Tuning ubiquinone position in biomimetic monolayer membranes

Artificial lipid bilayers have been extensively studied as models that mimic natural membranes (biomimetic membranes). Several attempts of biomimetic membranes inserting ubiquinone (UQ) have been performed to enlighten which the position of UQ in the lipid layer is, although obtaining contradictory results. In this work, pure components (DPPC and UQ) and DPPC:UQ mixtures have been studied using surface pressure-area isotherms and Langmuir-Blodgett (LB) films of the same compounds have been transferred onto solid substrates being topographically characterized on mica using atomic force microscopy and electrochemically on indium tin oxide slides. DPPC:UQ mixtures present less solid-like physical state than pure DPPC indicating a higher-order degree for the latter. UQ influences considerably DPPC during the fluid state, but it is mainly expelled after the phase transition at ˜˜ 26 mN·m^-1 for the 5:1 ratio and at ˜˜ 21 mN·m^-1 for lower UQ content. The thermodynamic studies confirm the stability of the DPPC:UQ mixtures before that event, although presenting a non-ideal behaviour. The results indicate that UQ position can be tuned by means of the surface pressure applied to obtain LB films and the UQ initial content. The UQ positions in the biomimetic membrane are distinguished by their formal potential: UQ located in “diving” position with the UQ placed in the DPPC matrix in direct contact with the electrode surface ( -0.04±0.02 V), inserted between lipid chains without contact to the substrate ( 0.00±0.01 V) and parallel to the substrate, above the lipid chains ( 0.09±0.02 V).Peer ReviewedPostprint (author's final draft

Environmental chemical sensing using small drones: A review

Recent advances in miniaturization of chemical instrumentation and in low-cost small drones are catalyzing exponential growth in the use of such platforms for environmental chemical sensing applications. The versatility of chemically sensitive drones is reflected by their rapid adoption in scientific, industrial, and regulatory domains, such as in atmospheric research studies, industrial emission monitoring, and in enforcement of environmental regulations. As a result of this interdisciplinarity, progress to date has been reported across a broad spread of scientific and non-scientific databases, including scientific journals, press releases, company websites, and field reports. The aim of this paper is to assemble all of these pieces of information into a comprehensive, structured and updated review of the field of chemical sensing using small drones. We exhaustively review current and emerging applications of this technology, as well as sensing platforms and algorithms developed by research groups and companies for tasks such as gas concentration mapping, source localization, and flux estimation. We conclude with a discussion of the most pressing technological and regulatory limitations in current practice, and how these could be addressed by future research

Global Calibration Models for Temperature-Modulated Metal Oxide Gas Sensors: A Strategy to Reduce Calibration Costs

Tolerances in the fabrication of metal oxide (MOX) gas sensors lead to inter-device variability in baseline and sensitivity, even for sensors of the same fabrication batch. This has traditionally forced the use of individual calibration models (ICMs) built specifically for each sensor unit, which requires an expensive and time-consuming calibration process and hinders sensor replacement. We propose Global calibration models (GCMs) built using the responses of multiple sensor units, and then applied to a new sensor unit that is not part of the calibration set. GCM have been already successfully applied to transfer calibration models between sensor arrays (electronic noses) for classification tasks. In this work, we investigate the use of such models for regression purposes in temperature-modulated sensors, aiming at the quantification of low concentrations of carbon monoxide (CO) in the presence of variable humidity levels (20–80% r.h. at 26 ± 1 °C). Using a laboratory dataset containing data from 6 replicas of the FIS SB-500–12 model, we evaluate the performance of global models built with data from 1 to 4 sensors when applied to unseen sensor units. Results show that the performance of global models improves with an increasing number of sensors in the calibration set, approaching the performance of individual calibration models (1.38 ± 0.15 ppm for GCM; 1.05 ± 0.24 ppm for ICM), and surpassing their performance only if few calibration conditions per sensor are available (2.09 ± 0.10 ppm for GCM;; 2.76 ± 0.22 ppm for ICM, if only 5 samples per sensor are used).We would like to acknowledge, the Departament d’Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya (expedient 2017 SGR 1721); the Comissionat per a Universitats i Recerca del DIUE de la Generalitat de Catalunya; and the European Social Fund (ESF). Additional financial support has been provided by the Institut de Bioenginyeria de Catalunya (IBEC). IBEC is a member of the CERCA Programme/Generalitat de Catalunya

