Neuromolecular responses in disrupted mutualistic cleaning interactions under future environmental conditions.

BACKGROUND: Mutualistic interactions, which constitute some of the most advantageous interactions among fish species, are highly vulnerable to environmental changes. A key mutualistic interaction is the cleaning service rendered by the cleaner wrasse, Labroides dimidiatus, which involves intricate processes of social behaviour to remove ectoparasites from client fish and can be altered in near-future environmental conditions. Here, we evaluated the neuromolecular mechanisms behind the behavioural disruption of cleaning interactions in response to future environments. We subjected cleaner wrasses and surgeonfish (Acanthurus leucosternon, serving as clients) to elevated temperature (warming, 32 °C), increased levels of CO2 (high CO2, 1000 ppm), and a combined condition of elevated CO2 and temperature (warming and high CO2, 32 °C, and 1000 ppm) for 28 days. RESULTS: Each of these conditions resulted in behavioural disruptions concerning the motivation to interact and the quality of interaction (high CO2 - 80.7%, warming - 92.6%, warming and high CO2 - 79.5%, p < 0.001). Using transcriptomics of the fore-, mid-, and hindbrain, we discovered that most transcriptional reprogramming in both species under warming conditions occurred primarily in the hind- and forebrain. The associated functions under warming were linked to stress, heat shock proteins, hypoxia, and behaviour. In contrast, elevated CO2 exposure affected a range of functions associated with GABA, behaviour, visual perception, thyroid hormones and circadian rhythm. Interestingly, in the combined warming and high CO2 condition, we did not observe any expression changes of behaviour. However, we did find signs of endoplasmic reticulum stress and apoptosis, suggesting not only an additive effect of the environmental conditions but also a trade-off between physiological performance and behaviour in the cleaner wrasse. CONCLUSIONS: We show that impending environmental shifts can affect the behaviour and molecular processes that sustain mutualistic interactions between L. dimidiatus and its clients, which could have a cascading effect on their adaptation potential and possibly cause large-scale impacts on coral reef ecosystems.

Neuro-molecular characterization of fish cleaning interactions.

Coral reef fish exhibit a large variety of behaviours crucial for fitness and survival. The cleaner wrasse Labroides dimidiatus displays cognitive abilities during interspecific interactions by providing services of ectoparasite cleaning, thus serving as a good example to understand the processes of complex social behaviour. However, little is known about the molecular underpinnings of cooperative behaviour between L. dimidiatus and a potential client fish (Acanthurus leucosternon). Therefore, we investigated the molecular mechanisms in three regions of the brain (Fore-, Mid-, and Hindbrain) during the interaction of these fishes. Here we show, using transcriptomics, that most of the transcriptional response in both species was regulated in the Hindbrain and Forebrain regions and that the interacting behaviour responses of L. dimidiatus involved immediate early gene alteration, dopaminergic and glutamatergic pathways, the expression of neurohormones (such as isotocin) and steroids (e.g. progesterone and estrogen). In contrast, in the client, fewer molecular alterations were found, mostly involving pituitary hormone responses. The particular pathways found suggested synaptic plasticity, learning and memory processes in the cleaner wrasse, while the client indicated stress relief.

Acetylene Storage and Separation Using Metal-Organic Frameworks with Open Metal Sites.

Efficient separation and storage of gas streams involving light hydrocarbons is essential for industrial applications. These hydrocarbons are widely used as energy resources and/or chemical raw materials in various chemical reactions. Here, we focus on the separation of acetylene from methane and carbon dioxide. The separation of acetylene from carbon dioxide is, in particular, challenging due to the similar kinetic diameters and boiling points of the molecules. In recent years, considerable progress has been made in adsorption-based separations using porous metal-organic frameworks (MOFs). Most reported studies are experimental. We present a computational study on these gas separations using a variety of MOFs. This allows investigation of the competitive gas adsorption, which is experimentally challenging, as well as understanding the adsorption mechanisms at the molecular level, which in turn allows further experimental MOF design for this application. MOFs with open metal sites, and particularly Fe-MOF-74, seem to be good for this separation, with a trade-off between physical adsorption capacity and selectivity. Based on experimental single-adsorption isotherms at various temperatures, we developed and validated a specific parameterization to account for the interactions of the olefin with the open metal sites. In addition to volumetric and calorimetric adsorption, we comprehensively investigate the characteristics of the interaction between the MOFs and the guest molecules in terms of binding sites and density profiles. The overall agreement of our simulated results with experimental data for pure components points to the reliability of the models and methods to successfully predict the separation of mixtures.

