWTPs, was also demonstratedThis research has been supported by the Spanish MINECO thorough the project CTM2016-76454-R and by the CM through the project P2018/EMT-4341. J. Nieto-Sandoval thanks the Spanish MINECO for the FPI predoctoral grant (BES-2017- 081346). M. Munoz thanks the Spanish MINECO for the Ramón y Cajal postdoctoral contract (RYC-2016-20648

Langerin-Heparin Interaction: Two Binding Sites for Small and Large Ligands as revealed by a combination of NMR Spectroscopy and Cross-Linking Mapping Experiments

Langerin is a C-type lectin present on Langerhans cells that mediates capture of pathogens in a carbohydrate-dependent manner, leading to subsequent internalization and elimination in the cellular organelles called Birbeck granules. This mechanism mediated by langerin was shown to constitute a natural barrier for HIV-1 particle transmission. Besides interacting specifically with high mannose and fucosylated neutral carbohydrate structures, langerin has the ability to bind sulfated carbohydrate ligands as 6-sulfated galactosides in the Ca2+ dependent binding site. Very recently langerin was demonstrated to interact with sulfated glycosaminoglycans (GAGs), in a Ca2+ independent way, resulting in the proposal of a new binding site for GAGs. Based on those results, we have conducted a structural study of the interactions of small heparin (HEP) like oligosaccharides with langerin in solution. Heparin-bead cross-linking experiments, an approach specifically designed to identify HEP/HS binding sites in proteins were first carried out and experimentally validated the previously proposed model for the interaction of Lg ECD with 6 kDa HEP. High-resolution NMR studies of a set of 8 synthetic HEP-like trisaccharides harboring different sulfation patterns demonstrated that all of them bound to langerin in a Ca2+ dependent way. The binding epitopes were determined by STD NMR and the bound conformations by transferred NOESY experiments. These experimental data were combined with docking and molecular dynamics and resulted in the proposal of a binding mode characterized by the coordination of calcium by the two equatorial hydroxyl groups OH3 and OH4 at the non-reducing end. The binding also includes the carboxylate group at the adjacent iduronate residue. Such epitope is shared by all the 8 ligands, explaining the absence of any impact on binding from their differences in substitution pattern. Finally, in contrast to the small trisaccharides, we demonstrated that a longer HEP-like hexasaccharide, bearing an additional O-sulfate group at the non-reducing end, which precludes binding to the Ca2+ site, interacts with langerin in the previously identified Ca2+ independent binding site

Adsorption of micropollutants onto realistic microplastics: role of microplastic nature, size, age, and NOM fouling

This work aims at evaluating the role of nature, size, age, and natural organic matter (NOM) fouling of realistic microplastics (MPs) on the adsorption of two persistent micropollutants (diclofenac (DCF) and metronidazole (MNZ)). For such goal, four representative polymer types (polystyrene (PS), polyethylene terephthalate (PET), polypropylene (PP) and high-density polyethylene (HDPE)) were tested. MPs were obtained by cryogenic milling of different commercial materials (disposable bottles, containers, and trays), and fully characterized (optical microscopic and SEM images, FTIR, elemental analysis, water contact angle and pHslurry). The micropollutants hydrophobicity determined to a high extent their removal yield from water. Regardless of the MP's nature, the adsorption capacity for DCF was considerably higher than the achieved for MNZ, which can be related to its stronger hydrophobic properties and aromatic character. In fact, aromatic MPs (PS and PET) showed the highest adsorption capacity values with DCF (~100 μg g−1). The MP size also played a key role on its adsorption capacity, which was found to increase with decreasing the particle size (20–1000 μm). MPs aging (simulated by Fenton oxidation) led also to substantial changes on their sorption behavior. Oxidized MPs exhibited acidic surface properties which led to a strong decrease on the adsorption of the hydrophobic micropollutant (DCF) but to an increase with the hydrophilic one (MNZ). NOM fouling (WWTP effluent, river water, humic acid solution) led to a dramatic decrease on the MPs sorption capacity due to sorption sites blocking. Finally, the increase of pH or salinity of the aqueous medium increased the micropollutants desorptionThis research has been supported by the Autonoma University of Madrid and Community of Madrid through the project SI1-PJI-2019-00006, and by the Spanish MINECO through the project PID2019-105079RB-I00. Muñoz and J. Nieto-Sandoval thank the Spanish MINECO for the Ramón y Cajal postdoctoral contract (RYC-2016-20648) and the FPI predoctoral grant (BES-2017-081346), respectively. D. Ortiz thanks the Spanish MIU for the FPU predoctoral grant (FPU19/04816

