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Highlights • Biomimetic membranes are prepared using the natural myriad of each lipid structures that constitute the bacterial membrane. • The biomimetic membranes are very elastic due to the presence of several unsaturations in the lipids structures. • The model membranes present the same physical state and minor rigidity differences regardless the PE:PG or PE:CL ratio. • The similar rigidity suggests that the changes in the lipid composition may influence the membrane proteins function. Abstract Novel antimicrobial agents are focused to interact with the bacterial membrane whose lipid composition (number and position of unsaturations and lipid headgroup) is adapted according to environmental signals. The anticipation of the adapted membrane properties is of high relevance to increase the targetability of such drugs. Herein, natural lipids extracted from Escherichia coli -phosphatidylethanolamine (PE), phosphatidylglycerol (PG) and cardiolipin (CL)- are used to form biomimetic membranes constituted by several PE:lipid ratios using the Langmuir and Langmuir-Blodgett techniques. The use of these techniques and the natural myriad of each lipid structures that constitute the biological E.coli membrane establishes a simple and reproducible model to evaluate the lipid-lipid interactions. PE and PG present similar shape and size, thus establish ideal and fluid -liquid expanded (LE) state - mixtures, whereas the differences between PE and CL motivate the formation of non-ideal and fluid (LE state) mixtures. The same physical state and the minor differences in elasticity (differences in the inverse of the compressibility modulus < 15 mN·m−1) between both systems regardless the PE content in the (PE:lipid) mixture suggest that the changes in the lipid composition influence the membrane proteins function rather than affecting the rigidity of the bacterial membrane. [ABSTRACT FROM AUTHOR]

Abstract.: The relevance of biomimetic membranes using galactolipids has not been expressed in any extensive experimental study of these lipids. Thus, on the one hand, we present an in-depth article about the presence and role of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) in thylakoid membranes, their physical states and their applications. On the other hand, we use the Langmuir and Langmuir-Blodgett (LB) techniques to prepare biomimetic monolayers of saturated galactolipids MGDG, DGDG and MGDG:DGDG 2:1 mixture (MD)--biological ratio--. These monolayers are studied using surface pressure-area isotherms and their data are processed to enlighten their physical states and mixing behaviour. These monolayers, once transferred to a solid substrate at several surface pressures are topographically studied on mica using atomic force microscopy (AFM) and using cyclic voltammetry for studying the electrochemical behaviour of the monolayers once transferred to indium-tin oxide (ITO), which has good optical and electrical properties. Moreover, MD presents other differences in comparison with its pure components that are explained by the presence of different kinds of galactosyl headgroups that restrict the optimal orientation of the MGDG headgroups. Graphical abstract: [ABSTRACT FROM AUTHOR]

Photosyntheticorganisms use light to convert the inorganic matterin organic one. Photosynthetic process consists on several steps,and one of them involves plastoquinone (PQ) that acts as electronand proton shuttle between photosystem II and cytochrome. We preparedmembranes that mimic the characteristics and composition of naturalphotosynthetic membranes and we characterized them using several techniquesin order to obtain both the PQ molecules disposition in the membraneand their electrochemical behavior. The selected lipid was monogalactosyldiacylglycerol(MGDG) that represents the 50% of the lipid content of the thylakoidmembrane. Both MGDG and PQ, and the MGDG:PQ mixtures have been studiedusing surface pressure–area isotherms and the presence of PQalters the physical state and compactness of the MGDG matrix. Langmuir–Blodgett(LB) films have been obtained by transferring a monolayer that mimicshalf of the bilayer of a biological membrane. The AFM topographicalcharacterization of the monolayers on mica indicates the presenceof differentiated domains, corresponding to different physical stateslinked to the influence of the PQ content. Moreover, the electrochemicalbehavior of the monolayers has been studied when transferred on ITO,observing one main electrochemical process that is due to the divingposition of PQ molecules in the lipid matrix. [ABSTRACT FROM AUTHOR]