The enzymatic sphingomyelin to ceramide conversion increases the shear membrane viscosity at the air-water interface

Whereas most of lipids have viscous properties and they do not have significant elastic features, ceramides behave as very rigid solid assemblies, displaying viscoelastic behaviour at physiological temperatures. The present review addresses the surface rheology of lipid binary mixtures made of sphingomyelin and ceramide. However, ceramide is formed by the enzymatic cleavage of sphingomyelin in cell plasma membranes. The consequences of the enzymatically-driven ceramide formation involve mechanical alterations of the embedding membrane. Here, an increase on surface shear viscosity was evidenced upon enzymatic incubation of sphingomyelin monolayers. The overall rheological data are discussed in terms of the current knowledge of the thermotropic behaviour of ceramide-containing model membranes

Extracción con líquidos presurizados para la obtención de fracciones antioxidantes y anti-inflamatorias a partir de la microalga Isochrysis galbana

Trabajo presentado a las I Jornadas Científicas del CIAL celebradas el 5 de junio de 2014 en Madrid.Las microalgas son consideradas como una fuente innovadora para el desarrollo de nuevos productos alimentarios y farmacéuticos debido a su alto contenido en moléculas de alto interés biológico, como ácidos grasos, carotenoides, vitaminas, esteroles, polisacáridos y compuestos fenólicos. Este contenido en moléculas bioactivas se ha relacionado con efectos funcionales beneficiosos para la salud, como consecuencia, por ejemplo, de su efecto antioxidante y anti-inflamatorio. En los últimos años se han empleado nuevos métodos de extracción para la obtención de dichos compuestos de interés mediante tecnologías medioambientalmente limpias, entre las que cabe destacar la extracción con líquidos presurizados (PLE). En este trabajo se ha llevado a cabo la extracción de la fracción fenólica de la microalga Isochrysis galbana mediante PLE. Para obtener un extracto de alto contenido en compuestos fenólicos, se realizó un diseño experimental (3^2) estudiando el efecto de la temperatura y el porcentaje de etanol en el disolvente, factores influyentes en el proceso de extracción PLE. Las variables respuesta fueron rendimiento de extracción (%), contenido de fenoles totales y actividad antioxidante. Por último, se llevo a cabo la extracción PLE con las condiciones optimizadas marcadas por el diseño experimental para la obtención de un extracto rico en compuestos fenólicos. Los extractos obtenidos se caracterizaron funcionalmente en términos de actividad anitioxidante y actividad anti-inflamatoria.M.H. agradece al MICINN su contrato de investigación “Ramón y Cajal”. I.L-E. agradece al CSIC por su contrato JAE-DOC. Los autores agradecen la financiación del proyecto “MIRACLES - Multi-product Integrated bioRefinery of Algae: from Carbon dioxide and Light Energy to high-value Specialties (KBBE-613588)”.Peer reviewe

Direct Cytoskeleton Forces Cause Membrane Softening in Red Blood Cells

Erythrocytes are flexible cells specialized in the systemic transport of oxygen in vertebrates. This physiological function is connected to their outstanding ability to deform in passing through narrow capillaries. In recent years, there has been an influx of experimental evidence of enhanced cell-shape fluctuations related to metabolically driven activity of the erythroid membrane skeleton. However, no direct observation of the active cytoskeleton forces has yet been reported to our knowledge. Here, we show experimental evidence of the presence of temporally correlated forces superposed over the thermal fluctuations of the erythrocyte membrane. These forces are ATP-dependent and drive enhanced flickering motions in human erythrocytes. Theoretical analyses provide support for a direct force exerted on the membrane by the cytoskeleton nodes as pulses of well-defined average duration. In addition, such metabolically regulated active forces cause global membrane softening, a mechanical attribute related to the functional erythroid deformability

