Asymmetric planar bilayer membranes

Tab. 4.32 Molecular parameters describing the (glyco)lipids constituting the bilayer leaflet at the side of PMB addition of various asymmetric planar bilayers (the second leaflet was always made from the phospholipid mixture) and the average diameters of the induced membrane lesions. (Reprinted from Tab. 1 of ref. 117 with permission from Bertelsmann-Springer.)...

A new family of crown-ether-based bolaamphiphiles, 21, that aggregate into a previously unknown type of bolaamphisome was prepared by Gokel and coworkers [50]. Evidence was presented on vesicle formation from the aqueous suspension of such bolaform amphiphiles. Several reports describing the synthesis of various macrocyclic models related to archael compounds have also appeared in the literature [51]. Fyles et al. prepared a novel series of asymmetric bis-macrocyclic bolaphiles, 22, and evaluated their transport activities in vesicles and planar bilayer membranes [52]. 

Artificial asymmetric membranes composed of outer membranes of various species of Gram-negative bacteria and an inner leaflet of various phospholipids have been prepared using the Montal-Mueller technique [65]. Such planar bilayers have been used, for example, to study the molecular mechanism of polymyxin B-mem-brane interactions. A direct correlation between surface charge density and self-promoted transport has been found [66]. 

Net reaction between hydrophilic oxidants and reductants separated by bilayer membranes has been convincingly demonstrated in numerous asymmetrically organized vesicle and planar bilayer systems [2a-c]. Particularly compelling examples are those in which electrogenic electron transport is accompanied by net translocation of lipophilic cations or anions, as is required to maintain electroneutrality. For example, MV + occluded within the inner aqueous phase of DHP vesicles can be completely reduced to the MV+ radical cation by 8204 ion in the bulk phase, but only if an equal or greater amount of viologen is initially present in the external environment [40]. Neither MV-+ nor 8204 is membrane permeable. The reaction is biphasic, with rapid bimolecular reduction of external being followed by... 

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