Monogalactosyldiacylglycerol and digalactosyldiacylglycerol role, physical states, applications and biomimetic monolayer films

The relevance of biomimetic membranes using galactolipids has not been expressed in any extensive experimental study of these lipids. Thus, on the one hand, we present an in-depth article about the presence and role of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) in thylakoid membranes, their physical states and their applications. On the other hand, we use the Langmuir and Langmuir-Blodgett (LB) techniques to prepare biomimetic monolayers of saturated galactolipids MGDG, DGDG and MGDG:DGDG 2:1 mixture (MD)-biological ratio-. These monolayers are studied using surface pressure-area isotherms and their data are processed to enlighten their physical states and mixing behaviour. These monolayers, once transferred to a solid substrate at several surface pressures are topographically studied on mica using atomic force microscopy (AFM) and using cyclic voltammetry for studying the electrochemical behaviour of the monolayers once transferred to indium-tin oxide (ITO), which has good optical and electrical properties. Moreover, MD presents other differences in comparison with its pure components that are explained by the presence of different kinds of galactosyl headgroups that restrict the optimal orientation of the MGDG headgroups.Peer ReviewedPostprint (published version

Influence of membrane galactolipids and surface pressure on plastoquinone behaviour

In this work biomimetic monolayers of a MGDG, monogalactosyldiacylglycerol, and DGDG, digalactosyldiacylglycerol mixture (MD), in a ratio close to that of the thylakoid membranes of oxygenic photosynthetic organisms, have been prepared. The lipid mixture incorporates plastoquinone-9 (PQ), that is the election and proton shuttle of the photosynthetic reaction centres. The MD:PQ mixtures have been firstly studied using surface pressure-area isotherms. Langmuir-Blodgett (LB) films of those mixtures have been transferred onto a substrate forming a monolayer that mimics one of the bilayer sides of the thylakoid membranes. These monolayers have been characterized topographically and electrochemically. The results show the influence of PQ in the MD matrix and its partial expulsion when increasing the surface pressure, obtaining two main PQ positions in the MD matrix. The calculated apparent electron transfer rate constants indicate a different kinetic control for the reduction and the oxidation of the PQ/PQH(2) couple, being k(Rapp)(I) = 0.7 . 10(-6) s(-1), k(Rapp)(II) = 2.2 . 10(-9) s(-1), k(Oapp)(I) = 7.4 . 10(-4) s(-1) and k(Oapp)(II) = 5.2 . 10(-5) s(-1), respectively. The comparison of the different galactolipid:PQ systems that our group has studied is also presented, concluding that the PQ position in the galactolipid matrix can be tuned according to several controlled variables. (C) 2016 Elsevier B.V. All rights reserved.Peer ReviewedPostprint (author's final draft

Using non-functional requirements in component-based software construction

The main concern of this paper is to present the author's approach to support software development in the component programming framework taking functional and non-functional requirements into account. Functional requirements are written as algebraic specifications, while non-functional information is bound to specifications and implementations by means of ad hoc modules: the nonfunctional information is used to select automatically the most appropriate implementations of software components (the selection algorithm is not presented here). The existence of multiple type implementations is supported by a process model based on the prototyping paradigm. Prototyping is achieved by means of a mixed execution mechanism being able to operate in the context of incremental software development process allowing the execution of incomplete (partially implemented) systems. The ideas we present here are not bound to any particular programming language, giving rise to a method of wide applicability.Peer ReviewedPostprint (published version

Inducing metaassociations and induced relationships

In the last years, UML has been tailored to be used as a domainspecific modelling notation in several contexts. Extending UML with this purpose entails several advantages: the integration of the domain in a standard framework; its potential usage by the software engineering community; and the existence of supporting tools. In previous work, we explored one particular issue of heavyweight extensions, namely, the definition of inducing metaassociations in metamodels as a way to induce the presence of specific relationships in their instances. Those relationships were intended by the metamodel specifier but not forced by the metamodel itself. However, our work was restricted to the case of induced associations. This paper proposes an extension to the general case in which inducing metaassociations may force the existence of arbitrary relationships at M1. To attain this goal, we provide a general definition of inducing metaassociation that covers all the possible cases. After revisiting induced associations, we show the inducement of the other relationship types defined in UML: association classes, generalization and dependencies.Peer ReviewedPostprint (author’s final draft

