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This paper investigates the dynamic response problem of an orthotropic rectangular membrane structure excited by the heavy rainfall. Firstly, a determined model is proposed to express the load of heavy rainfall imposed on the membrane structure. Then, the geometrically nonlinear governing motion equations of the membrane structure are established based on the von Kármán's theory, and solved by the perturbation method. Consequently, the approximated analytical solution of displacement can be obtained. Secondly, the experimental study of this dynamic response problem is carried out. The theoretical model is validated by the experimental data based on the developed artificial simulated rainfall impact system. Moreover, the effects of adding weight from the accumulated rain on structural characteristics are analyzed. Additionally, the parameter discussions varying with rainfall intensity, material properties, pre-tension, structural size, and inclined angle are made in detail. This work provides a reliable theoretical model and experimental system to study the dynamic response problem of membrane structures excited by heavy rainfall and the guidance for the dynamic design, construction and maintenance of membrane structures in practical engineering as well. [ABSTRACT FROM AUTHOR]

Highlights • New method for obtaining higher orders of diffraction. • Higher resolution low-angle x-ray data for DPPC gel phase. • Direct structural evidence for mini-interdigitation of hydrocarbon chains in the bilayer center. • Improved modeling of low angle data to provide electron density profiles and component probabilities. Abstract High resolution low angle x-ray data are reported for the gel phase of DPPC lipid bilayers, extending the previous q range of 1.0 Å−1 to 1.3 Å−1, and employing a new technique to obtain more accurate intensities and form factors |F(q)| for the highest orders of diffraction. Combined with previous wide angle x-ray and volumetric data, a space filling model is employed to obtain gel phase structure at a mesoscopic level. This analysis provides direct evidence that the hydrocarbon chains from opposing monolayers are mini-interdigitated, consistent with the previously well-established result that the opposing monolayers are strongly coupled with respect to their chain tilt directions. Even more detailed structural features are described that have not been obtained from experiment but that could, in principle, be obtained from simulations that would first be validated by agreement with the wide angle and the new low angle |F(q)| x-ray data. [ABSTRACT FROM AUTHOR]

Highlights • Memtein is coined to describe a membrane protein bound to a layer of biologically relevant, structured lipids. • Devolopment of styrene maleic acid lipid particle (SMALP) technology to prepare native nanodiscs reviewed. • Impact of SMALP and related methods on structural biology and memtein research is explored. Abstract The concept of a memtein as the minimal unit of membrane function is proposed here, and refers to the complex of a membrane protein together with a continuous layer of biological lipid molecules. The elucidation of the atomic resolution structures and specific interactions within memteins remains technically challenging. Nonetheless, we argue that these entities are critical endpoints for the postgenomic era, being essential units of cellular function that mediate signal transduction and trafficking. Their biological mechanisms and molecular compositions can be resolved using native nanodiscs formed by poly(styrene-co-maleic acid) (SMA) copolymers. These amphipathic polymers rapidly and spontaneously fragment membranes into water-soluble discs holding a section of bilayer. This allows structures of complexes found in vivo to be prepared without resorting to synthetic detergents or artificial lipids. The ex situ structures of memteins can be resolved by methods including cryo-electron microscopy (cEM), X-ray crystallography (XRC), NMR spectroscopy and mass spectrometry (MS). Progress in the field demonstrates that memteins are better representations of how biology actually works in membranes than naked proteins devoid of lipid, spurring on further advances in polymer chemistry to resolve their details. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • DHA readily incorporates into DPPC liposomes, localizing at the lipid headgroup region. • DHA increases DPPC membrane fluidity. • DHA induces changes in the lipid bilayer structure Abstract Docosahexaenoic acid (DHA, 22:6) is a natural active compound that has raised considerable interest due to its several biological effects. In this work, effects of free DHA on the physicochemical properties of dipalmitoylphosphatidylcholine (DPPC) liposomes are investigated in terms of lipid membrane structure, by means of temperature-dependent zeta potential measurements, density studies and molecular dynamics simulations. Experimental results predict, in good agreement with simulations that DHA readily incorporates into DPPC liposomes, localizing at the lipid headgroup region. These data show that DHA induces changes in the lipid bilayer structure as well as in membrane fluidity. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Pulmonary vein cardiomyocytes possess T-tubules. • Ryanodine receptors were distributed as striations and along cell periphery. • Asynchronous spontaneous Ca2+ transients present between those that were electrically evoked. • Raising extracellular Ca2+ concentration increased frequency of spontaneous Ca2+ transients. • The wave velocity and synchronisation of spontaneous Ca2+ transients was also increased. Abstract The pulmonary veins have an external sleeve of cardiomyocytes that are a widely recognised source of ectopic electrical activity that can lead to atrial fibrillation. Although the mechanisms behind this activity are currently unknown, changes in intracellular calcium (Ca2+) signalling are purported to play a role. Therefore, the intracellular Ca2+ concentration was monitored in the pulmonary vein using fluo-4 and epifluorescence microscopy. Electrical field stimulation evoked a synchronous rise in Ca2+ in neighbouring cardiomyocytes; asynchronous spontaneous Ca2+ transients between electrical stimuli were also present. Immediately following termination of electrical field stimulation at 3 Hz or greater, the frequency of the spontaneous Ca2+ transients was increased from 0.45 ± 0.06 Hz under basal conditions to between 0.59 ± 0.05 and 0.65 ± 0.06 Hz (P < 0.001). Increasing the extracellular Ca2+ concentration enhanced this effect, with the frequency of spontaneous Ca2+ transients increasing from 0.45 ± 0.05 Hz to between 0.75 ± 0.06 and 0.94 ± 0.09 Hz after electrical stimulation at 3 to 9 Hz (P < 0.001), and this was accompanied by a significant increase in the velocity of Ca2+ transients that manifested as waves. Moreover, in the presence of high extracellular Ca2+, the spontaneous Ca2+ transients occurred more synchronously in the initial few seconds following electrical stimulation. The ryanodine receptors, which are the source of spontaneous Ca2+ transients in pulmonary vein cardiomyocytes, were found to be arranged in a striated pattern in the cell interior, as well as along the periphery of cell. Furthermore, labelling the sarcolemma with di-4-ANEPPS showed that over 90% of pulmonary vein cardiomyocytes possessed T-tubules. These findings demonstrate that the frequency of spontaneous Ca2+ transients in the rat pulmonary vein are increased following higher rates of electrical stimulation and increasing the extracellular Ca2+ concentration. [ABSTRACT FROM AUTHOR]

