Orthogonal Peptide-Templated Labeling Elucidates Lateral ETAR/ETBR Proximity and Reveals Altered Downstream Signaling

Fine-tuning of G protein-coupled receptor (GPCR) signaling is important to maintain cellular homeostasis. Recent studies demonstrated that lateral GPCR interactions in the cell membrane can impact signaling profiles. Here, we report on a one-step labeling method of multiple membrane-embedded GPCRs. Based on short peptide tags, complementary probes transfer the cargo (e. g. a fluorescent dye) by an acyl transfer reaction with high spatial and temporal resolution within 5 min. We applied this approach to four receptors of the cardiovascular system: the endothelin receptor A and B (ET_AR and ET_BR), angiotensin II receptor type 1, and apelin. Wild type-like G protein activation after N-terminal modification was demonstrated for all receptor species. Using FRET-competent dyes, a constitutive proximity between hetero-receptors was limited to ET_AR/ET_BR. Further, we demonstrate, that ET_AR expression regulates the signaling of co-expressed ET_BR. Our orthogonal peptide-templated labeling of different GPCRs provides novel insight into the regulation of GPCR signaling.     

Lipolysis in dry cured sausages as affected by processing conditions

Changes of phospholipids and free fatty acids during fermentation and ripening steps of the Spanish dry cured sausage ('salchichón') process have been analyzed by studying the effects of manufacturing conditions; namely starter addition, pre-ripening and drying temperature. Phospholipid concentration of all types of samples considered (with or without starter, preripened or not) showed no important changes during fermentation, but different behaviour was observed during ripening in relation to sample type and drying temperature. At 8 °C concentrations did not change in sausages without starter and suffered a moderate decrease in samples with starter. At 16 °C the decrease was pronounced in samples without starter and much more in those with starter. Pre-ripening had no effect on phospholipid concentration. Free fatty acids increase slightly with pre-ripening, but during fermentation pre-ripened samples showed no more variation, whereas in non-preripened samples an important increase was observed. These results were similar in samples with and without starter. During the ripening step, samples with starter dried at 8 °C showed a higher increase of free fatty acids than those without starter, with no influence of the pre-ripening. At 16 °C all samples showed a higher increase than any sample dried at 8 °C. The maximum was found with non-preripened samples without starter and the minimum with pre-ripened ones, also without starter. Sausages with starter showed an intermediate increase with no effect of pre-ripening.     

A novel experimental investigation of a solar cooling system in Madrid

This paper reports novel experimental results derived through field testing of a part load solar energized cooling system for typical Spanish houses in Madrid during the summer period of 2003. Solar hot water was delivered by means of a 49.9 m² array of flat-plate collectors to drive a single-effect (LiBr/H₂O) absorption chiller of 35 kW nominal cooling capacity. Thermal energy was stored in a 2 m³ stratified hot water storage tank during hours of bright sunshine. Chilled water produced at the evaporator was supplied to a row of fan coil units and the heat of condensation and absorption was rejected by means of a forced draft cooling tower. Instantaneous, daily and period energy flows and energy balance in the installation is presented. System and absorption machine temperature profiles are given for a clear, hot and dry day's operation. Daily and period system efficiencies are given. Peak insolation of 969 W m⁻² (at 12:30 solar time on 08/08/03) produced 5.13 kW of cooling at a solar to cooling conversion efficiency of 11%. Maximum cooling capacity was 7.5 kW. Cooling was provided for 8.67 h and the chiller required a threshold insolation of 711 W m⁻² for start-up and 373 W m⁻² for shut-down. A minimum hot water inlet temperature to the generator of 65 °C was required to commence cold generation, whereas at 81 °C, 6.4 kW of cooling (18.3% of nominal capacity) was produced. The absorption refrigeration machine operated within the generation and absorption temperature ranges of 57–67 and 32–36 °C, respectively. The measured maximum instantaneous, daily average and period average COP were 0.60 (at maximum capacity), 0.42 and 0.34, respectively. Energy flows in the system are represented on a novel area diagram. The results clearly demonstrate that the technology works best in dry and hot climatic conditions where large daily variations in relative humidity and dry bulb temperature prevail. This case study provides benchmark data for the assessment of other similar prototypes and for the validation of mathematical models.     

