FIGURE 1.

Far-UV CD spectra of the nonchannel (- - -), intermediate I (- · -), intermediate II (· · ·), and channel (—) forms of gramicidin in vesicles of POPC. The various forms of gramicidin were generated as described in the text. The channel conformation was prepared by sonication followed by heat incubation at 65°C for 12 h and the nonchannel conformation was generated by the ethanol injection method. Intermediate I was generated by ethanol injection followed by 65°C incubation for 12 h. Intermediate II was formed by ethanol injection followed by sonication and 65°C incubation for 12 h. The ratio of gramicidin to POPC was 1:50 (mol/mol). See Materials and Methods for other details.