Smelling Nano Aerial Vehicle for Gas Source Localization and Mapping

This paper describes the development and validation of the currently smallest aerial platform with olfaction capabilities. The developed Smelling Nano Aerial Vehicle (SNAV) is based on a lightweight commercial nano-quadcopter (27 g) equipped with a custom gas sensing board that can host up to two in situ metal oxide semiconductor (MOX) gas sensors. Due to its small form-factor, the SNAV is not a hazard for humans, enabling its use in public areas or inside buildings. It can autonomously carry out gas sensing missions of hazardous environments inaccessible to terrestrial robots and bigger drones, for example searching for victims and hazardous gas leaks inside pockets that form within the wreckage of collapsed buildings in the aftermath of an earthquake or explosion. The first contribution of this work is assessing the impact of the nano-propellers on the MOX sensor signals at different distances to a gas source. A second contribution is adapting the 'bout' detection algorithm, proposed by Schmuker et al. (2016) to extract specific features from the derivative of the MOX sensor response, for real-time operation. The third and main contribution is the experimental validation of the SNAV for gas source localization (GSL) and mapping in a large indoor environment (160 m²) with a gas source placed in challenging positions for the drone, for example hidden in the ceiling of the room or inside a power outlet box. Two GSL strategies are compared, one based on the instantaneous gas sensor response and the other one based on the bout frequency. From the measurements collected (in motion) along a predefined sweeping path we built (in less than 3 min) a 3D map of the gas distribution and identified the most likely source location. Using the bout frequency yielded on average a higher localization accuracy than using the instantaneous gas sensor response (1.38 m versus 2.05 m error), however accurate tuning of an additional parameter (the noise threshold) is required in the former case. The main conclusion of this paper is that a nano-drone has the potential to perform gas sensing tasks in complex environments

Interaction of silver-lignin nanoparticles with mammalian mimetic membranes

Silver nanoparticles (AgNPs) have broad spectrum antibacterial activity, but their toxicity to human cells has raised concerns related to their use as disinfectants or coatings of medically relevant surfaces. To address this issue, NPs comprising intrinsically bactericidal and biocompatible biopolymer and Ag with high antibacterial efficacy against common pathogens and compatibility to human cells have been engineered. However, the reason for their lower toxicity compared to AgNPs has not yet been elucidated. This work studies the in vitro interaction of AgLNPs with model mammalian membranes through two approaches: (i) Langmuir films and (ii) supported planar bilayers studied by quartz crystal microbalance and atomic force spectroscopy. These approaches elucidate the interactions of AgLNPs with the model membranes indicating a prominent effect of the bioresourced lignin to facilitate the binding of AgLNPs to the mammalian membrane, without penetrating through it. This study opens a new avenue for engineering of hybrid antimicrobial biopolymer – Ag or other metal NPs with improved bactericidal effect whereas maintaining good biocompatibilityPeer ReviewedPostprint (published version

Biomimetic monolayer films of digalactosyldiacylglycerol incorporating plastoquinone

The photosynthesis is the process used by plants and bacteria cells to convert inorganic matter in organic thanks to the light energy. This process consist on several steps, being one of them the electronic transport from the photosystem II to the cytochrome thanks to plastoquinone-9 (PQ). Here we prepare membranes that mimic the characteristics and composition of natural photosynthetic cell membranes and we characterize them in order to obtain the PQ molecules position in the membrane and their electrochemical behaviour. The selected galactolipid is digalactosyldiacylglycerol (DGDG) that represents the 30% of the thylakoid membrane lipid content. The results obtained are worthful for several science fields due to the relevance of galactolipids as anti-algal, anti-viral, anti-tumor and anti-inflammatory agents and the antioxidant and free radical scavenger properties of prenylquinones.; Both pure components (DGDG and PQ) and the DGDG:PQ mixtures have been studied using surface pressure-area isotherms. These isotherms give information about the film stability and indicate the thermodynamic behaviour of the mixture and their physical state. The Langmuir-Blodgett (LB) film has been transferred forming a monolayer that mimics the bottom layer of the biological membranes. This monolayer on mica has been topo-graphically characterized using AFM and both the height and the physical state that they present have been obtained. Moreover, these monolayers have been transferred onto ITO that is a hydrophilic substrate with good optical and electrical features, so that, it is suitable for studying the electrochemical behaviour of these systems and it is a good candidate for energy producing devices. (C) 2015 Elsevier B.V. All rights reserved.Peer ReviewedPostprint (author’s final draft