Improving Olefin Purification Using Metal Organic Frameworks with Open Metal Sites.

The separation and purification of light hydrocarbons is challenging in the industry. Recently, a ZJNU-30 metal-organic framework (MOF) has been found to have the potential for adsorption-based separation of olefins and diolefins with four carbon atoms [H. M. Liu et al. Chem.-Eur. J. 2016, 22, 14988-14997]. Our study corroborates this finding but reveals Fe-MOF-74 as a more efficient candidate for the separation because of the open metal sites. We performed adsorption-based separation, transient breakthrough curves, and density functional theory calculations. This combination of techniques provides an extensive understanding of the studied system. Using this MOF, we propose a separation scheme to obtain a high-purity product.

Adsorption equilibrium of nitrogen dioxide in porous materials.

The effect of confinement on the equilibrium reactive system containing nitrogen dioxide and dinitrogen tetroxide is studied by molecular simulation and the reactive Monte Carlo (RxMC) approach. The bulk-phase reaction was successfully reproduced and five all-silica zeolites (i.e. FAU, FER, MFI, MOR, and TON) with different topologies were selected to study their adoption behavior. Dinitrogen tetroxide showed a stronger affinity than nitrogen dioxide in all the zeolites due to size effects, but exclusive adsorption sites in MOR allowed the adsorption of nitrogen dioxide with no competition at these sites. From the study of the adsorption isotherms and isobars of the reacting mixture, confinement enhanced the formation of dimers over the full range of pressure and temperature, finding the largest deviations from bulk fractions at low temperature and high pressure. The channel size and shape of the zeolite have a noticeable influence on the dinitrogen tetroxide formation, being more important in MFI, closely followed by TON and MOR, and finally FER and FAU. Preferential adsorption sites in MOR lead to an unusually strong selective adsorption towards nitrogen dioxide, demonstrating that the topological structure has a crucial influence on the composition of the mixture and must be carefully considered in systems containing nitrogen dioxide.

Micelle Formation in Aqueous Solutions of Room Temperature Ionic Liquids: A Molecular Dynamics Study.

1-Alkyl-3-methylimidazolium cations in the presence of water are used as a test system to study by molecular dynamics the formation of micelles in aqueous mixtures of highly anisotropic room temperature ionic liquids (IL). Structural properties, i.e., radial distribution functions (RDF) and transport parameters, such as diffusion coefficients and conductivities, are computed as a function of the IL/water mole fraction. The concentration plots reveal a sharp change of the slope of both the cation self-diffusion coefficient and the first peak of the head-head RDF at approximately the same value of the concentration. This transition, considered as a measure of a critical micellar concentration, appears only for the most anisotropic systems, composed of longer alkyl chains. The formation of the micelles is confirmed from the analysis of the tail-tail and cation-water RDFs. As a general result, we found that the larger the anisotropy of the ionic liquid the lower the critical concentration and the larger the proportion of monomers forming part of the micelles. The molecular dynamics predictions are in line with the experimental evidence reported for these systems.

Adsorptive process design for the separation of hexane isomers using zeolites.

The product of catalytic isomerization is a mixture of linear and branched hydrocarbons that are in thermodynamic equilibrium, and their separation becomes necessary in the petrochemical industry. Zeolite 5A is usually industrially used to sieve alkane isomers, but its pore size allows only the separation of linear alkanes from the monobranched and dibranched alkanes by a kinetic mechanism. A more efficient approach to improve the average research octane number would be to adsorptively separate the di-methyl alkanes as products and recycle both the linear and mono-methyl alkanes to the isomerization reactor. Since the microscopic processes of adsorbates in zeolites are generally difficult or impossible to determine by experiments, especially in the case of mixtures, molecular simulation represents an attractive alternative. In this computational study, we propose a conceptual separation process for hexane isomers consisting of several adsorptive steps. Different zeolite topologies were examined for their ability to conduct this separation based on adsorption equilibrium and kinetics.