Wind field simulation with isogeometric analysis

[EN]For wind field simulation with isogeometric analysis, firstly it is necessary to generate a spline parameterization of the computational domain, which is an air layer above the terrain surface. This parameterization is created with the meccano method from a digital terrain model. The main steps of the meccano method for tetrahedral mesh generation were introduced in [1, 2]. Based on the volume parameterization obtained by the method, we can generate a mapping from the parametric T-mesh to the physical space [3, 4]. Then, this volumetric parameterization is used to generate a cubic spline representation of the physical domain for the application of isogeometric analysis. We consider a mass-consistent model [5] to compute the wind field simulation in the three-dimensional domain from wind measurements or a wind forecasted by a meteorological model (for example, WRF or HARMONIE). From these data, an interpolated wind field is constructed. The mass-consistent model obtains a new wind field approaching the interpolated one, but verifying the continuity equation (mass conservation) for constant density and the impermeabilitycondition on the terrain. This adjusting problem is solved by introducing a Lagrange multiplier, that is the solution of a Poisson problem. The resulting field is obtained from the interpolated one and the gradient of the Lagrange multiplier. It is well known that if we use classical Lagrange finite elements, the gradient of the numerical solution is discontinuous over the element boundary. The advantage of using isogeometric analysis with cubic polynomial basis functions [6, 7] is that we obtain a C2 continuity for the Lagrange multiplier in the whole domain. In consequence, the resulting wind field is better approximated. Applications of the proposed technique are presented.Ministerio de Economía y Competitividad del Gobierno de España; Fondos FEDER; CONACYT-SENE

Nonequilibrium fluctuations of lipid membranes by the rotating motor protein F1F0-ATP synthase

ATP synthase is a rotating membrane protein that synthesizes ATP through proton-pumping activity across the membrane. To unveil the mechanical impact of this molecular active pump on the bending properties of its lipid environment, we have functionally reconstituted the ATP synthase in giant unilamellar vesicles and tracked the membrane fluctuations by means of flickering spectroscopy. We find that ATP synthase rotates at a frequency of about 20 Hz, promoting large nonequilibrium deformations at discrete hot spots in lipid vesicles and thus inducing an overall membrane softening. The enhanced nonequilibrium fluctuations are compatible with an accumulation of active proteins at highly curved membrane sites through a curvature−protein coupling mechanism that supports the emergence of collective effects of rotating ATP synthases in lipid membranes

Accumulated bending energy elicits neutral sphingomyelinase activity in human red blood cells

We propose that accumulated membrane bending energy elicits a neutral sphingomyelinase (SMase) activity in human erythrocytes. Membrane bending was achieved by osmotic or chemical processes, and SMase activity was assessed by quantitative thin-layer chromatography, high-performance liquid chromatography, and electrospray ionization-mass spectrometry. The activity induced by hypotonic stress in erythrocyte membranes had the pH dependence, ion dependence, and inhibitor sensitivity of mammalian neutral SMases. The activity caused a decrease in SM contents, with a minimum at 6 min after onset of the hypotonic conditions, and then the SM contents were recovered. We also elicited SMase activity by adding lysophosphatidylcholine externally or by generating it with phospholipase A 2. The same effect was observed upon addition of chlorpromazine or sodium deoxycholate at concentrations below the critical micellar concentration, and even under hypertonic conditions. A unifying factor of the various agents that elicit this SMase activity is the accumulated membrane bending energy. Both hypo-and hypertonic conditions impose an increased curvature, whereas the addition of surfactants or phospholipase A 2 activation increases the outer monolayer area, thus leading to an increased bending energy. The fact that this latent SMase activity is tightly coupled to the membrane bending properties suggests that it may be related to the general phenomenon of stress-induced ceramide synthesis and apoptosis. © 2012 Biophysical Society

Mitochondrial membrane models built from native lipid extracts: Interfacial and transport properties

