Phase state and surface topography of palmitoyl-ceramide monolayers

In cell biology (and in many biophysical) studies there is a natural tendency to consider ceramide as a highly condensed, solid-type lipid conferring rigidity and close packing to biomembranes. In the present work we advanced the understanding of the phase behavior of palmitoyl-ceramide restricted to a planar interface using Langmuir monolayers under strictly controlled and known surface packing conditions. Surface pressure-molecular area isotherms were complemented with molecular area-temperature isobars and with observations of the surface topography by Brewster Angle Microscopy. The results described herein indicate that palmitoyl-ceramide can exhibit expanded, as well as condensed phase states. Formation of three phases was found, depending on the surface pressure and temperature: a solid (1.80nm thick), a liquid-condensed (1.73nm thick, likely tilted) and a liquid-expanded (1.54nm thick) phase over the temperature range 5-62 °C. A large hysteretic behavior is observed for the S phase monolayer that may indicate high resistance to domain boundary deformation. A second (or higher) order S→LC phase transition is observed at about room temperature while a first order LC→LE transition occurs in a range of temperature encompassing the physiological one (observed above 30 °C at low surface pressure). This phase behavior broadens the view of ceramide as a type of lipid not-always-rigid but able to exhibit polymorphic properties.Fil: Fanani, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; ArgentinaFil: Maggio, Bruno. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; Argentin

The hydrophobic mismatch determines the miscibility of ceramides in lipid monolayers

The organization of lipids within membranes strongly depends on the interaction with other lipid and protein molecules. Sphingolipids comprise a structurally diverse family, the ceramides being some of the simplest members. Although small chemical modifications of ceramide structure, such as varying the N-acyl chain length, lead to a complex polymorphism of this lipid, only long acyl chain ceramides have usually been studied and their properties became a putative hallmark for all ceramides. In this work, we studied the mixing behavior of C10:0 Cer, which has the N-acyl chain shorter than that of the sphingosine acyl chain and displays an expanded to condensed phase transition at 25 mN m-1 at 24 °C, with ceramides N-acylated with longer fatty acyl chains C12:0, C14:0 and C18:0. The N-acyl chain length determined the miscibility of ceramides in Langmuir monolayers, as it was ascertained by the dependence of the mean molecular area, perpendicular dipole moment, surface topography and film thickness with the mixture composition. We found that, as the hydrophobic mismatch in ceramides increased complete miscibility, partial or complete immiscibility can occur. © 2012 Elsevier Ireland Ltd.Fil: Dupuy, Fernando Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Noa Sur. Instituto Superior de Investigaciones Biológicas. Grupo de Investigación y Desarrollo del Noroeste Argentino | Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas. Grupo de Investigación y Desarrollo del Noroeste Argentino; ArgentinaFil: Maggio, Bruno. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; Argentin

Rheological properties of a two phase lipid monolayer at the air/water interface: Effect of the composition of the mixture

Many biologically relevant monolayers show coexistence of discrete domains of a long-range ordered condensed phase dispersed in a continuous, disordered, liquid-expanded phase. In this work, we determined the viscous and elastic components of the compressibility modulus and the shear viscosity of monolayers exhibiting phase coexistence with the aim at elucidating the contribution of each phase to the observed monolayer mechanical properties. To this purpose, mixed monolayers with different proportions of distearoylphosphatidylcholine (DSPC) and dimyristoylphosphatidylcholine (DMPC) were prepared and their rheological properties were analyzed. The relationship between the phase diagram of the mixture at 10 mN m-1 and the rheological properties was studied. We found that the monolayer shear viscosity is highly dependent on the presence of domains and on the domain density. In turn, the monolayer compressibility is only influenced by the presence of domains for high domain densities. For monolayers that look homogeneous on the micrometer scale (DSPC amount lower that 23 mol %), all the analyzed rheological properties remain similar to those observed for pure DMPC monolayers, indicating that in this proportion range the DSPC molecules contribute as DMPC to the surface rheology in spite of having hydrocarbon chains four carbons longer.Fil: Wilke, Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; ArgentinaFil: Vega Mercado, Franco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; ArgentinaFil: Maggio, Bruno. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; Argentin

Sesquiterpenoids in subtribe Centaureinae (Cass.) Dumort (tribe Cardueae, Asteraceae): distribution, 13C-NMR spectral data and biological properties