A Hybrid Parameterization Technique for Speaker Identification

Classical parameterization techniques for Speaker Identification use the codification of the power spectral density of raw speech, not discriminating between articulatory features produced by vocal tract dynamics (acoustic-phonetics) from glottal source biometry. Through the present paper a study is conducted to separate voicing fragments of speech into vocal and glottal components, dominated respectively by the vocal tract transfer function estimated adaptively to track the acoustic-phonetic sequence of the message, and by the glottal characteristics of the speaker and the phonation gesture. The separation methodology is based in Joint Process Estimation under the un-correlation hypothesis between vocal and glottal spectral distributions. Its application on voiced speech is presented in the time and frequency domains. The parameterization methodology is also described. Speaker Identification experiments conducted on 245 speakers are shown comparing different parameterization strategies. The results confirm the better performance of decoupled parameterization compared against approaches based on plain speech parameterization

Chondroitin Sulfate Tetrasaccharides: Synthesis, Three-Dimensional Structure and Interaction with Midkine

The biological activity of midkine, a cytokine implicated in neuro- and tumourigenesis, is regulated by its binding to glycosaminoglycans (GAGs), such as heparin and chondroitin sulfate (CS). To better understand the molecular recognition of GAG sequences by this growth factor, the interactions between synthetic chondroitin sulfate-like tetrasaccharides and midkine were studied by using different techniques. Firstly, a synthetic approach for the preparation of CS-like oligosaccharides in the sequence GalNAc-GlcA was developed. A fluorescence polarisation competition assay was then employed to analyse the relative binding affinities of the synthetic compounds and revealed that midkine interacted with CS-like tetrasaccharides in the micromolar range. The 3D structure of these tetramers was studied in detail by a combination of NMR spectroscopy experiments and molecular dynamics simulations. Saturation transfer difference (STD) NMR spectroscopy experiments indicate that the CS tetrasaccharides bind to midkine in an extended conformation, with similar saturation effects along the entire sugar chain. These results are compatible with docking studies that suggest an interaction of the tetrasaccharide with midkine in a folded structure. Overall, this study provides valuable information on the interaction between midkine and well-defined, chemically synthesised CS oligosaccharides and these data can be useful for the design of more active compounds that modulate the biological function of this protein.Peer Reviewe

Degradation of widespread cyanotoxins with high impact in drinking water (microcystins, cylindrospermopsin, anatoxin-a and saxitoxin) by CWPO

This Accepted Manuscript will be available for reuse under a CC BY-NC-ND license after 24 months of embargo periodThe occurrence of harmful cyanobacterial blooms has unabated increased over the last few decades, posing a significant risk for public health. In this work, we investigate the feasibility of catalytic wet peroxide oxidation (CWPO) promoted by modified natural magnetite (Fe3O4-R400/H2O2), as an inexpensive, simple-operation and environmentally-friendly process for the removal of the cyanotoxins that show the major impact on drinking water: microcystins (MC-LR and MC-RR), cylindrospermopsin (CYN), anatoxin-a (ATX) and saxitoxin (STX). The performance of the system was evaluated under ambient conditions and circumneutral pH (pH0 = 5) using relevant cyanotoxin concentrations (100–500 μg L−1). The nature of the cyanotoxins determined their reactivity towards CWPO, which decreased in the following order: MC-RR > CYN > MC-LR ≫ ATX > STX. In this sense, microcystins and CYN were completely removed in short reaction times (1–1.5 h) with a low catalyst concentration (0.2 g L−1) and the stoichiometric amount of H2O2 (2–2.6 mg L−1), while only 60–80% conversion was achieved with ATX and STX in 5 h. In these cases, an intensification of the operating conditions (1 g L−1 catalyst and up to 30 mg H2O2 L−1) was required to remove both toxins in 1 h. The impact of the main components of freshwaters i.e. natural organic matter (NOM) and several inorganic ions (HCO3−, HPO42-, SO42-) on the performance of the process was also investigated. Although the former led to a partial inhibition of the reaction due to HO· scavenging and catalyst coating, the latter did not show any remarkably effect, and the versatility of the process was finally confirmed in a real surface water. To further demonstrate the effectiveness of the catalytic system, the toxicity of both the initial cyanotoxins and the resulting CWPO effluents was measured with the brine shrimp Artemia salina. Remarkably, all CWPO effluents were non-toxic at the end of the treatment.This research has been supported by the Spanish MINECO through the project CTM-2016-76454-R and by the CM through the project P2018/EMT-4341. M. Munoz thanks the Spanish MINECO for the Ramón y Cajal postdoctoral contract (RYC-2016-20648). J. Nieto-Sandoval thanks the Spanish MINECO for the FPI predoctoral grant (BES-2017-081346