Liquid self-diffusion of H2O and DMF molecules in Co-MOF-74: molecular dynamics simulations and dielectric spectroscopy studies.

In this work we use molecular dynamics simulations to study the diffusion of N,N-dimethylformamide (DMF) and H2O as a function of temperature within the well-known metal-organic framework Co2(dobdc)·[G] (G = 2DMF·1H2O), also known as Co-MOF-74. The molecular dynamics simulations show that the diffusivity of guest molecules, which is almost negligible at low temperatures (T < 200 K), increases in the range of 200 < T (K) < 400 up to 3 and 4 orders of magnitude for DMF and H2O, respectively. This molecular diffusion can be easily detected by dielectric spectroscopy as it gives rise to extrinsic interfacial polarization effects that result in an apparent "colossal" dielectric constant at room temperature, εr' ∼ 42 000 (T = 300 K, ν = 10 Hz). Furthermore, the measured dielectric constant exhibits a thermal dependence similar to that of the diffusion coefficient, revealing the parallelism of the dielectric response and the molecular diffusion as a function of temperature. These results highlight: (a) the great utility of the fast and non-destructive dielectric and impedance spectroscopy techniques for the study and detection of the molecular transport of small polar molecules within porous metal-organic frameworks and related materials; (b) the peculiarity and uniqueness of MOF materials with "medium" size nanopores containing guest molecules as they are solid materials in which the guest molecules display a liquid state-like behaviour close to room temperature; and

On the performance of FAU and MFI zeolites for the adsorptive removal of a series of volatile organic compounds from air using molecular simulation.

Volatile organic compound (VOC) emissions can cause serious risk to human health and the environment. In this work, we used Monte Carlo simulations to assess the performance of industrially important zeolites for the adsorption-based removal of a number of common air pollutants, particularly small saturated and unsaturated hydrocarbons: propane, butane, propene, and 1-butene. We focused on the cage-like FAU and channel-like MFI zeolites. The adsorption isotherms of the multicomponent N2/O2/Ar/VOC mixtures at real concentrations and room temperature reveal a considerable influence of the host topology and pore dimensions. While the adsorption of the VOCs from the mixture in FAU is almost negligible, it is remarkable in MFI. The adsorption selectivity of each VOC over the air compounds exhibits a maximum at about 10(6)-10(7) Pa, and then decreases to virtually zero due to entropic effects. This behaviour for selectivity is maintained regardless of the chain length and the presence of double bonds in the VOC, but the values are indeed affected. Also, we examined the selectivity at 10(7) Pa for a number of other widely used zeolites, with pore features ensuring the diffusion of the adsorbates. Apart from MFI, we also found the channel-like MEL and MTW zeolite candidates for the targeted air decontamination.

Transferable force fields for adsorption of small gases in zeolites.

We provide transferable force fields for oxygen, nitrogen, and carbon monoxide that are able to reproduce experimental adsorption in both pure silica and alumino-substituted zeolites at cryogenic and high temperatures. The force field parameters can be combined with those previously reported for carbon dioxide, methane, and argon, opening the possibility for studying mixtures of interest containing the six components. Using these force field parameters we obtained some adsorption isotherms at cryogenic temperatures that at first sight were in discrepancies with experimental values for certain molecules and structures. We attribute these discrepancies to the sensitiveness of the equipment and to kinetic impedimenta that can lead to erratic results. Additional problems can be found during simulations when extra-framework cations are present in the system as their lack of mobility at low temperatures could lead to kinetic effects that hinder experimental adsorption.

Zeolites for the selective adsorption of sulfur hexafluoride.

