[Structure and permeability of the contact zone of 2 artificial lipid-lipoprotein membranes]

Contact interaction of two flat artificial lipid-proteolipid membranes (LPLM) obtained from lipid-proteolipid mixture of cattle brain white matter was studied. Investigation of the optical structure of the contact region revealed existence of fused proteolipid (PL) nodes and bilayer lipid areas. The lipid bilayers are fixed at stationary distance--30-40 nm, irrespective of ionic composition and ionic strength of the aqueous medium. Apparently, the maximal thickness of proteolipid regions at the two sides of the lipid framework of single LPLM reaches 15-20 nm, and LPLM after putting into contact fused in the region of PL nodes. It prevents the lipid areas from further drawing together. Conductance of the contact zone of two LPLM in NaCl solutions (10 and 100 mM) corresponds to that of single LPLM, but in KCl solutions it decreases 3.5 times, remaining in all the cases 1-2 orders above the conductance of single bilayer lipid membrane (BLM) or the contact zone of two BLM. Conductivity of single as well as of two contacting LPLM is higher for K+, than for Na+. The data obtained suggest that PL areas of the contact zone of two LPLM, likewise a single LPLM, are adjacent to the aqueous medium forming together with the bound lipids the zones of high conductivity.