Martian dust storm impact on atmospheric H2O and D/H observed by ExoMars Trace Gas Orbiter.

Global dust storms on Mars are rare1,2 but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere3, primarily owing to solar heating of the dust3. In turn, changes in atmospheric dynamics can affect the distribution of atmospheric water vapour, with potential implications for the atmospheric photochemistry and climate on Mars4. Recent observations of the water vapour abundance in the Martian atmosphere during dust storm conditions revealed a high-altitude increase in atmospheric water vapour that was more pronounced at high northern latitudes5,6, as well as a decrease in the water column at low latitudes7,8. Here we present concurrent, high-resolution measurements of dust, water and semiheavy water (HDO) at the onset of a global dust storm, obtained by the NOMAD and ACS instruments onboard the ExoMars Trace Gas Orbiter. We report the vertical distribution of the HDO/H2O ratio (D/H) from the planetary boundary layer up to an altitude of 80 kilometres. Our findings suggest that before the onset of the dust storm, HDO abundances were reduced to levels below detectability at altitudes above 40 kilometres. This decrease in HDO coincided with the presence of water-ice clouds. During the storm, an increase in the abundance of H2O and HDO was observed at altitudes between 40 and 80 kilometres. We propose that these increased abundances may be the result of warmer temperatures during the dust storm causing stronger atmospheric circulation and preventing ice cloud formation, which may confine water vapour to lower altitudes through gravitational fall and subsequent sublimation of ice crystals3. The observed changes in H2O and HDO abundance occurred within a few days during the development of the dust storm, suggesting a fast impact of dust storms on the Martian atmosphere.

Publisher Correction: Martian dust storm impact on atmospheric H2O and D/H observed by ExoMars Trace Gas Orbiter.

The surname of author Cathy Quantin-Nataf was misspelled 'Quantin-Nata' , authors Ehouarn Millour and Roland Young were missing from the ACS Science Team list, and minor changes have been made to the author and affiliation lists; see accompanying Amendment. These errors have been corrected online.

Reduction-triggered Disassembly of Organic Cationic Nanorods Produces a Cysteine Protease Mimic (Miravet et†al.).

The emergence of catalytic activity associated with a disassembly process is reported, reminiscent of complex biological systems. A cystine derivative with pendant imidazole groups self-assembles into cationic nanorods in the presence of the cationic surfactants cetylpyridinium chloride (CPC) or cetyltrimethylammonium bromide (CTAB). Disulfide reduction triggers nanorod disassembly and the generation of a simple cysteine protease mimic, which shows a dramatically improved catalytic efficiency in the hydrolysis of p-nitrophenyl acetate (PNPA).

Reduction-Responsive Cationic Vesicles from Bolaamphiphiles with Ionizable Amino Acid or Dipeptide Polar Heads.

This paper presents a study of the aggregation of cationic bolaamphiphilic molecules into vesicles. These molecules are based on a cystamine core with protonated terminal dipeptide groups. The study found that vesicles can be formed at pH 4 for all of the dipeptide-terminated bolaamphiphiles containing different combinations of l-valine, l-phenylalanine, and l-tryptophan. The concentration for aggregation onset was determined by using pyrene as a fluorescent probe or light dispersion for compounds with tryptophan. Dynamic light scattering (DLS) studies and transmission electron microscopy (TEM) reveal that the vesicles have diameters ranging from 140 to 500 nm and show the capability of loading hydrophobic cargos, such as Nile red, and their liberation in reductive environments. Furthermore, the bolaamphiphiles are only fully protonated and prone to vesicle formation at acidic pH, making them a promising alternative for gastrointestinal delivery.

Consensus document on acute-on-chronic liver failure (ACLF) established by the Mexican Association of Hepatology.