The mechanism of action of brassinosteroids (BRs) in plant cells under stress has not been fully explained, despite ample evidence of their protective effects. The aim of this study was to investigate the significance of physicochemical properties of cell membranes during an interaction with BRs under stress conditions induced by a mycotoxin zearalenone (ZEA). Experiments were performed in in vitro cultures of wheat cells obtained from immature embryos of tolerant and sensitive genotypes. ZEA added to media (30 µM) accumulated in greater amounts in the cells of sensitive wheat, contrary to BRs, which accumulated in greater amounts by the tolerant genotype when added to media at 0.1 µM. Incorporation of 24-epibrassinolide (EBR) stimulated synthesis of casta- and homocastasterone, that is, endogenous BRs present in wheat cells, and enhanced the content of homocastasterone. When the cultures were supplemented with the mixture of ZEA and EBR, castasterone synthesis was stimulated to a higher degree in cells of the sensitive plant. EBR and ZEA added separately activated antioxidant enzyme systems in both genotypes but with preference for the sensitive one. In the cells treated with ZEA + EBR, the activation was close to that observed for EBR alone. The study discussed also the role of membrane permeability, electrokinetic potential changes, and structural properties of native (plasmalemma) and model (DOPC) monolayers in the mechanism of EBR-induced protection, including the possibility of replacing ZEA absorbed in the membrane lipid layers by BR molecules, independently of the activation of the antioxidant system. [ABSTRACT FROM AUTHOR]

