Synkinesis of Asymmetric Vesicle Membranes In-Out

A topological detail unique to vesicle membranes lies in the possibility of arranging several thousands of head groups A on the outer surface of the membrane and a similar number of head groups B on the inner surface. This is particularly interesting if B is an electron donor and A an acceptor, or vice versa. A membrane-dissolved dye may then, in its excited state, donate electrons to A and be re-reduced by B. A and B radicals on both sides of the membranes would then be formed and could possibly induce further chemical redox reactions, e.g. the splitting of water (see sections 3.7 and 4.4). 

In nature, asymmetry is achieved through membrane dissolved proteins. In lipid membrane systems without proteins, only monolayers made of bola-amphiphiles allow a totally asymmetric arrangement of head groups. The simplest asymmetry to be achieved is dependent on the one-sided precipitation of bolaamphiphiles. a,to-Dicarboxylic acids, for example, are often soluble at pH 8 and spontaneously form vesicles upon acidification to pH 5. At a lower pH, all carboxyl groups become protonated and one usually observes ill-defined precipitates . 

A mixture of negatively charged phosphatidic acid and phosphatidylcholine was cosonicated. This system was used to quantify the metachromatic effects of 

Cestaro, E. Pistolesi, N. Hershhowitz, S. Gatt, Biochim. Biophys. Acta, 1982, 685, 13 

Reaverage time, or so-called flip-flop time , is important in respect to membrane asymmetry. It measures the time taken for an amphiphile to exchange 

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