Acute-on chronic liver failure (ACLF) has been an intensively debated topic mainly due to the lack of a unified definition and diagnostic criteria. The growing number of publications describing the mechanisms of ACLF development, the progression of the disease, outcomes and treatment has contributed to a better understanding of the disease, however, it has also sparked the debate about this condition. As an attempt to provide medical professionals with a more uniform definition that could be applied to our population, the first Mexican consensus was performed by a panel of experts in the area of hepatology in Mexico. We used the most relevant and impactful publications along with the clinical and research experience of the consensus participants. The consensus was led by 4 coordinators who provided the most relevant bibliography by doing an exhaustive search on the topic. The entire bibliography was made available to the members of the consensus for consultation at any time during the process and six working groups were formed to develop the following sections: 1.- Generalities, definitions, and criteria, 2.- Pathophysiology of cirrhosis, 3.- Genetics in ACLF, 4.- Clinical manifestations, 5.- Liver transplantation in ACLF, 6.- Other treatments.

CEH-60/PBX regulates vitellogenesis and cuticle permeability through intestinal interaction with UNC-62/MEIS in Caenorhabditis elegans.

The onset of sexual maturity involves dramatic changes in physiology and gene expression in many animals. These include abundant yolk protein production in egg-laying species, an energetically costly process under extensive transcriptional control. Here, we used the model organism Caenorhabditis elegans to provide evidence for the spatiotemporally defined interaction of two evolutionarily conserved transcription factors, CEH-60/PBX and UNC-62/MEIS, acting as a gateway to yolk protein production. Via proteomics, bimolecular fluorescence complementation (BiFC), and biochemical and functional readouts, we show that this interaction occurs in the intestine of animals at the onset of sexual maturity and suffices to support the reproductive program. Our electron micrographs and functional assays provide evidence that intestinal PBX/MEIS cooperation drives another process that depends on lipid mobilization: the formation of an impermeable epicuticle. Without this lipid-rich protective layer, mutant animals are hypersensitive to exogenous oxidative stress and are poor partners for mating. Dedicated communication between the hypodermis and intestine in C. elegans likely supports these physiological outcomes, and we propose a fundamental role for the conserved PBX/MEIS interaction in multicellular signaling networks that rely on lipid homeostasis.

Development of a Polymeric Film Entrapping Rose Bengal and Iodide Anion for the Light-Induced Generation and Release of Bactericidal Hydrogen Peroxide.

A series of poly(2-hydroxyethyl methacrylate) (PHEMA) thin films entrapping photosensitizer Rose Bengal (RB) and tetrabutylammonium iodide (TBAI) have been synthetized. The materials have been characterized by means of Thermogravimetric Analysis (TGA), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) and UV-vis Absorption spectroscopy. Irradiation of the materials with white light led to the generation of several bactericidal species, including singlet oxygen (1O2), triiodide anion (I3-) and hydrogen peroxide (H2O2). 1O2 production was demonstrated spectroscopically by reaction with the chemical trap 2,2'-(anthracene-9,10-diylbis(methylene))dimalonic acid (ABDA). In addition, the reaction of iodide anion with 1O2 yielded I3- inside the polymeric matrix. This reaction is accompanied by the formation of H2O2, which diffuses out the polymeric matrix. Generation of both I3- and H2O2 was demonstrated spectroscopically (directly in the case of triiodide by the absorption at 360 nm and indirectly for H2O2 using the xylenol orange test). A series of photodynamic inactivation assays were conducted with the synthesized polymers against Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa. Complete eradication (7 log10 CFU/mL) of both bacteria occurred after only 5 min of white light irradiation (400-700 nm; total energy dose 24 J/cm2) of the polymer containing both RB and TBAI. The control polymer without embedded iodide (only RB) showed only marginal reductions of ca. 0.5 log10 CFU/mL. The main novelty of the present investigation is the generation of three bactericidal species (1O2, I3- and H2O2) at the same time using a single polymeric material containing all the elements needed to produce such a bactericidal cocktail, although the most relevant antimicrobial activity is shown by H2O2. This experimental approach avoids multistep protocols involving a final step of addition of I-, as described previously for other assays in solution.