The effects of behavioral tasks on the in vitro phosphorylation of intermediate filament subunits of rat hippocampus are mediated by CaMKII and PKA

In the homodimeric hemoglobin from Scapharca, HbI, functional communication between the two heme groups is based on their direct structural linkage across the subunit interface through the heme propionates. The heme-protein interactions have been altered in deutero- and meso-HbI by substituting the vinyl groups at positions 2 and 4 of protoheme with hydrogen and ethyl groups, respectively. In meso-HbI the introduction of the ethyl groups in the heme pocket induces significant alterations in the conformation of the heme peripheral substituents, including the propionates, and in the structure of bound CO, as revealed by the resonance Raman spectra. The functional counterpart of these structural changes is the loss of cooperativity in carbon monoxide binding and in the rate of oxygen dissociation. Oxygen pulse and flash photolysis experiments indicate that meso-HbI is locked in the liganded conformation. It is postulated that the ethyl groups, which occupy a larger volume than vinyl ones, impair the ligand-linked movement of the heme relative to its pocket and in turn the expression of cooperativity. In deutero-HbI structural alterations have not been monitored. Functionally, cooperativity in the CO binding kinetics is increased as if hydrogen atoms at positions 2 and 4 permitted more marked movements of the heme than in the native protein.     

Influence of CTAB on the electrochemical behavior of dopamine and on its analytic determination in the presence of ascorbic acid

This research work concerns the electrochemical study of dopamine and ascorbic acid in the presence of the cationic surfactant cetyltrimethylammonium bromide. From this study is possible to note that the cetyltrimethylammonium bromide greatest influence was on the dopamine, because it disfavors both its oxidation and reduction, thereby giving a smaller heterogeneous rate constant, k ⁰, value than in its absence, provoking that the process tends to irreversibility. On the contrary, for the ascorbic acid case, its oxidation was favored; these effects can influence the separation of the dopamine and ascorbic acid voltammetric signals up to 453 mV. Further, the method could be optimized through differential pulse voltammetry to proceed with the analytic determination of dopamine in the presence of ascorbic acid displaying usable analytic parameters, namely: a linearity range of 0–130 μM, a sensitivity of (6.318 ± 0.002) μA mM^?1, a detection limit of (11 ± 0.1) μM, and a quantification limit of (37 ± 0.2) μM, which made it possible to effect the quantification on a commercial pharmaceutical sample.     

Contribution of the Tyr-1 in Plantaricin149a to Disrupt Phospholipid Model Membranes

Plantaricin149a (Pln149a) is a cationic antimicrobial peptide, which was suggested to cause membrane destabilization via the carpet mechanism. The mode of action proposed to this antimicrobial peptide describes the induction of an amphipathic α-helix from Ala7 to Lys20, while the N-terminus residues remain in a coil conformation after binding. To better investigate this assumption, the purpose of this study was to determine the contributions of the Tyr1 in Pln149a in the binding to model membranes to promote its destabilization. The Tyr to Ser substitution increased the dissociation constant (K_D) of the antimicrobial peptide from the liposomes (approximately three-fold higher), and decreased the enthalpy of binding to anionic vesicles from −17.2 kcal/mol to −10.2 kcal/mol. The peptide adsorption/incorporation into the negatively charged lipid vesicles was less effective with the Tyr1 substitution and peptide Pln149a perturbed the liposome integrity more than the analog, Pln149S. Taken together, the peptide-lipid interactions that govern the Pln149a antimicrobial activity are found not only in the amphipathic helix, but also in the N-terminus residues, which take part in enthalpic contributions due to the allocation at a lipid-aqueous interface.     

Interference of EDTA in the treatment of metal plating wastewater by biosorption

BACKGROUND: The applicability of biosorption for the treatment of metal plating wastewater is adversely affected by the presence of complexing agents. To investigate this limitation on the removal of copper(II) onto peat, batch and column experiments were carried out using EDTA as the model complexing agent. The influence of pH and copper(II):EDTA mass ratios were evaluated for copper(II) concentrations between 5 and 100 mg Cu(II) dm^?3. RESULTS: EDTA negatively affected the copper(II) uptake of peat for pH > 5. Batch and column experiments showed that copper(II)‐EDTA complexes were not sorbed by peat. The leaks of copper(II) detected from the beginning of the column operation matched the copper(II)‐EDTA concentration in the feed solutions. To overcome the interference of EDTA, a novel approach based on the combination of peat + activated carbon was proposed. Nearly complete removal of copper(II) was maintained over 70 h in the treatment of a solution containing 20 mg Cu(II) dm^?3 with 11% of copper(II)‐EDTA complexes. CONCLUSION: A new mass transport model coupling copper(II) speciation in the feed and mass transfer rate‐controlled process simulated the copper(II) breakthrough curves in the presence of EDTA and could be used to successfully predict the breakthrough point. This work demonstrated that biosorption can also be applied for the treatment of wastewater containing complexing agents with the proper combination of sorbent materials. © 2012 Society of Chemical Industry     

