Simulations of Adsorption of CO2 and CH4 in MOFs: Effect of the Size and Charge Distribution on the Selectivity

Using the method of Grand Canonical Monte Carlo we have computed the adsorption of CO₂ and CH₄ in MOFs with a periodic cubic structure. We used a model of the MOF that allows systematic variations in the charge distribution, size and LJ parameters. We estimated the selectivity of CO₂ over CH₄ for different temperatures in MOFs with various sizes and charge distributions. The results show that inserting dipoles at the corners of the MOF’s unit cell would increase the selectivity of CO₂; on the other hand adding quadrupoles to the structure is ineffective. The size of the cell strongly affects the adsorption of CO₂ and selectivity: compressing the cell in only 10 % significantly increases the selectivity; expanding the cell by 20 % reduces it. Regarding thermal effects, we estimated that the selectivity drops from 250 to 2 when the temperature rises from 120 K to 300 K. Although this model is inspired by the IRMOF-1, which has a cubic unit cell, it can be adapted to represent other MOFs with noncubic structures by modifying the geometry accordingly. This work implies that MOFs suit gas separation.     

FAAS determination of metal nutrients in fish feed after ultrasound extraction

This paper proposes a method to determine calcium, magnesium, manganese and zinc in fish feed samples using ultrasound in the analyte extraction process, and subsequent quantification by flame atomic absorption spectrometry (FAAS). Using 0.10 mol/L of HCl as extraction solution, the optimal conditions of extraction were established as follows: 100 mg of sample mass; sample granulometry of less than 60 μm; sonication time of three cycles of 10 s and sonication power of 102 W. The method was applied in studies of the digestibility of these nutrients in samples of fish feed used in the diet of Nile tilapia juveniles. The results achieved were congruent with those obtained from the mineralization of fish feed samples in the metal nutrient extraction process.     

Membrane Association Modes of Natural Anticancer Peptides: Mechanistic Details on Helicity,Orientation, and Surface Coverage

Anticancer peptides (ACPs) could potentially offer many advantages over other cancer therapies. ACPs often target cell membranes, where their surface mechanism is coupled to a conformational change into helical structures. However, details on their binding are still unclear, which would be crucial to reach progress in connecting structural aspects to ACP action and to therapeutic developments. Here we investigated natural helical ACPs, Lasioglossin LL-III, Macropin 1, Temporin-La, FK-16, and LL-37, on model liposomes, and also on extracellular vesicles (EVs), with an outer leaflet composition similar to cancer cells. The combined simulations and experiments identified three distinct binding modes to the membranes. Firstly, a highly helical structure, lying mainly on the membrane surface; secondly, a similar, yet only partially helical structure with disordered regions; and thirdly, a helical monomeric form with a non-inserted perpendicular orientation relative to the membrane surface. The latter allows large swings of the helix while the N-terminal is anchored to the headgroup region. These results indicate that subtle differences in sequence and charge can result in altered binding modes. The first two modes could be part of the well-known carpet model mechanism, whereas the newly identified third mode could be an intermediate state, existing prior to membrane insertion.     

Effect of the crosslink functionality on the mechanical properties of crosslinked 1,2,3‐triazole polymers as potential binders for rocket propellants

The mechanical properties of crosslinked polymers depend on their structural features, one of which is the functionality of the crosslinks in a polymer network. To study the effect of crosslink functionality (?) on the mechanical properties of 1,2,3‐triazole polymers for potential application as rocket propellant binders, crosslinkers with different ?'s (3, 4, 6, 16, 32, and 64) were used in the polymerization. As the percentage of acetylenic groups provided by crosslinker was kept constant and the functionality of the crosslinker increased, the resulting polymer showed a higher modulus but a lower strain. Compared to traditional polyurethane binders, 1,2,3‐triazole polymers showed comparable mechanical properties, although the stress and modulus tended to be lower and the strain capability tended to be greater for the triazole‐linked rubbers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermodiffusion in Ternary Mixtures of Water/Ethanol/Triethylene Glycol: First Report on the DCMIX3-Experiments Performed on the International Space Station