Asteraceae Bercht. & J. Presl is one of the biggest and most economically important plant families. The taxonomy and phylogeny of Asteraceae is rather complex and according to the latest and most reliable taxonomic classification of Panero & Funk, based on the analysis of nine chloroplast regions, the family is divided into 12 subfamilies and 35 tribes. One of the largest tribes of Asteraceae is Cardueae Cass. with four subtribes (Carlininae, Echinopinae, Carduinae and Centaureinae) and more than 2500 species. Susanna & Garcia-Jacas have organized the genera of Centaureinae (about 800 species) into seven informal groups, which recent molecular studies have confirmed: 1. Basal genera; 2. Volutaria group; 3. Rhaponticum group; 4. Serratula group; 5. Carthamus group; 6. Crocodylium group; 7. Centaurea group. This review summarizes reports on sesquiterpenoids from the Centaureinae subtribe of the Asteraceae family, as well as the 13C NMR spectral data described in the literature. It further reviews studies concerning the biological activities of these metabolites. For this work, literature data on sesquiterpenes from the Centaureinae subtribe were retrieved with the help of the SciFinder database and other similar data banks. All entries from 1958 until the end of 2011 were considered. This review is addressed to scientists working in the metabolomics field such as chemists, botanists, etc., the spectroscopic data reported make this work a good tool for structural elucidation, the biological section gives useful information to those who wish to study the structure activity relationships

The Diterpenoids of the Genus Marrubium (Lamiaceae)

The occurrence and chemical structures of labdane diterpenoids from the genus Marrubium are reviewed and the published 13C NMR spectroscopic data for these compounds is presented. The pharmacological activities and biogenesis of these diterpenoids are also reported

Ordered-disordered domain coexistence in ternary lipid monolayers activates sphingomyelinase by clearing ceramide from the active phase

We explored the action of sphingomyelinase (SMase) on ternary monolayers containing phosphatidylcholine, sphingomyelin (SM) and dihydrocholesterol, which varied along a single tie line of phase coexistence. SMase activity exhibited a higher rate and extent of hydrolysis when the film is within the liquid-expanded (LE)/liquid-ordered (LO) coexistence range, compared to monolayers in the full LO phase. Since Alexa-SMase preferably adsorbs to the LE phase and there was no direct correlation found between enzymatic activity and domain borders, we postulate that the LE phase is the active phase for ceramide (Cer) generation. The enzymatically generated Cer was organized in different ways depending on the initial LE/LO ratio. The action of SMase in Chol-poor monolayers led to the formation of Cer-enriched domains, while in Chol-rich monolayers it resulted in the incorporation of Cer in the LO phase and the formation of new Chol- and Cer-enriched domains. The following novel mechanism is proposed to provide an explanation for the favored action of SMase on interfaces that exhibit an LE-LO phase coexistence: the LO phase sequesters the product Cer causing its depletion from the more enzyme-susceptible LE phase, thus decreasing inhibition by the reaction product. Furthermore, LO domains function as a substrate reservoir by allowing a rapid exchange of the substrate from this phase to the SM-depleted LE phase.Fil: Ale, Elisa Carmen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; ArgentinaFil: Maggio, Bruno. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Fanani, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; Argentin

Zn2+-dependent surface behavior of diacylglycerol pyrophosphate and its mixtures with phosphatidic acid at different pHs

Diacylglycerol pyrophosphate (DGPP) is a minor lipid that attenuates the phosphatidic acid (PA) signal, and also DGPP itself would be a signaling lipid. DGPP is an anionic phospholipid with a pyrophosphate group attached to diacylglycerol that was shown to respond to changes of pH, thus affecting the surface organization of DGPP and their interaction with PA. In this work, we have investigated how the presence of Zn2+, modulates the surface organization of DGPP and its interaction with PA at acid and basic pHs. Both lipids formed expanded monolayers at pH 5 and 8. At pH 5, monolayers formed by DGPP became stiffer when Zn2+was added to the subphase,  while the surface potential decreased. At this pH, Zn2+ induced a phase transition from an expanded to a condensed phase state in monolayers formed by PA. Conversely, at pH 8 the effects induced by the presence of Zn2+ on the surface behaviors of the pure lipids were smaller. Thus, the interaction of the bivalent cation with both lipids was modulated by pH and by the ionization state of the polar head-groups. Mixed monolayers of PA and DGPP showed a non-ideal behavior and were not affected by the presence of Zn2+ at pH 8. This could be explained considering that when mixed, the lipids formed a close packed monolayer that could not be further modified by the cation. Our results indicate that DGPP and PA exhibit expanded and condensed phase states depending on pH, on the proportion of each lipid in the film and on the presence of Zn2+. This may have implications for a possible role of DGPP as a signaling lipid molecule.Fil: Villasuso, Ana Laura. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Biología Molecular; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Wilke, Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; ArgentinaFil: Maggio, Bruno. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; ArgentinaFil: Machado, Estela Edelmira. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Biología Molecular; Argentin

Contribution to a Taxonomic Revision of the Sicilian Helichrysum Taxa by PCA Analysis of Their Essential-Oil Compositions

