Thermodynamic and topologic characterization of mammal and insect natural membranes at the air-water interphase

COLMANO, GUILLERMO NICOLÁS; FELSZTYNA, IVÁN; SÁNCHEZ-BORZONE, MARIELA EUGENIA; GARCÍA, DANIEL ASMED; TURINA, ANAHÍ DEL VALLE

Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

Sociedades de Biociencias

The aim of the present work was to characterize natural membranes by studying their ability to form stable monolayers at the airwater interface (Langmuir flms) and the topology of the formed flms.The natural membranes were synaptosomal membranes obtainedfrom 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 byquantifcation 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 naturalmembrane at the interface and no isotherm shape differences wereobserved.Langmuir flms isotherms showed clear differences between mammalian and insect membranes. The SM Langmuir flm exhibited acollapse pressure of pc = 50 ± 0.2 mN/m at a minimal area of Amin =100.4 Å2 and a typical phase transition at 36 mN/m, usually associated with protein reorganization at the surface. On the other hand,GM showed a pcbetween 45-47 ± 0.2 mN/m at Amin = 105 Å2 but thephase transition was not present.Langmuir flms were also observed with an inverted epifluorescence microscope (EFM) to evaluate the topology of the monolayersas well as for checking the absence of vesicles in the subphase. SMand GM were doped with 1mol% of Dil-C18 and directly observedfrom the interface or transferred to a solid support.In Langmuir flms, vesicles were identifed as big bright dots inEFM images. The wet bridge spreading method did not prevent theapparition of vesicles, though it reduced the number of vesicles considerably, resulting the most appropriate.