Quantized Nature, and the Influence o

that the changes in lateral compressibility lead to a facilitation of pore formation since the increased compressibility lowers the work necessary to create a membrane defect. In the melting transition, one also finds domain formation. Papahad-jopoulos et al. (7) suggested in their seminal article that permeation events take place at domain boundaries. This view has also been adopted by Cruzeiro-Hansson and Mour-itsen (10) and Corvera et al. (11). At domain boundaries, fluc-tuations in lipid state are maximal, and this suggests that domain interfaces are especially leaky. However, this view is not identical to that of Nagle and Scott (8) since the overall length of domain interfaces is not identical to large fluctua-reported for ion channel proteins. Although there is, to our knowledge, no convincing explanation of why such currents should be quantized, there are several publications document-ing such channellike behavior. The first article on this is from Yafuso et al. (13) on oxidized cholesterol films, which appeared two years before the famous article by Neher and Sakmann (14) on quantized currents through the acetylcho-line receptor (quantized currents through protein-containing BLMs were actually already shown significantly earlier by (15)). Antonov et al. (3) were the first to show that these lipid membrane conduction events are strongly enhanced in the phase transition regime. Using pure synthetic lipids, they could switch permeation on and off merely by shifting the temperature by a few degrees. This basically rules out the possibility that one is observing proteins or peptide impu-rities. Kaufmann and Silman (16,17) andKaufmann et al. (18) showed that the occurrence of such lipid ion channels depends not only on temperature but also on other intensive variable