Tracking magmatism and oceanic change through the early Aptian Anoxic Event (OAE 1a) to the late Aptian: Insights from osmium isotopes from the westernmost Tethys (SE Spain) Cau Core

Some of the major Carbon cycle perturbations of the Phanerozoic occurred during the Aptian, in relation to magmatism. The highest temperatures reconstructed for the Cretaceous Period correspond to the Oceanic Anoxic Event of the early Aptian (OAE 1a), an episode of accelerated global change. Here we present a chemostratigraphic study based on osmium isotopes integrated with high-resolution Carbon-Oxygen stable isotope data from the Cau Core (Western Tethys, SE Spain), including a 6.4 Ma record from the early to the late Aptian. This high-resolution study of the continuous and expanded Cau section permits a thorough understanding of the duration of the Aptian events, as well as an evaluation of the mechanisms triggering the abrupt changes of the global carbon and osmium cycles and their interdependence. Here we show that the Large Igneous Province (LIP) Aptian magmatism initiated 550–750 kyr prior to the OAE 1a, and persisted for 1.4 Myr after the event, influencing the composition of seawater for 2.8 Myr. We show a continuous Os isotope record encompassing the OAE 1a and the late Aptian for the first time, and demonstrate that the recovery from the exceptionally unradiogenic composition of seawater Os produced by the dominance of the Ontong Java Plateau volcanism, was slow. Our results demonstrate the different time duration of some events, and the asynchronous relationship between the carbon and osmium cycles

Insights on the removal of the azole pesticides included in the EU Watch List by Catalytic Wet Peroxide Oxidation

The aim of this work is to evaluate the feasibility of the Catalytic Wet Peroxide Oxidation (CWPO) process using the inexpensive and environmentally friendly Fe3O4-R400 catalyst for the removal from water of a representative group of azole pesticides recently listed in the European Union (EU) Watch Lists (penconazole (PEN), prochloraz (PCZ), tebuconazole (TEB), tetraconazole (TET), metconazole (MET)). The complete removal of these pollutants (1000 μg L−1) was achieved in <1 h reaction time under ambient conditions using a catalyst concentration of 0.5 g L−1 and the stoichiometric dose of H2O2 (3 – 5 mg L−1) at a slightly acidic pH (pH0 = 5.0). To further demonstrate the effectiveness of the process, the ecotoxicity abatement was also considered. The initial toxicity of the pesticides and the CWPO effluents were evaluated with the brine shrimp Artemia salina and the bacterium Vibrio fischeri. Remarkably, the effluents were non-toxic for V. fischeri and a decrease of more than 80% in mortality was achieved for A. salina. Furthermore, the versatility of the system was proved in real water matrices (surface water and WWTP effluent), although a slight decrease on the oxidation rate was found due to the occurrence of organic matter and inorganic salts. The reactivity of the azole pesticides was finally compared with the achieved for other groups of pollutants included in the EU Watch Lists (pharmaceuticals, hormones, and neonicotinoid pesticides). Clearly, azole compounds showed the least reactivity to oxidation, suggesting that they can be used as general indicators of the overall efficiency of the proposed catalytic system for the removal of EU Watch Lists micropollutantsThis research has been supported by the Spanish AEI through the project PID2019-105079RB-100 and by the CM, Spain through the project P2018/EMT-4341. M. Munoz, N. Lopez-Arago and J. Nieto-Sandoval thanks the Spanish AEI for the Ramón y Cajal postdoctoral contract (RYC-2016-20648), the FPI predoctoral, Spain grant (PRE2020-09452) and the FPI postdoctoral, Spain grant (BES-2017-081346), respectivel