Molecular simulations have been used to investigate at the molecular level the suitability of zeolites with different topology on the adsorption, diffusion and separation of a nitrogen-sulfur hexafluoride mixture containing the latter at low concentration. This mixture represents the best alternative for the sulfur hexafluoride in industry since it reduces the use of this powerful greenhouse gas. A variety of zeolites are tested with the aim to identify the best structure for the recycling of sulfur hexafluoride in order to avoid its emission to the atmosphere and to overcome the experimental difficulties of its handling. Even though all zeolites show preferential adsorption of sulfur hexafluoride, we identified local structural features that reduce the affinity for sulfur hexafluoride in zeolites such as MOR and EON, providing exclusive adsorption sites for nitrogen. Structures such as ASV and FER were initially considered as good candidates based on their adsorption features. However, they were further discarded based on their diffusion properties. Regarding operation conditions for separation, the range of pressure that spans from 3 × 10(2) to 3 × 10(3) kPa was identified as the optimal to obtain the highest adsorption loading and the largest SF6/N2 selectivity. Based on these findings, zeolites BEC, ITR, IWW, and SFG were selected as the most promising materials for this particular separation.

Zeolite screening for the separation of gas mixtures containing SO2, CO2 and CO.

We used a combination of experiments and molecular simulations to investigate at the molecular level the effects of zeolite structure on the adsorption and diffusion of sulfur dioxide, carbon dioxide and carbon monoxide as well as separation processes of their mixtures. Our study involved different zeolite topologies and revealed numerous structure-property trends depending on the temperature and pressure conditions. Sulfur dioxide, which has the strongest interactions with zeolites due to its size and polarity, showed the largest adsorption across investigated temperatures and pressures. Our results indicate that structures with channel-type pore topology and low pore volume are the most promising for selective adsorption of sulfur dioxide over carbon dioxide and carbon monoxide under room conditions, while structures with higher pore volume exhibit better storage capacity at higher pressure. Our results emphasize the need for considering both adsorption and diffusion processes in the selection of the optimal structure for a given separation process. Our findings help to identify the best materials for effective separation processes under realistic operating conditions.

Optimisation of the Fischer-Tropsch process using zeolites for tail gas separation.

This work is aimed at optimizing a Fischer-Tropsch Gas To Liquid (GTL) process by recycling compounds of the expelled gas mixture using zeolites for the separation. To that end, we have performed a computational study on four structures widely used in industry. A range of Si/Al ratios have been explored and the effects of their distribution assessed. The ability of the considered force fields and molecular models to reproduce experimental results has been widely proved in previously reported studies. Since this tail gas is formed by a five-component mixture, namely carbon dioxide, methane, carbon monoxide, nitrogen and hydrogen, molecular simulations present clear advantages over experiments. In addition, the viability of the Ideal Adsorption Solution Theory (IAST) has been evaluated to easily handle further separation steps. On the basis of the obtained results, we provide a separation scheme to perform sequentially the separation of CO2, CH4, CO, N2 and H2.

Understanding Gas-Induced Structural Deformation of ZIF-8.

ZIF-8 is a zeolitic imidazolate framework with very good thermal and chemical stability that opens up many applications that are not feasible by other metal-organic frameowrks (MOFs) and zeolites. Several works report the adsorption properties of ZIF-8 for strategic gases. However, despite the vast experimental corpus of data reported, there seems yet to be a dearth in the understanding of the gas adsorption properties. In this work we provide insights at a molecular level on the mechanisms governing the ZIF-8 structural deformation during molecular adsorption. We demonstrate that the ZIF-8 structural deformation during the adsorption of different molecules at cryogenic temperature goes beyond the gas-induced rotation of the imidazolate linkers. We combine experimental and simulation studies to demonstrate that this deformation is governed by the polarizability and molecular size and shape of the gases, and that the stepped adsorption behavior is defined by the packing arrangement of the guest inside the host.

Computing the Heat of Adsorption using Molecular Simulations: The Effect of Strong Coulombic Interactions.

