Thermodinamic and topologic characterization of mammal and insect natural membranes in the air-water interphase

FELSZTYNA, IVAN; TURINA, ANAHI DEL VALLE; COLMANO, G. NICOLAS; GARCIA, DANIEL ; SANCHEZ-BORZONE, MARIELA

Buenos Aires

Congreso; Reunion conjunta de sociedades de biociencias; 2017

The aim of the present work was to characterize natural membranes by studying their ability to form stable monolayers at the air water interface (Langmuir films) and the topology of the formed films.The natural membranes were synaptosomal membranes obtained from bovine brain cerebral cortex (SM) and ganglion membranes (GM) prepared from the head-thorax portion of Aedes aegypti larvae (IV stage) or Triatoma infestans nymphs (V stage).The general composition of the membranes was determined by quantification of protein, phosphoplipids and cholesterol total content.Mammalian and insect membranes were able to form compressible monomolecular layers at the air water interface. Different methods were tried to spread the aqueous suspension of the natural membrane at the interface and no isotherm shape differences were observed.Langmuir films isotherms showed clear differences between mammalian and insect membranes. The SM Langmuir film exhibited a collapse pressure of pi = 48 ± 1.2 mN/m and a typical phase transition at 36 mN/m, usually associated with protein reorganization at the surface. On the other hand, the more expanded GM films showed a pi= 30 ± 0.6 mN/m with a less cooperative transition at 15mN/m. Langmuir films were also observed with an inverted epifluorescence microscope (EFM) to evaluate the topology of the monolayers as well as for checking the absence of vesicles in the subphase. SM and GM were doped with 1mol% of Dil-C18 and directly observed from the interface. In Langmuir films, vesicles were identified as big bright dots in EFM images. The wet bridge spreading method did not prevent the apparition of vesicles, though it reduced the number of vesicles considerably, resulting the most appropriate.