Abstract We report small angle X-ray scattering (SAXS) data from large unilamellar vesicles as model membranes composed of 1-palmitoyl-2-oleoyl- sn -glycero-3-phosphocoline (POPC) and two oxidized species, namely its hydroperoxidized form POPC-OOH and 1-palmitoyl-2-azelaoyl- sn -glycero-3-phosphocholine (PazePC) lipid that has a carboxyl group at the end of its truncated sn -2 chain. The replacement of POPC by either POPC-OOH (POPC-OOH x POPC 1− x) or PazePC (PazePC x POPC 1− x), with oxidized lipid molar ratio x varying from 0.00 up to 1.00, permits to experimentally inspect changes in the membrane structural properties due to oxidation. The volume fraction distribution of each lipid chemical group along the bilayer is determined. The results quantify that 95% of the hydroperoxide group lies in the membrane polar moiety, near the carbonyl and phosphate groups, whereas just 5% of OOH group experiences the polar/apolar interface, for all values of x studied. In the case of PazePC up to x = 0.33, a bimodal distribution of the carboxyl group in the interior and polar regions of the lipid membrane is obtained, probably due to a dynamic movement of the shortened alkyl chain towards the water interface. The mean molecular area A gradually increases from 65.4 ± 0.4 Å2 for POPC bilayers to 78 ± 2 Å2 for pure POPC-OOH bilayers, whereas POPC-OOH membrane thickness resulted to be 20% thinner than the non-oxidized POPC membrane. For PazePC up to x = 0.33, A increases to 67 ± 2 Å2 with 10% of membrane thinning. The SAXS results thus demonstrate how the lipid oxidation progress affects the membrane structural features, thus paving the way to better understand membrane damage under oxidative stress. Graphical Abstract Highlights • The hydroperoxide group is preferentially located near the polar/apolar interface. • Significant fraction of the COOH group is located in the middle of the apolar region. • Increased membrane surface area due to the inclusion of oxidized lipid • Decreased membrane thickness due to the presence of oxidized lipid [ABSTRACT FROM AUTHOR]

In order to obtain the separation membranes possessing outstanding water permeability and mechanical property, poly (vinylidene fluoride) (PVDF) flat sheet membranes were fabricated via the low-temperature thermally induced phase separation method (L-TIPS) by the ternary system of PVDF/dibutyl phthalate (DBP)/dioctyl phthalate (DOP). The effects of PVDF concentration, the concentration ratio of diluent mixtures, cooling rate and coagulation bath temperature on membrane structures and performance were studied. The results showed that with the increases of PVDF and DOP concentration, the spherulite structure of the membrane was gradually transformed into a bicontinuous structure. The pure water flux and porosity of membrane decreased, but the tensile strength and elongation at break of membrane increased with the increase of PVDF. When the coagulation bath temperature and the casting solution temperature were similar, and the cooling rate was slowed down, the pure water flux and the average pore size of the membrane increased, while the porosity is almost unchanged. Therefore, when the mass fraction of PVDF was 40% in the casting solution and the casting solution system was cooled under the condition of 20 °C air bath cooling and 60 °C of coagulation bath temperature, the separation membranes were prepared which possessed good water permeability and the fine mechanical property, the pure water flux was 325.65 L/(m²⋅h) and the tensile strength could reach 1.80 MPa. [ABSTRACT FROM AUTHOR]

Ladderane lipids are unique to anaerobic ammonium-oxidizing (anammox) bacteria and are enriched in the membrane of the anammoxosome, an organelle thought to compartmentalize the anammox process, which involves the toxic intermediate hydrazine (N2H4). Due to the slow growth rate of anammox bacteria and difficulty of isolating pure ladderane lipids, experimental evidence of the biological function of ladderanes is lacking. We have synthesized two natural and one unnatural ladderane phosphatidylcholine lipids and compared their thermotropic properties in self-assembled bilayers to distinguish between [3]- and [5]-ladderane function. We developed a hydrazine transmembrane diffusion assay using a water-soluble derivative of a hydrazine sensor and determined that ladderane membranes are as permeable to hydrazine as straight-chain lipid bilayers. However, pH equilibration across ladderane membranes occurs 5-10 times more slowly than across straight-chain lipid membranes. Langmuir monolayer analysis and the rates of fluorescence recovery after photobleaching suggest that dense ladderane packing may preclude formation of proton/hydroxide-conducting water wires. These data support the hypothesis that ladderanes prevent the breakdown of the proton motive force rather than blocking hydrazine transmembrane diffusion in anammox bacteria. [ABSTRACT FROM AUTHOR]