The chemical profile of the essential oils in ten populations of the genus Helichrysum Mill. (Asteraceae), collected in the loci classici of the nomenclatural types of the taxa endemic to Sicily, were analyzed. Our results confirm that the analysis of secondary metabolites can be used to fingerprint wild populations of Helichrysum, the chemical profiles being coherent with the systematic arrangement of the investigated populations in three main clusters, referring to the aggregates of H. stoechas, H. rupestre, and H. italicum, all belonging to the section Stoechadina. The correct nomenclatural designation of the investigated populations is discussed and the following two new combinations are proposed: Helichrysum preslianum subsp. compactum (Guss.) Maggio, Bruno, Guarino, Senatore & Ilardi and Helichrysum panormitanum subsp. latifolium Maggio, Bruno, Guarino, Senatore & Ilardi

Estudio de interacciones de AgNPs con monocapas de dimiristoilfosfatidilcolina

El uso de nanopartículas (NPs) sintéticas se ha incrementado enormemente en los últimos años debido a su creciente uso en aplicaciones biomédicas y en nanomedicina. Por este motivo, resulta sumamente importante el estudio de las interacciones entre NPs con membranas celulares. En muchos casos las NPs necesitan unirse, romper y penetrar la membrana celular para inducir una respuesta, lo cual depende fuertemente de su tamaño, forma, carga superficial y funcionalidad química superficial. Las NPs con dimensiones menores que 2 nm pueden penetrar en las membranas celulares mientras que para las de mayor tamaño se ha propuesto que su acción ocurre principalmente a través de alteraciones de la estructura de la membrana, lo cual puede afectar fuertemente su permeabilidad, el potencial de membrana y sus funciones principales. Dependiendo entonces de la acción propuesta para las NPs en los sistemas biológicos es imprescindible el conocimiento de su interacción con las membranas.Se planteó estudiar la adsorción de AgNPs modificadas con citrato (AgNPs–CT) y con ácido 4-mercaptobenzoico (AgNPs–MBA) en ausencia y presencia de monocapas de dimiristoilfosfatidilcolina (DMPC) e investigar la capacidad de las AgNPs–CT y AgNPs–MBA para formar monocapas de Langmuir por sí mismas y en contacto con DMPC a distintos grados de empaquetamiento.Para estudiar la interacción de AgNPs–CT y con AgNPs–MBA con un modelo de biomembrana, se evaluó la adsorción de las NPs a la interfase agua/aire y a interfases de DMPC a diferentes presiones de superficie (p), a fin de conocer si la organización bidimensional que posee el lípido en la interfase condiciona la interacción con las AgNPs.Se observó interacción con DMPC por parte de todas las AgNPs (Citratadas y con MBA). Cuando la p de DMPC fue 5mN/m, la presencia de NPs produjo un incremento en la presión de 5-7.5mN/m, lo cual indica interacción con el lípido. Cuando la presión de DMPC fue 30mN/m, las NPs no produjeron cambios en p, indicando ausencia de interacción.Por otro lado, se comparó la isoterma de Langmuir de DMPC pura con las isotermas de DMPC en las que se adsorbieron AgNPs–CT y AgNPs–MBA. La interacción de AgNPs–MBA con DMPC produce una expansión del área en toda la isoterma que es prácticamente constante y representa un incremento en el área, respecto a DMPC pura. Por su parte, la presencia de MBA en la subfase no produce cambios en el área que ocupa DMPC. Las AgNPs–CT producen una pequeña modificación en el área que ocupa DMPC (respecto a cuando está pura) hasta aproximadamente 20mN/m, luego las isotermas prácticamente se superponen indicando que las NPs que estaban en la interfase son excluídas.De acuerdo a los resultados obtenidos, tanto AgNPs–CT como AgNPs–MBA, interaccionan con el DMPC a temperatura ambiente. Se observó que la magnitud de interacción AgNPs/DMPC depende de la p a la cual se encuentra el fosfolípido. Siendo una clara evidencia, de que la organización del lípido en la monocapa (o interfase y posiblemente en biomembranas) es un factor clave que regula la interacción

Metabolites from the aerial parts of the Sicilian population of Artemisia alba.

Phytochemical investigation of the CH2Cl2 extract of the aerial parts of Artemisia alba Turra afforded one new irregular sesquiterpenoid, artemiric acid, and five known metabolites: hydroxydavanone, the coumarins isofraxidin and scopoletin, (6 S*,7 S*,10 R*)–6,10-dimethyl-7,10-epoxyocta-11-enoic acid and artalbic acid. From the MeOH extract three flavonoids were identified: chrysoeriol, quercetin and isorhamnetin. The possible biogenetic pathways of artemiric and artalbic acids are discussed