Molecular simulations are an important tool for the study of adsorption of hydrocarbons in nanoporous materials such as zeolites. The heat of adsorption is an important thermodynamic quantity that can be measured both in experiments and molecular simulations, and therefore it is often used to investigate the quality of a force field for a certain guest-host (g - h) system. In molecular simulations, the heat of adsorption in zeolites is often computed using either of the following methods: (1) using the Clausius-Clapeyron equation, which requires the partial derivative of the pressure with respect to temperature at constant loading, (2) using the energy difference between the host with and without a single guest molecule present, and (3) from energy/particle fluctuations in the grand-canonical ensemble. To calculate the heat of adsorption from experiments (besides direct calorimetry), only the first method is usually applicable. Although the computation of the heat of adsorption is straightforward for all-silica zeolites, severe difficulties arise when applying the conventional methods to systems with nonframework cations present. The reason for this is that these nonframework cations have very strong Coulombic interactions with the zeolite. We will present an alternative method based on biased interactions of guest molecules that suffers less from these difficulties. This method requires only a single simulation of the host structure. In addition, we will review some of the other important issues concerning the handling of these strong Coulombic interactions in simulating the adsorption of guest molecules. It turns out that the recently proposed Wolf method ( J. Chem. Phys. 1999, 110 , 8254 ) performs poorly for zeolites as a large cutoff radius is needed for convergence.

Influence of cation Na/Ca ratio on adsorption in LTA 5A: a systematic molecular simulation study of alkane chain length.

Recent adsorption isotherms of n-alkanes on Ca,Na-LTA-type zeolite afford development of a force field describing the interactions between calcium and n-alkanes in configurational-bias Monte Carlo simulations. The force field of Calero et al. (J. Am. Chem. Soc. 2004, 126, 11377-11386) is able to accurately describe the adsorption properties of linear alkanes in the sodium form of FAU-type zeolites. Here, we extend upon this type of force field by including calcium-type ions. The force field was fitted to reproduce the calcium and sodium cations positions on LTA 5A and the experimental adsorption properties of n-alkanes over all range of temperatures and pressures. This opens up a vast amount of experimental data on LTA 5A, both on adsorption and diffusion. Furthermore, evaluation of half a century of reported n-alkane adsorption data on LTA-type zeolites indicates that there are many inconsistencies between the various data sets, possibly as a result of (i) undisclosed calcium and sodium contents, (ii) less than perfect drying of the hygroscopic zeolite, and (iii) coadsorption of contaminants such as vacuum grease. Having obtained our force field, and confirmed its reliability on predictions outside the calibration set, we apply the force field on two "open" problems: (a) the heats of adsorption and Henry coefficient as a function of chain length and (b) the effect of cations in LTA-type zeolites. The molecular simulations shed new light on previous experimental findings, and we provide rationalizations on the molecular level that can be generalized to the class of cage/window-type nanoporous materials.

[Review of the interference between the most commonly prescribed drugs and clinical analyses at the Primary Health Care Centre of L'Hospitalet de Llobregat]. / Revisión de las interferencias entre los medicamentos más prescritos en el servicio de atención primaria de L'Hospitalet de Llobregat (ICS) y los análisis clínicos.

OBJECTIVE: To analyse the concordance of published information on probable drug interactions and the results of clinical analyses. DESIGN: Bibliographical review of the 50 most commonly prescribed drug products at the Primary Health Centre of L'Hospitalet de Llobregat, Barcelona, Spain, in 2002 and 2003. DATA SOURCE: Six bibliographical sources consisting of drug product catalogues and reference books. MEASUREMENTS: Interference with the 56 drug products studied. RESULTS: Most theoretical interference belonged to the therapeutic group of anti-inflammatory drugs. The drug products with most interference were hydrochlorothiazide (diuretic) and gliclazide (lipid lowering). The most frequent interference was in the increase of transaminases, thrombocytopaenia, leukopaenia, hyperglycaemia, and hyperuricaemia. Only in 12% of the points of interference analysed was the rate of concordance among the various bibliographical sources reviewed higher than 50%. The highest rate of concordance was found in the diuretics. CONCLUSIONS: Consultation of a single bibliographical source does not necessarily ensure the obtaining of reliable data on possible drug interference. This study demonstrates the need to standardize information on drug interference and to include the medication that the patient follows on the analysis application form.

A coarse-graining approach for the proton complex in protonated aluminosilicates.