Cardiolipins have multiple vital functions within biological cell membranes, most notably in the energy metabolism associated with the inner mitochondrial membrane. Considering their essential role, peroxidation of cardiolipins may plausibly have significant effects, as peroxidation is known to alter the functionality of lipid molecules. We used atomistic molecular dynamics simulations to study how peroxidation of cardiolipin affects the properties of the inner mitochondrial membrane. To this end, we explored what happens when varying fractions of fatty acid chains of cardiolipin are replaced by its four different oxidized products in systems modeling the inner mitochondrial membrane. We found that the oxidation of cardiolipin leads to a conformational change both in the backbone/head group and in chain regions of oxidized cardiolipin molecules. The oxidized groups were observed to shift closer to the membrane–water interface region, where they formed hydrogen bonds with several other groups. Additionally, the conformational change turned out to decrease bilayer thickness, and to increase the area per lipid chain, though these changes were minor. The acyl chain conformational order of unoxidized lipids exposed to interactions with oxidized cardiolipins was increased in carbons 3–5 and decreased in carbons 13–17 due to the structural reorganization of the cardiolipin molecules. Overall, the results bring up that the conformation of cardiolipin is altered upon oxidation, suggesting that its oxidation may interfere its interactions with mitochondrial proteins and thereby affect cardiolipin-dependent cellular processes such as electron and proton transport. [ABSTRACT FROM AUTHOR]

This paper studies active control of large-amplitude vibration of a membrane structure with piezoelectric actuators. First, dynamic equation of large-amplitude vibration of the membrane structure is established based on the von Karman’s large deformation assumption. Next, a four-mode nonlinear model is obtained by applying Galerkin decomposition to the nonlinear dynamic equation. Then, a model reference adaptive controller is designed to suppress the large-amplitude vibration of the membrane structure, and the stability of the controller is proven by Lyapunov’s stability theory. Finally, numerical simulations are carried out to verify the validity of the studies in this paper. Simulation results indicate that the model reference adaptive controller given in this paper can suppress the large-amplitude vibration of the membrane structure effectively; this adaptive controller is robust to modeling errors, and it is also more robust than the classical velocity feedback controller in the presence of actuator disturbance and sensor disturbance. [ABSTRACT FROM AUTHOR]

Abstract: Digital form‐fitting – Cog connections for complex steel structures. This paper discusses the potentials of form‐fit connections in steel structures to generate ‘digital details' which are easily adapted to different boundary conditions and organize their manufacturing and assembly. In this paper, a grid shell for a 45 m span ETFE cushion dome and a large membrane façade that use digital detailing as a basic principle for all joints of the structure, will be discussed. The projects demonstrate how the inclusion of simple digital production processes in the detail design enable rational planning, manufacturing and assembly of complex structures. Next to the new challenge in understanding geometric relationships, material properties, and manufacturing techniques, computationally expensive analysis using Finite Volume Elements with nonlinear connection and material models is necessary to the engineering of such details. [ABSTRACT FROM AUTHOR]

Snow drifting driven by wind will cause unevenly distributed snow on roofs, which may result in the collapse of structures, sometimes even devastating disaster. Long-span structures are more sensitive to unevenly distributed snow loads, especially for tension membrane structures. Thus, an accurate prediction of snow distribution on roof surface is vital to structural design. A numerical simulation method for snowdrift is presented in this study. Based on Euler-Euler method in multi-phase flow theory, this numerical model adopt Mixture model by employing commercial computational fluid dynamics (CFD) software FLUENT, combined with the snow deposition and erosion model, the snow distribution can be obtained. The performance of this numerical model is examined and verified against data form field measurement carried out in previous literature. Then the snowdrift on a long-span membrane roof is simulated, the snow shape factor is given under different wind directions to estimate the worst load case. Furthermore, the mechanical performance of the membrane structure under snow load is studied. The unevenly distributed snow simulated by CFD is applied on the membrane roof, for comparison a uniform snow load case is also considered. The results of finite element analysis (FEA) show that non-uniform snow load is more dangerous and should be considered. [ABSTRACT FROM AUTHOR]

This paper studies the aerodynamic stability of a tensioned, geometrically nonlinear orthotropic membrane structure with hyperbolic paraboloid in sag direction. Considering flow separation, the wind field around membrane structure is simulated as the superposition of a unifonn flow and a continuous vortex layer. By the potential flow theory in fluid mechanics and the thin airfoil theory in aerodynamics, aerodynamic pressure acting on membrane surface can be determined. And based on the large amplitude theory of membrane and D'Alembert's principle, interaction governing equations of wind-structure are established. Then, under the circumstance of single-mode response, the Bubnov-Galerkin approximate method is applied to transform the complicated interaction governing equations into a system of second-order nonlinear differential equation with constant coefficients. Through judging the frequency characteristic of the system characteristic equation, the critical velocity of divergence instability is determined. Different parameter analysis shows that the orthotropy, geometrical nonlinearity and scantling of structure is significant for preventing destructive aerodynamic instability in membrane structures. Compared to the model without considering flow separation, it's basically consistent about the divergence instability regularities in the flow separation model. [ABSTRACT FROM AUTHOR]

