Characterization of lyophilized liposomes produced with non-purified soy lecithin: a case study of casein hydrolysate microencapsulation

A commercial casein hydrolysate was microencapsulated in liposomes produced with non-purified soy lecithin, cryoprotected with two different disaccharides and lyophilized. The encapsulation efficiency of casein hydrolysate ranged from 30 to 40%. The powders were analyzed by differential scanning calorimetry (DSC), scanning electron micrography (SEM), infrared spectroscopy (FTIR) and wide angle X-ray diffraction (WAXD). DSC data revealed the presence of an exothermal transition in empty lyophilized liposomes, which was ascribed to the presence of a quasicrystalline lamellar phase (intermediary characteristics between the Lβ and Lc phases). The addition of peptides to the liposomal system caused the disappearance of this exothermic phenomenon, as they were located in the polar headgroup portion of the bilayer, causing disorder and preventing the formation of the quasicrystalline phase. Infrared data indicated the presence of the peptides in the lyophilized formulations and showed that the cryoprotectants interacted effectively with the polar heads of phospholipids in the bilayer.

Phosphatidylethanolamine and phosphatidylcholine biosynthesis by the Kennedy pathway occurs at different sites in Trypanosoma brucei

Phosphatidylethanolamine (PE) and phosphatidylcholine (PC) are among the most abundant phospholipids in biological membranes. In many eukaryotes, the CDP-ethanolamine and CDP-choline branches of the Kennedy pathway represent major and often essential routes for the production of PE and PC, with ethanolamine and choline/ethanolamine phosphotransferases (EPT and CEPT, respectively) catalysing the last reactions in the respective pathways. Although the site of PE and PC synthesis is commonly known to be the endoplasmic reticulum (ER), detailed information on the localization of the different phosphotransferases is lacking. In the unicellular parasite, Trypanosoma brucei, both branches of the Kennedy pathway are essential for cell growth in culture. We have previously reported that T. brucei EPT (TbEPT) catalyses the production of ether-type PE molecular species while T. brucei CEPT (TbCEPT) synthesizes diacyl-type PE and PC molecular species. We now show that the two enzymes localize to different sub-compartments of the ER. By expressing a series of tagged forms of the two enzymes in T. brucei parasites, in combination with sub-cellular fractionation and enzyme activity measurements, TbEPT was found exclusively in the perinuclear ER, a distinct area located close to but distinct from the nuclear membrane. In contrast, TbCEPT was detected in the bulk ER.

Effect of lipid bilayer properties on the photocycle of green proteorhodopsin

The significance of specific lipids for proton pumping by the bacterial rhodopsin proteorhodopsin (pR) was studied. To this end, it was examined whether pR preferentially binds certain lipids and whether molecular properties of the lipid environment affect the photocycle. pR's photocycle was followed by microsecond flash-photolysis in the visible spectral range. It was fastest in phosphatidylcholine liposomes (soy bean lipid), intermediate in 3-[(3-cholamidopropyl) dimethylammonio] propanesulfonate (CHAPS): 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bicelles and in Triton X-100, and slowest when pR was solubilized in CHAPS. In bicelles with different lipid compositions, the nature of the head groups, the unsaturation level and the fatty acid chain length had small effects on the photocycle. The specific affinity of pR for lipids of the expression host Escherichia coli was investigated by an optimized method of lipid isolation from purified membrane protein using two different concentrations of the detergent N-dodecyl-β-d-maltoside (DDM). We found that 11 lipids were copurified per pR molecule at 0.1% DDM, whereas essentially all lipids were stripped off from pR by 1% DDM. The relative amounts of copurified phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin did not correlate with the molar percentages normally present in E. coli cells. The results indicate a predominance of phosphatidylethanolamine species in the lipid annulus around recombinant pR that are less polar than the dominant species in the cell membrane of the expression host E. coli.

Decreased phosphatidylcholine plasmalogens - A putative novel lipid signature in patients with stable coronary artery disease and acute myocardial infarction.