We have developed a computational framework for the adsorption of linear alkanes in protonated aluminosilicates. These zeolites contain trace amounts of water that form hydrated proton complexes. The presence of hydrated protons makes the simulations at the fully atomistic level difficult. Instead of constructing an elaborate and complex model, we show that an approach based on a coarse-graining of the proton-complex accurately describes the available experimental isotherms, Henry coefficients, heats of adsorption, and oxygen-proton distances. Our approach is supported by MP2 quantum mechanical simulations. The model gives remarkably good agreement with experimental data beyond the initial calibration set.

Dynamically corrected transition state theory calculations of self-diffusion in anisotropic nanoporous materials.

We apply the dynamically corrected transition state theory to confinements with complex structures. This method is able to compute self-diffusion coefficients for adsorbate-adsorbent systems far beyond the time scales accessible to molecular dynamics. Two example cage/window-type confinements are examined: ethane in ERI- and CHA-type zeolites. In ERI-type zeolites, each hop in the z direction is preceded by a hop in xy direction and diffusion is anisotropic. The lattice for CHA-type zeolite is a rhombohedral Bravais lattice, and diffusion can be considered isotropic in practice. The anisotropic behavior of ERI-type cages reverses with loading, i.e., at low loading the diffusion in the z direction is two times faster than in the xy direction, while for higher loadings this changes to a z diffusivity that is more than two times slower. At low loading the diffusion is impeded by the eight-ring windows, i.e., the exits out of the cage to the next, but at higher loadings the barrier is formed by the center of the cages.

Revisión de las interferencias entre los medicamentos más prescritos en el servicio de atención primaria de L'Hospitalet de Llobregat (ICS) y los análisis clínicos / Review of the interference between the most commonly prescribed drugs and clinical analyses at the primary health care centre of L’Hospitalet de Llobregat (ICS)

Objetivo. Analizar la concordancia de la información publicada sobre probables interacciones medicamentosas con los resultados de las pruebas analíticas. Diseño. Revisión bibliográfica sobre los 50 medicamentos más prescritos en el servicio de atención primaria (SAP) de L'Hospitalet de Llobregat (Barcelona) durante los años 2002 y 2003. Fuente de datos. Seis fuentes bibliográficas consistentes en catálogos de especialidades farmacéuticas y libros de referencia. Selección de estudios. Interferencias que corresponden a los 56 medicamentos estudiados. Resultados. El mayor número de interferencias teóricas correspondió al grupo terapéutico de los antiinflamatorios. Los medicamentos con más interferencias fueron la hidroclorotiacida (diurético) y la gliclacida (hipoglucemiante). Las interferencias más frecuentes correspondieron al aumento de las transaminasas, la trombopenia, la leucopenia, la hiperglucemia y la hiperuricemia. Sólo en el 12% de las interferencias analizadas el grado de coincidencia entre las distintas fuentes bibliográficas consultadas fue superior al 50%. El mayor grado de coincidencia se dio en los diuréticos. Conclusiones. La consulta de una sola fuente bibliográfica no garantiza la obtención de una información fiable acerca de las posibles interferencias medicamentosas. El estudio pone de manifiesto la necesidad de uniformizar la información sobre las interferencias medicamentosas y de incluir en la solicitud analítica la medicación que utiliza el paciente

Objective. To analyse the concordance of published information on probable drug interactions and the results of clinical analyses. Design. Bibliographical review of the 50 most commonly prescribed drug products at the Primary Health Centre of L'Hospitalet de Llobregat, Barcelona, Spain, in 2002 and 2003. Data source. Six bibliographical sources consisting of drug product catalogues and reference books. Measurements. Interference with the 56 drug products studied. Results. Most theoretical interference belonged to the therapeutic group of anti-inflammatory drugs. The drug products with most interference were hydrochlorothiazide (diuretic) and gliclazide (lipid lowering). The most frequent interference was in the increase of transaminases, thrombocytopaenia, leukopaenia, hyperglycaemia, and hyperuricaemia. Only in 12% of the points of interference analysed was the rate of concordance among the various bibliographical sources reviewed higher than 50%. The highest rate of concordance was found in the diuretics. Conclusions. Consultation of a single bibliographical source does not necessarily ensure the obtaining of reliable data on possible drug interference. This study demonstrates the need to standardize information on drug interference and to include the medication that the patient follows on the analysis application form