This work summarizes the results obtained from the modification of perfluorinated sulfocationic MF-4SC membranes by in situ polymerization of aniline. The transport properties of polyaniline/MF-4SC composite membranes after different times of polymerization have been analyzed. It is observed that after 3 h of aniline polymerization, composite membranes exhibit higher protonic conductivity compared to the pristine sample. The performance of fuel cells containing membrane electrode assemblies (MEAs) from MF-4SC and polyaniline/MF-4SC has also been studied. The kinetic parameters governing the voltage dependence on current density have been estimated and the results have been fitted to a previously established one-dimensional isothermal model by Springer et al. [ J. Electrochem. Soc. 138 , 2334 (1991)] . Good agreement between experimental data and model has been found for low density currents. Some insights about the membrane proton conductivity mechanism are given.

During the last decade, considerable evidence is accumulating that supports the view that the classic progesterone receptor (xPR-1) is mediating Xenopus laevis oocyte maturation through a non-genomic mechanism. Overexpression and depletion of oocyte xPR-1 have been shown to accelerate and to block progesterone-induced oocyte maturation, respectively. In addition, rapid inhibition of plasma membrane adenylyl cyclase (AC) by the steroid hormone, supports the idea that xPR-1 should be localized at the oocyte plasma membrane. To test this hypothesis, we transiently transfected xPR-1 cDNA into Cos-7 cells and analyzed its subcellular distribution. Through Western blot and immunofluorescence analysis, we were able to detect xPR-1 associated to the plasma membrane of transfected Cos-7 cells. Additionally, using Progesterone-BSA-FITC, we identified specific progesterone-binding sites at the cell surface of xPR-1 expressing cells. Finally, we found that the receptor ligand-binding domain displayed membrane localization, in contrast to the N-terminal domain, which expressed in similar levels, remained cytosolic. Overall, these results indicate that a fraction of xPR-1 expressed in Cos-7 cells, associates to the plasma membrane through its LBD.

This work summarizes results on the modification of perfluorinated sulfocationic membranes MF-4SC by polymerization in situ of aniline. The investigation of the transport properties of polyaniline/MF-4SC composites membranes after different times of polymerization has been analyzed. After 3 hours of aniline polymerizacion, both pristine and composite membranes exhibit higher protonic conductivity. The performance of fuel cells containing MEAs from MF-4SC and polyaniline/MF-4SC was studied and the kinetic parameters governing the voltage dependence on current density estimated.

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