NPY/NPF-Related Neuropeptide FLP-34 Signals from Serotonergic Neurons to Modulate Aversive Olfactory Learning in Caenorhabditis elegans.

Aversive learning is fundamental for animals to increase chances of survival. In addition to classical neurotransmitters, neuropeptides have emerged to modulate such complex behaviors. Among them, neuropeptide Y (NPY) is well known to promote aversive memory acquisition in mammals. Here we identify an NPY/neuropeptide F (NPF)-related neuropeptide system in Caenorhabditis elegans and show that this FLP-34/NPR-11 system is required for learning negative associations, a process that is reminiscent of NPY signaling in mammals. The Caenorhabditis elegans NPY/NPF ortholog FLP-34 displays conserved structural hallmarks of bilaterian-wide NPY/NPF neuropeptides. We show that it is required for aversive olfactory learning after pairing diacetyl with the absence of food, but not for appetitive olfactory learning in response to butanone. To mediate diacetyl learning and thus integrate the aversive food context with the diacetyl odor, FLP-34 is released from serotonergic neurons and signals through its evolutionarily conserved NPY/NPF GPCR, NPR-11, in downstream AIA interneurons. NPR-11 activation in the AIA integration center results in avoidance of a previously attractive stimulus. This study opens perspectives for a deeper understanding of stress conditions in which aversive learning results in excessive avoidance.SIGNIFICANCE STATEMENT Aversive learning evolved early in evolution to promote avoidance of dangerous and stressful situations. In addition to classical neurotransmitters, neuropeptides are emerging as modulators of complex behaviors, including learning and memory. Here, we identified the evolutionary ortholog of neuropeptide Y/neuropeptide F in the nematode Caenorhabditis elegans, and we discovered that it is required for olfactory aversive learning. In addition, we elucidated the neural circuit underlying this avoidance behavior, and we discovered a novel coordinated action of Caenorhabditis elegans neuropeptide Y/neuropeptide F and serotonin that could aid in our understanding of the molecular mechanisms underlying stress disorders in which excessive avoidance results in maladaptive behaviors.

Fluorescent styrylpyrylium probes for the imaging of mitochondria in live cells.

Eight styrylpyrylium tetrafluoroborate salts have been synthesized and fully optically characterized by UV-vis absorption and fluorescence steady-state/time-resolved spectroscopies. The new dyes exhibit strong emission bands with yellow-orange colours, depending on the substituents present in the structure. Notably, the Stokes shift recorded for some of them exceeds 100 nm, a very valuable feature for biological imaging. Four of them have been assayed as biological imaging agents by confocal laser scanning microscopy (CLSM) in the human hepatoma cell line Hep3B. It has been found that all the compounds efficiently stain intracellular structures which have been identified as mitochondria through colocalization assays with MitoView (a well-known mitochondrial marker) and using carbonyl cyanide m-chlorophenyl hydrazone (CCCP) as a mitochondrial membrane potential uncoupler. Additionally, the potential ability of the studied dyes as cytotoxic drugs has been explored. The inhibitory concentration (IC50) against Hep3B was found to be in the range of 4.2 µM-11.5 µM, similar to other described anticancer drugs for the same hepatoma cell line. The combined features of a good imaging agent and potential anticancer drug make the family of the studied pyrylium salts good candidates for further theranostic studies. Remarkably, despite the extensive use of pyrylium dyes in several scientific areas (from photocatalysis to optics), there is no precedent description of a styrylpyrylium salt with potential theranostic applications.

Liposome-Enveloped Molecular Nanogels.