An open-source library for the numerical modeling of mass-transfer in solid oxide fuel cells

The generation of direct current electricity using solid oxide fuel cells (SOFCs) involves several interplaying transport phenomena. Their simulation is crucial for the design and optimization of reliable and competitive equipment, and for the eventual market deployment of this technology. An open-source library for the computational modeling of mass-transport phenomena in SOFCs is presented in this article. It includes several multicomponent mass-transport models (i.e. Fickian, Stefan–Maxwell and Dusty Gas Model), which can be applied both within porous media and in porosity-free domains, and several diffusivity models for gases. The library has been developed for its use with OpenFOAM^®, a widespread open-source code for fluid and continuum mechanics. The library can be used to model any fluid flow configuration involving multicomponent transport phenomena and it is validated in this paper against the analytical solution of one-dimensional test cases. In addition, it is applied for the simulation of a real SOFC and further validated using experimental data.Program summaryProgram title: multiSpeciesTransportModelsCatalogue identifier: AEKB_v1_0Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEKB_v1_0.htmlProgram obtainable from: CPC Program Library, Queen?s University, Belfast, N. IrelandLicensing provisions: GNU General Public LicenseNo. of lines in distributed program, including test data, etc.: 18 140No. of bytes in distributed program, including test data, etc.: 64 285Distribution format: tar.gzProgramming language:: C++Computer: Any x86 (the instructions reported in the paper consider only the 64 bit case for the sake of simplicity)Operating system: Generic Linux (the instructions reported in the paper consider only the open-source Ubuntu distribution for the sake of simplicity)Classification: 12External routines: OpenFOAM® (version 1.6-ext) (http://www.extend-project.de)Nature of problem: This software provides a library of models for the simulation of the steady state mass and momentum transport in a multi-species gas mixture, possibly in a porous medium. The software is particularly designed to be used as the mass-transport library for the modeling of solid oxide fuel cells (SOFC). When supplemented with other sub-models, such as thermal and charge-transport ones, it allows the prediction of the cell polarization curve and hence the cell performance.Solution method: Standard finite volume method (FVM) is used for solving all the conservation equations. The pressure-velocity coupling is solved using the SIMPLE algorithm (possibly adding a porous drag term if required). The mass transport can be calculated using different alternative models, namely Fick, Maxwell–Stefan or dusty gas model. The code adopts a segregated method to solve the resulting linear system of equations. The different regions of the SOFC, namely gas channels, electrodes and electrolyte, are solved independently, and coupled through boundary conditions.Restrictions: When extremely large species fluxes are considered, current implementation of the Neumann and Robin boundary conditions do not avoid negative values of molar and/or mass fractions, which finally end up with numerical instability. However this never happened in the documented runs. Eventually these boundary conditions could be reformulated to become more robust.Running time: From seconds to hours depending on the mesh size and number of species. For example, on a 64 bit machine with Intel Core Duo T8300 and 3 GBytes of RAM, the provided test run requires less than 1 second.     

Using AVAL-1D to simulate avalanches in the eastern Pyrenees

The two friction parameters used in the numerical avalanche dynamics program AVAL-1D, were calibrated empirically with data from observed avalanches in the Swiss Alps. The implementation of the model with these friction parameters in other regions with different characteristics can lead to considerable uncertainty if a previous calibration is not performed. However, direct calibration for a specific avalanche path is often not possible since the data available are insufficient. Therefore, we back-calculated twelve well-documented avalanche events from the Catalan Pyrenees to calibrate the friction coefficients to be used in this mountain range. The result of the study reveals that there is a good fit between recorded and simulated avalanche events using the friction parameters originally calibrated for the Swiss Alps, despite the difference in snow climate between these two mountain ranges.