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) differentially influence lipid oxidation, signal transduction, fluidity, and cholesterol domain formation, potentially due in part to distinct membrane interactions. We used small angle X-ray diffraction to evaluate the EPA and DHA effects on membrane structure. Membrane vesicles composed of 1-palmitoyl-2-oleoyl- sn -glycero-3-phosphocholine (POPC) and cholesterol (C) (0.3C:POPC mole ratio) were prepared and treated with vehicle, EPA, or DHA (1:10 mol ratio to POPC). Electron density profiles generated from the diffraction data showed that EPA increased membrane hydrocarbon core electron density over a broad area, up to ± 20 Å from the membrane center, indicating an energetically favorable extended orientation for EPA likely stabilized by van der Waals interactions. By contrast, DHA increased electron density in the phospholipid head group region starting at ± 12 Å from the membrane center, presumably due to DHA-surface interactions, with coincident reduction in electron density in the membrane hydrocarbon core centered ± 7–9 Å from the membrane center. The membrane width ( d -space) decreased by 5 Å in the presence of vehicle as the temperature increased from 10 °C to 30 °C due to increased acyl chain trans-gauche isomerizations, which was unaffected by addition of EPA or DHA. The influence of DHA on membrane structure was modulated by temperature changes while the interactions of EPA were unaffected. The contrasting EPA and DHA effects on membrane structure indicate distinct molecular locations and orientations that may contribute to observed differences in biological activity. [ABSTRACT FROM AUTHOR]

Polynoid worm elytra emit light when mechanically or electrically stimulated. Specialized cells, the photocytes, contain light emitting machineries, the photosomes. Successive stimulations induce light intensity variations and show a coupling within and between photosomes. Here, we describe, using electron tomography of cryo-substituted elytra and freeze-fracturing, the structural transition associated to light emission: undulating tubules come closer, organize and their number forming photosomes increases. Two repeating undulating tubules in opposite phase compose the photosome. Undulations are located on three hexagonal layers that regularly repeat and are equally displaced, in x y and z. The tubule membranes within layers merge giving rise to rings that tend to obey to quasi-rhombohedral symmetry. Merging may result either from close-association, hemifusion (one leaflet fusion) or from fusion (two leaflets fusion). Although the resolution of tomograms is not sufficient to distinguish these three cases, freeze-fracturing shows that hemifusion is a frequent process that leads to an reversible anastomosed membrane complex favoring communications, appearing as a major coupling factor of photosome light emission. [ABSTRACT FROM AUTHOR]

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The aminated graphene oxide (GO) was prepared by the functionalization of pristine GO with ethylenediamine and then dispersed into the poly(amic acid) (the precursor of polyimide [PI]) solution followed by the chemical imidization to successfully fabricate the PI/amine-functionalized GO mixed matrix membranes (MMMs) using in-situ polymerization method. Chemical structure and morphology of the GO before and after amine modification were characterized by scanning electron microscopy, Raman spectrum, Fourier transform infrared, and X-ray photoelectron spectroscopy. Scanning electron microscopy indicated that fine dispersion of GO throughout PI matrix was achieved, which indicates that the in-situ polymerization approach can enhance the interfacial interaction between the GO and the PI matrix, and then improve the dispersion of carbon material in the polymer matrix. Compared with the conventional solution mixture method, the MMMs prepared with in-situ polymerization method showed excellent CO2 permeability and CO2/N2 selectivity. The MMMs doped with 3 wt.% aminated GO exhibited maximum gas separation performance with a CO2 permeability of 12.34 Barrer and a CO2/N2 selectivity of 38.56. These results suggest that the amino groups on GO have strong interaction with the CO2 molecules, which can significantly increase the solubility of polar gas. Our results provide an easy and efficient way to prepare MMMs with good mechanical behavior and excellent gas separation performance. [ABSTRACT FROM AUTHOR]