Novel hydrogel@liposome particles were prepared by pH-triggered molecular gel formation inside of liposomes loaded with a low-molecular weight gelator derived from l-valine (1). Liposome formation was carried out using l-α-phosphatidylcholine (PC) and cholesterol as components of the lipid bilayer. Molecular hydrogelator 1 and pyranine, a ratiometric fluorescent pH probe, were entrapped in the liposomes at pH 9 and posterior acidification with d-glucono-1,5-lactone to pH 5-6 provoked intraliposomal gel formation. Removal of the lipid bilayer with sodium dodecyl sulfate yielded naked nanogel particles. The systems were characterized by transmission electron microscopy and dynamic light scattering. The hydrogel@liposomes were loaded with doxorubicin, showing a similar release than that observed for liposomes. The hybrid particles described here are the first case of nonpolymeric hydrogel@liposome systems reported. This type of nanocarriers merges the benefits of liposomal vehicles with the inherent stimuli responsiveness and enhanced biocompatibility of hydrogels formed by low-molecular weight molecules, foretelling a potential use in environmentally sensitive drug release.

In between molecules and self-assembled fibrillar networks: highly stable nanogel particles from a low molecular weight hydrogelator.

The preparation of molecular, non-polymeric nanogels from a low molecular weight hydrogelator is reported. The molecular nanogels are expected to overcome issues associated with the use of polymeric nanogels in biomedicine such as biodegradability, stimuli responsiveness, polydispersity, and batch-to-batch reproducibility. Nanogels formed by compound 1 were reproducibly prepared by sonication of a xerogel in PBS, with a total concentration of ca. 2 mM. The intensity averaged diameter of ca. 200 nm was determined by DLS. Electron microscopy (TEM and cryo-TEM) showed spherical particles. Light scattering (SALS) indicates that water is the main component of the nanoparticles, and the concentration of 1 in the nanogels is ca. 3 mg mL-1. These particles can be considered to constitute an intermediate state between free molecules and self-assembled fibrillar networks. The nanogels present excellent temporal and thermal stability and accessible hydrophobic domains, as demonstrated by the incorporation of the fluorescent dye Nile Red.

Photoactive Hexanuclear Molybdenum Nanoclusters Embedded in Molecular Organogels.

Hexanuclear molybdenum clusters are attractive species because of their outstanding photonic properties, and in the past they have been attached to a variety of supports such as organic polymers and inorganic nanoparticles, as described in the recent literature. Here, a cluster of the formula TBA2[Mo6I8Ac6] (TBA = tetrabutylammonium; Ac = acetate) has been supported on molecular organogels for the first time, resulting in a new soft material with remarkable photoactivity. Electron and confocal microscopic analyses showed the alignment of the nanoclusters to 1D self-assembled fibers formed by the organic gelator, and emission spectroscopy corroborated the interaction of the emissive clusters with such fibrillary structures. The new hybrid system is a deep-red emissive material (phosphorescence maximum at ca. 680 nm), with chromatic coordinates x = 0.725 and y = 0.274, capable of efficiently generating singlet oxygen (1O2) upon illumination with white light, as demonstrated by the photooxygenation of 9,10-dimethylanthracene and 1,5-dihydroxynaphthalene. The organogels can been made in dichloromethane and toluene and in both solvents display phosphorescence emission and photocatalytic properties.

Distribution of the bioavailable and total content of copper and lead, in river sediments of the Jamapa-Atoyac fluvial system, Mexico.