OBJECTIVE Glycerophospholipids and sphingolipids are structurally heterogeneous due to differences in the O- and N-linked fatty acids and head groups. Sphingolipids also show a heterogeneity in their sphingoid base composition which up to now has been little appreciated. The aim of this study was to investigate the association of certain glycerophospholipid and sphingolipid species with stable coronary artery disease (CAD) and acute myocardial infarction (AMI). METHODS The lipid profile in plasma from patients with stable CAD (n = 18) or AMI (n = 17) was compared to healthy subjects (n = 14). Sixty five glycerophospholipid and sphingolipid species were quantified by LC-MS. The relative distribution of these lipids into lipoprotein fractions was analyzed. RESULTS In the CAD cohort, 45 glycerophospholipid and sphingolipid species were significantly lower compared to healthy controls. In the AMI group, 42 glycerophospholipid and sphingolipid species were reduced. Four PC plasmalogens (PC33:1, PC33:2, PC33:3 and PC35:3) showed the most significant difference. Out of eleven analyzed sphingoid bases, four were lower in the CAD and six in the AMI group. Sphingosine-1-phosphate (S1P) levels were reduced in the AMI group whereas an atypical C16:1 S1P was lower in both groups. Phosphatidylcholine and sphingomyelin species were exclusively present in lipoprotein particles, whereas lysophosphatidylcholines were mainly found in the lipoprotein-free fraction. The observed differences were not explained by the use of statins as confirmed in a second, independent cohort. CONCLUSIONS Reduced levels of four PC plasmalogens (PC33:1, PC33:2, PC33:3 and PC35:3) were identified as a putatively novel lipid signature for CAD and AMI.

¿Yo soy quien dice "yo"? : Consideraciones sobre la primera persona en la poesía yámbica de la Grecia arcaica

Dentro del marco de los estudios contemporáneos sobre la poesía griega antigua, dos corrientes críticas han adquirido relevancia interpretativa acerca de la naturaleza y la funcionalidad del "yo" en las composiciones líricas, elegíacas y yámbicas de la Grecia arcaica. La primera corriente entiende los textos como expresión personal del propio poeta. Desde esta perspectiva, el campo referencial que entra en juego en un poema remite siempre a la experiencia vivida por el poeta o a su reflexión íntima. Esta concepción postula una exégesis crítica tendiente a develar la poética a través de la biografía. La segunda corriente, concibe el "yo" como una construcción estereotipada o ficcional. De este modo, aquella primera persona funcionaría como un artilugio poético convencional. Nuestra presentación tiene como objetivo indagar las distintas vertientes interpretativas sobre la referencialidad del "yo" en las composiciones yámbicas de Arquíloco de Paros

El que crea que yo soy un vendedor de libros está mirando con un solo ojo : Aproximaciones al puesto de libros 'Hippie Card'

Fil: Roca Pamich, María Belén. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Qué te hace pensar que soy...?

En el presente trabajo nos interesa cuestionar el supuesto que naturaliza la diferencia sexual en los discursos sociales desde saberes/poderes bio-médicos y psicológicos, ubicando los cuerpos sexuados como posibles de ser legibles según parámetros de normalidad. A partir de ello, nos cuestionamos: ¿cómo pensar la diferencia sexual cuando las identidades esenciales se hallan estalladas en sus significaciones?. Como disparador del análisis reflexivo, elegimos algunos materiales fotográficos de intervenciones públicas que tienen a los cuerpos como protagonistas de denuncia, como locus para el ejercicio del poder en su tensión dilemática entre la regulación y el desplazamiento. Buscando instalar la propuesta de ciertos movimientos de la disidencia sexual, que tratan de resistir a la normalización de la masculinidad y la feminidad en nuestros cuerpos -a la 'policía de la identidad' dirá Butler (2012)-, y de inventar otras formas de placer y de convivencia, recuperamos la pregunta con la que nos desafía Cabral: '¿y si no hubiera más remedio que arriesgarnos a no saber cuál es el pronombre correcto, y ni siquiera saber si hay uno?; dando lugar al trabajo poético y político que disuelva una y otra vez la seguridad con la que usamos las reglas del nombrar, del desear y del coger' (Cabral, 2008, p.3)

Yo soy uno de los otros : La interpretación colectiva de textos sobre la diversidad de infancias del mundo

Fil: Paione, Alejandra Mabel. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Yo soy uno de los otros : La interpretación colectiva de textos sobre la diversidad de infancias del mundo

Fil: Paione, Alejandra Mabel. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.