TABLE 3.

Average membrane penetration depths of gramicidin tryptophans in the channel and nonchannel forms by the parallax method

Gramicidin conformation	Depth from the center of the bilayer zcF (Å)
Nonchannel	7.3
Channel	11.0

Depths were calculated from fluorescence quenchings obtained with samples containing 15 mol % of 5-PC and 12-PC and using Eq. 8. Samples were excited at 280 nm, and emission was monitored at 331 nm. The ratio of gramicidin to total lipid was 1:50 (mol/mol). See Materials and Methods for other details.