The Jamapa-Atoyac fluvial system (JAFS) is tropical river system, which flows from the Pico de Orizaba, the highest elevation in Mexico, to end in the city of Veracruz, in the southern Gulf of Mexico. The geology of the watershed is dominated by Tertiary igneous rocks and Cretaceous limestones in the upper basin, and Quaternary alluvial sediments in the lower basin. Seventy percent of the land in the watershed has been deforested, and there are various urban and industrial areas. The JAFS is been widely known as source of trace elements to the coastal zone, and considered as contaminated. So, the aim of this study was to assess the environmental quality of the JAFS, using the total (TC) and the bioavailable (BF) concentrations of Cu and Pb, in surface fluvial sediments samples, in the dry (DS) and rainy (RS) seasons of the 2016. Average concentrations and ranges for the JAFS were CuT 10.2 ± 5.2 µg/g (2.2-41.5 µg/g); CuB 1.1 ± 1.4 µg/g (0.04-10.7 µg/g); PbT 5.0 ± 1.2 µg/g (1.8-10.9 µg/g); and PbB 0.7 ± 0.4 µg/g (0.1-2.0 µg/g). The BF only accounts for the ~ 10% of the total concentration for both elements, and is highly correlated to the mud content. No differences in average concentrations were found between the upper and lower bassins, nor among areas with different lithology. Cu presented higher concentrations during the RS, which suggest an enrichment of fluvial sediments from soil erosion, contrary, to Pb with higher concentrations during the DS. Although, some sampling stations, those located immediately after the Cordoba and Miguel Aleman cities, presented higher than average Cu and Pb concentrations, they did not exceeded the limits established by national environmental regulations, sediment quality guidelines, geoaccumulation index, and potential ecological risk indexes. Hence, the JAFS may be considered as not contaminated by Cu and Pb.

Synthesis, spectroscopic studies and biological evaluation of acridine derivatives: The role of aggregation on the photodynamic efficiency.

Two new photoactive compounds (1 and 2) derived from the 9-amidoacridine chromophore have been synthesized and fully characterized. Their abilities to produce singlet oxygen upon irradiation have been compared. The synthesized compounds show very different self-aggregating properties since only 1 present a strong tendency to aggregate in water. Biological assays were conducted with two cell types: hepatoma cells (Hep3B) and human umbilical vein endothelial cells (HUVEC). Photodynamic therapy (PDT) studies carried out with Hep3B cells showed that non-aggregating compound 2 showed photoxicity, ascribed to the production of singlet oxygen, being aggregating compound 1 photochemically inactive. On the other hand suspensions of 1, characterized as nano-sized aggregates, have notable antiproliferative activity towards this cell line in the dark.

Sizing Down a Supramolecular Gel into Micro- and Nanoparticles.

A low molecular weight gelator with a fluorescent 1,8-naphthalimide unit forms micro- and nanoparticles in aqueous media. Slow addition of a DMSO solution of the gelator into water affords either a self-assembled fibrillar network, sheaf-like microparticles, or nanoparticles depending to the concentration used in the experiment. The micro- and nanoparticles were characterized by dynamic light scattering (DLS), electron microscopy, and fluorescence measurements. In an initial assay of particle loading, Rose Bengal and Rhodamine 123 were shown to be incorporated in the particles. Light-promoted singlet oxygen generation capabilities of Rose Bengal were modulated by its incorporation in the particles. Additionally, the particles were found to promote the transport of Rhodamine 123 into human lung carcinoma live cells. These results indicate that nanoparticles arising from low molecular weight gelators may represent a new type of nanocarriers, being a potential alternative to polymeric nanogels used in nanomedicine.

The interaction of amino acids with macrocyclic pH probes of pseudopeptidic nature.

The fluorescence quenching, by a series of amino acids, of pseudopeptidic compounds acting as probes for cellular acidity has been investigated. It has been found that amino acids containing electron-rich aromatic side chains like Trp or Tyr, as well as Met quench the emission of the probes mainly via a collisional mechanism, with Stern-Volmer constants in the 7-43 M-1 range, while other amino acids such as His, Val or Phe did not cause deactivation of the fluorescence. Only a minor contribution of a static quenching due to the formation of ground-state complexes has been found for Trp and Tyr, with association constants in the 9-24 M-1 range. For these ground-state complexes, a comparison between the macrocyclic probes and an open chain analogue reveals the existence of a moderate macrocyclic effect due to the preorganization of the probes in the more rigid structure.

Novel fluorescent anthracene-bodipy dyads displaying sensitivity to pH and turn-on behaviour towards Cu(ii) ions.

