A useful technique for understanding the influence of lipid environment on membrane proteins is planar bilayer recording, in which proteins are ‘extracted’ from biological membranes and incorporated into a highly simplified lipid film painted across an opening in the recording chamber. By using transfected cells, from which BK proteins are extracted, channel identity can be controlled. Single channel activity can then be recorded as a function of desired bilayer composition and presence of alcohol. The bilayer preparation allows some very interesting questions to be posed: e.g. ‘how much organized membrane and cell are necessary to observe acute molecular tolerance?’ The answer is ‘remarkably little’ – i.e. acute tolerance is observable in isolated BK channels transposed into reconstituted bilayers [47]. But bilayer composition has a very large effect. The acute ethanol tolerance observed in stable (20:1) phosphatidylcholine–dioleoylphosphatidylethanola-mine (PC–DOPE) bilayers is not observed in sphingomyelin–DOPE bilayers [47]. One suggestion to explain this effect is that acute molecular tolerance to ethanol involves interaction with multiple sites perhaps with opposing (i.e. potentiating versus inhibiting) effects within the BK channel, and changes in lipid environment
