Electronic Conduction in Liquid Crystalline Membranes Role of Unsaturated Lipids

Electronic Conduction in Liquid Crystalline Membranes. Role of Unsaturated Lipids 

One class of organic conductors are polyenes in which conductivity is due to intramolecular overlapping n orbitals. The different modes of soliton conduction have been reviewed by MacDiarmid and Heeger. The practical use of polyenes is limited by thermally activated chain rotation, which interrupts the conjugation. Stacked, planar delocalized 

We propose the unsaturated lipids of biological membranes to provide the cells with an electronic conduction band. A striking feature of the unsaturated lipids in biomembranes is the very constant location of ethylenic cw-double bond in monounsaturated acyl chains between carbon atoms 9 and 10. A noteworthy exception is nervonic add (cw-15-24 1), which is abundant in central nervous system membranes. A microviscosity barrier has been observed in bilayers of dioleoylphosphatidylchohne at the depth of the oleic acid double bonds.Phospholipids belong to lyotropic liquid crystals and possess remarkable short- and long-range order. In a cell membrane lattice the local concentration of ester carbonyls and acyl chain ethylenic double bonds as well as the local concentration of cholesterol C=C bonds is very high. 

Both (i) and (ii) are commensurate with good conduction. Their validity is not limited to four ethylenic bonds but can be applied to a helically arranged system consisting of several double bonds. An example of the latter can be found in dolichol.  

FIGURE 1. Schematic illustration of the HOMO and LUMO of a supermolecule consisting of four strongly interacting ethylenic double bonds. See text for details. 

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