Biomimetic Monolayer Films of MonogalactosyldiacylglycerolIncorporating Plastoquinone.

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]