Properties of membranes with different sterols and hopanoids?

A. MANGIAROTTI Y N. WILKE

Tucumán

Congreso; Reunión conjunta: III LAFeBS, IX Iberoamerican Congress of Biophysics, XLV SAB.; 2016

It has been proved that liquid-ordered phases may be present in themembrane of organisms of different kingdoms, however there is alack of systematic studies in which the differences and similitudes betweenthe different sterols and hopanoids are evaluated together. Therefore,we are interested in investigating how the presence of sterolsand hopanoids regulate the properties of the membranes using differentmodel systems for lipid bilayers and monolayers.In this work, as a first approach, we used fluorescence microscopy inorder to construct phase diagrams for canonical raft mixtures containingDOPC, DPPC and different sterols (cholesterol, ergosterol or stigmasterol)and diplopterol, an hopanoid. We observed that in Langmuirmonolayers at the air-water interface ergosterol presents phase coexistencein a wider range of surface pressures than the rest of the testedcompounds. For mixtures containing the phytosterol stigmasterol, thephase coexistence region is very thin, but a second two phase regionexists near a surface pressure of 20mNm􀀀1 at 10% of the sterol. This behavior was also observed for cholesterol at 10%. Interestingly, fordiplopterol, a two phase region was observed between 0-6mNm􀀀1 andthe domains presented an elongated worm-like shape, suggesting thatwith this particular mixture of phospholipids, the hopanoid form a condensedphase instead of a Lo phase. In planar free-standing bilayers,10% of the different compounds in the same lipid system led to differentphase behaviors.