Three bichromophoric compounds containing anthracene and bodipy moieties connected by different spacers have been synthesized and fully characterized. The set of spacers comprises a variety of bridges (short and flexible 1,2-diaminoethane in compound 1a, long and flexible 1,8-diaminooctane in compound 1b and short and rigid piperazine in compound 1c). The new compounds show interchromophoric communication via Electronic Energy Transfer (EET). When anthracene is excited, the energy is efficiently transferred to the bodipy moiety. The emission of the acceptor is partially quenched in dyad 1a but remarkably not in 1b and 1c. In an aqueous environment, the fluorescence of the new compounds display sensitivity to pH (emissive at acidic values and non-emissive at neutral ones), a typical behaviour of photoinduced electron-transfer (PET) probes, but with remarkable differences in the pKa of each compound, attributable to the nature of the linker. Additionally, the behaviour in the presence of several metallic cations (Cu2+, Ni2+, Cd2+, Zn2+) has been studied, and a turn-on response towards Cu2+ in water at neutral pH has been found.

The synthesis of new fluorescent bichromophoric compounds as ratiometric pH probes for intracellular measurements.

Three different bichromophoric compounds (1-3) containing an aminomethyl anthracene moiety linked to a second chromophore (pyrene, 4-nitrobenzo-2-oxa-1,3-diazole (NBD) and dansyl) through a valine-derived pseudopeptidic spacer have been prepared and their fluorescent properties studied. The results obtained show that upon irradiation the photophysical behavior of these probes involves electronic energy transfer from the excited anthracene to the second chromophore and also intramolecular photoinduced electron transfer. The X-ray structure obtained for 3 reveals that the folding associated with the pseudopeptidic spacer favours a close proximity of the two chromophores. The emissive response of 3 is clearly dependent on the pH of the medium, hence this bichromophoric compound was shown to be an excellent ratiometric pH fluorescent sensor. The emission intensity due to the anthracene moiety exhibits a decrease at neutral-basic pH values that is concomitant with an increase in the intensity arising from the dansyl fluorophore. These properties make this compound a good candidate for biological pH sensing as has been confirmed by preliminary studies with RAW 264.7 macrophage cells imaged by means of confocal fluorescence microscopy with an average pH estimation of 5.4-5.8 for acidic organelles.

Recognition of free tryptophan in water by synthetic pseudopeptides: fluorescence and thermodynamic studies.

Pseudopeptidic receptors containing an acridine unit have been prepared and their fluorescence response to a series of amino acids was measured in water. Free amino acids, not protected either at the C or the N terminus, were used for this purpose. The prepared receptors display a selective response to tryptophan (Trp) versus the other assayed amino acids under acidic conditions. The macrocyclic nature of the receptor is important as the fluorescence quenching is higher for the macrocyclic compound than for the related open-chain receptor. Notably, under the experimental acidic conditions used, both the receptor and guest are fully protonated and positively charged; thus, the experimental results suggest the formation of supramolecular species that contain two positively charged organic molecular components in proximity stabilized through aromatic-aromatic interactions and a complex set of cation-anion-cation interactions. The selectivity towards Trp seems to be based on the existence of a strong association between the indole ring of the monocharged amino acid and the acridinium fragment of the triprotonated form of the receptor, which is established to be assisted by the interaction of the cationic moieties with hydrogen sulfate anions.

Fluorescent macrocyclic probes with pendant functional groups as markers of acidic organelles within live cells.

A new family of acidity sensitive fluorescent macrocycles has been synthesized and fully characterized. Their photophysical properties including emission quantum yield and fluorescence lifetime have been determined. The acid-base properties of the new molecules can be tuned by the incorporation of pendant functional groups. The nature of such functional groups (carboxylic acid or ester) influences dramatically the pKa of the probes, two compounds of which exhibit low values. Preliminary intracellular studies using confocal microscopy together with emission spectra of the probes from the cellular environment have shown that the synthesized fluorescent macrocycles mark the acidic organelles of RAW 264.7 macrophage cells.