We report on thermodiffusion experiments conducted on the International Space Station ISS during fall 2016. These experiments are part of the DCMIX (Diffusion and thermodiffusion Coefficients Measurements in ternary Mixtures) project, which aims at establishing a reliable data base of non-isothermal transport coefficients for selected ternary liquid mixtures. The third campaign, DCMIX3, focuses on aqueous systems with water/ethanol/triethylene glycol as an example, where sign changes of the Soret coefficient have already been reported for certain binary subsystems. Investigations have been carried out with the SODI (Selectable Optical Diagnostics Instrument) instrument, a Mach-Zehnder interferometer set up inside the Microgravity Science Glovebox in the Destiny Module of the ISS. Concentration changes within the liquids have been monitored in response to an external temperature gradient using phase-stepping interferometry. The complete data set has been made available in spring 2017. Due to additionally available measurement time, it was possible to collect a complete data set at 30^°C and an almost complete data set at 25^°C, which significantly exceeds the originally envisaged measurements at a single temperature only. All samples could be measured successfully. The SODI instrument and the DCMIX experiments have proven reliable and robust, allowing to extract meaningful data even in case of unforeseen laser instabilities. First assessments of the data quality have revealed six out of 31 runs with some problems in image contrast and/or phase step stability that will require more sophisticated algorithms. This publication documents all relevant parameters of the conducted experiments and also events that might have an influence on the final results. The compiled information is intended to serve as a starting point for all following data evaluations.     

Ozonation of Cisplatin in Aqueous Solution at pH 9

Ozonation of cisplatin [cis-diamminedichloroplatinum (II)] in non-buffered and buffered aqueous solutions at pH 9 was carried out at 303 K in a semi batch system at laboratory scale. The degradation of cisplatin and the formation of reaction products were analyzed by reverse phase high performance liquid chromatography. In the first two minutes of reaction practically all the initial cisplatin was depleted and only one major peak was observed in chromatograms under both experimental conditions. The structure of this main product was proposed after analysis by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The mutagenicity of reaction mixture at non-buffered pH 9 was evaluated by performing Ames test. Non-mutagenic effect was observed. The second-order reaction rate constant of cisplatin with hydroxyl radical at pH 9 and 303 K was determined.     

Manipulating Active Structure and Function of Cationic Antimicrobial Peptide CM15 with the Polysulfonated Drug Suramin: A Step Closer to in Vivo Complexity

Antimicrobial peptides (AMPs) kill bacteria by targeting their membranes through various mechanisms involving peptide assembly, often coupled with disorder-to-order structural transition. However, for several AMPs, similar conformational changes in cases in which small organic compounds of both endogenous and exogenous origin have induced folded peptide conformations have recently been reported. Thus, the function of AMPs and of natural host defence peptides can be significantly affected by the local complex molecular environment in vivo; nonetheless, this area is hardly explored. To address the relevance of such interactions with regard to structure and function, we have tested the effects of the therapeutic drug suramin on the membrane activity and antibacterial efficiency of CM15, a potent hybrid AMP. The results provided insight into a dynamic system in which peptide interaction with lipid bilayers is interfered with by the competitive binding of CM15 to suramin, resulting in an equilibrium dependent on peptide-to-drug ratio and vesicle surface charge. In vitro bacterial tests showed that when CM15 ⋅ suramin complex formation dominates over membrane binding, antimicrobial activity is abolished. On the basis of this case study, it is proposed that small-molecule secondary structure regulators can modify AMP function and that this should be considered and could potentially be exploited in future development of AMP-based antimicrobial agents.     

Optimization of the Fermentation of Cantaloupe Juice by Lactobacillus casei NRRL B-442

This study was carried out to optimize the fermentation pH and temperature and also the fermentation time for development of a new probiotic fermented drink with cantaloupe juice. The fermented juice was subjected to a storage study during 42?days at 4?°C. The initial pH and temperature influenced the growth of Lactobacillus casei in cantaloupe juice. However, on the microbial viability only the effect of temperature was significant. Optimum conditions for a satisfactory growth and viability of L. casei in cantaloupe juice were as follows: pH?=?6.1 and temperature?=?31?°C. The fermentation time of 8 hours was selected as the optimal fermentation time to prepare the probiotic cantaloupe juice. The cell viability was 8.3 log CFU mL^?1 at the end of the fermentation. This level was kept over the 42?days of refrigerated storage. The consistent growth and viability of the probiotic microorganism in cantaloupe juice during fermentation and storage suggested that melon is a suitable vehicle for L. casei delivering. The fermented juice arises as a good alternative to the traditional dairy based products.