The mitochondrion is an essential organelle enclosed by two membranes whose functionalities depend on their very specific protein and lipid compositions. Proteins from the outer mitochondrial membrane (OMM) are specialized in mitochondrial dynamics and mitophagy, whereas proteins of the inner mitochondrial membrane (IMM) have dedicated functions in cellular respiration and apoptosis. As for lipids, the OMM is enriched in glycerophosphatidyl choline but cardiolipin is exclusively found within the IMM. Though the lipid topology and distribution of the OMM and IMM are known since more than four decades, little is known about the interfacial and dynamic properties of the IMM and OMM lipid extracts. Here we build monolayers, supported bilayers and giant unilamellar vesicles (GUVs) of native OMM and IMM lipids extracts from porcine heart. Additionally, we perform a comparative analysis on the interfacial, phase immiscibility and mechanical properties of both types of extract. Our results show that IMM lipids form more expanded and softer membranes than OMM lipids, allowing a better understanding of the physicochemical and biophysical properties of mitochondrial membranes.Fil: Schiaffarino, Olivia. Universidad Complutense de Madrid; EspañaFil: Valdivieso González, David. Hospital Universitario 12 de Octubre; España. Universidad Complutense de Madrid; EspañaFil: García Pérez, Inés M.. Universidad Complutense de Madrid; EspañaFil: Peñalva, Daniel Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones Bioquímicas de Bahía Blanca. Universidad Nacional del Sur. Instituto de Investigaciones Bioquímicas de Bahía Blanca; Argentina. Universidad Nacional del Sur; ArgentinaFil: Almendro Vedia, Víctor G.. Universidad Complutense de Madrid; España. Hospital Doce de Octubre, Madrid; EspañaFil: Natale, Paolo. Universidad Complutense de Madrid; España. Hospital Universitario 12 de Octubre; EspañaFil: López Montero, Iván. Universidad Complutense de Madrid; España. Hospital Universitario 12 de Octubre; Españ

Entorno multimedia y OpenSource para la enseñanza de la Física con material interactivo

Sección Deptal. de Farmacia Galénica y Tecnología Alimentaria (Veterinaria)Fac. de VeterinariaFALSEsubmitte

Nanomechanical properties of composite protein networks of erythroid membranes at lipid surfaces

Erythrocyte membranes have been particularly useful as a model for studies of membrane structure and mechanics. Native erythroid membranes can be electroformed as giant unilamellar vesicles (eGUVs). In the presence of ATP, the erythroid membrane proteins of eGUVs rearrange into protein networks at the microscale. Here, we present a detailed nanomechanical study of individual protein microfilaments forming the protein networks of eGUVs when spread on supporting surfaces. Using Peak Force tapping Atomic Force Microscopy (PF-AFM) in liquid environment we have obtained the mechanical maps of the composite lipid-protein networks supported on solid surface. In the absence of ATP, the protein pool was characterized by a Young’s Modulus Epool ≈ 5–15 MPa whereas the complex filaments were found softer after protein supramolecular rearrangement; Efil ≈ 0.4 MPa. The observed protein softening and reassembling could be relevant for understanding the mechanisms of cytoskeleton reorganization found in pathological erythrocytes or erythrocytes that are affected by biological agents

In-silico modeling of early-stage biofilm formation

Bacteria can form biofilms in different environmental conditions, e.g. pH, temperature, nutrients, etc. Biofilm growth, therefore, is an extremely robust process. Because of this, while biofilm growth is a complex process affected by several variables, insights into biofilm formation could be obtained by studying simple schematic models. In this manuscript, we describe a hybrid molecular dynamics and Monte Carlo model for the simulation of the early stage formation of a biofilm, to explicitly demonstrate that it is possible to account for most of the processes expected to be relevant. The simulations account for the growth and reproduction of the bacteria, for their interaction and motility, for the synthesis of extracellular polymeric substances and exopolisaccharide trails. We describe the effect of these processes on the early stage formation of biofilms, in two dimensions, and also discuss preliminary three-dimensional results