A deployable structure serves an important function in small satellites as their performance is improved steadily. Larger deployable solar array paddles are expected as the satellite requires a larger amount of electric power. The synthetic aperture radar (SAR) system for small satellites requires a deployable antenna. Various deployable membrane structures have been proposed for the deorbit of micro/nanosatellites in low Earth orbit. The actuators and devices for a deployable structure continue to progress along with the development of a deployable structure. The hold-release mechanism has been becoming smaller and simpler. The shape control devices are actively researched for a high-precision deployable structure. There are several requirements imposed on the deployable structures, e.g., low cost, lightweight, small volume in stored configuration, reliable deployment, large aperture in deployed configuration, and accuracy/repeatability of a deployed shape. Dedicated efforts are made to satisfy these requirements in research and development of a deployable structure/device. This paper provides an overview of the past and current research and development of a deployable structure for small satellites. [ABSTRACT FROM PUBLISHER]

The ability of antifreeze proteins (AFP's) and glycoproteins (AFGP's) to prevent damage to certain organisms under cold stress is well established. These molecules have also been shown to prevent chilling damage in some biological membranes and interaction between membranes and AF(G)P's has been observed during chilling events; however, the exact mechanism of membrane stabilization is still not well understood. Molecular modelling is an ideal technique for probing atomistic information in these systems although modelling studies to date have focused on peptide structure and the site and mode, e.g. , insertion, of the peptide-membrane interaction. To provide insight into how AF(G)P's may act to stabilize (or destabilize) membranes during phase transitions, we have conducted molecular dynamics (MD) simulations of a solvated dimyristoylphosphatidylcholine (DMPC) lipid bilayer containing an AFP Type I at the lipid/water interface at several temperatures. We present the analysis of several properties of the phospholipid bilayer that are relevant when considering phase transitions. Possible areas for concentrating future research efforts have been highlighted; namely the acyl chain order and the polar headgroups, both of which have been implicated in experimental studies of the stabilization of model membranes by AF(G)P's. • Molecular dynamics simulations of an antifreeze peptide present at the water / lipid interface of a model membrane. • Analysis of several properties of the phospholipid bilayer relevant when considering phase transitions are presented. • Results indicate acyl chain order and polar head-group positioning are influenced by the presence of an antifreeze peptide. • Investigation of stabilization of a solvated model DMPC lipid bilayer. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) have been emerged as a versatile class of compounds that can be easily tuned to achieve desirable properties for various applications. The ability of ILs to interact with biomembranes has attracted significant interest, as they have been shown to modulate membrane properties in ways that may have implications for various biological processes. This review provides an overview of recent studies that have investigated the interaction between ILs and biomembranes. We discuss the effects of ILs on the physical and chemical properties of biomembranes, including changes in membrane fluidity, permeability, and stability. We also explore the mechanisms underlying the interaction of ILs with biomembranes, such as electrostatic interactions, hydrogen bonding, and van der Waals forces. Additionally, we discuss the future prospects of this field. [Display omitted] • Interaction of ionic liquids with cellular membrane is favourable due to enhanced system entropy and reduced free energy. • Ionic liquids perturb the self-assembly of lipids in a cellular membrane. • Ionic liquids modify the mechano-elasticity of a cellular membrane. • Dynamics of lipids in a membrane at the presence of ionic liquids are altered. [ABSTRACT FROM AUTHOR]

The saturated LPC18:0 and unsaturated LPC18:1 lysophosphatidylcholines have important roles in inflammation and immunity and are interesting targets for immunotherapy. The synthetic cationic lipid DODAB has been successfully employed in delivery systems, and would be a suitable carrier for those lysophosphatidylcholines. Here, assemblies of DODAB and LPC18:0 or LPC18:1 were characterized by Differential Scanning Calorimetry (DSC) and Electron Paramagnetic Resonance (EPR) spectroscopy. LPC18:0 increased the DODAB gel-fluid transition enthalpy and rigidified both phases. In contrast, LPC18:1 caused a decrease in the DODAB gel-fluid transition temperature and cooperativity, associated with two populations with distinct rigidities in the gel phase. In the fluid phase, LPC18:1 increased the surface order but, differently from LPC18:0, did not affect viscosity at the membrane core. The impact of the different acyl chains of LPC18:0 and 18:1 on structure and thermotropic behavior should be considered when developing applications using mixed DODAB membranes. [Display omitted] • DODAB vesicle structure can be modulated by lysophosphatidylcholine acyl chain. • Saturated lysophosphatidylcholine rigidified the gel phase of cationic membranes. • Unsaturated lysophosphatidylcholine destabilized the gel phase. • Saturated lysophosphatidylcholine rigidified the fluid phase of cationic membranes. • Unsaturated lysophosphatidylcholine rigidified the surface of the fluid phase. [ABSTRACT FROM AUTHOR]