TABLE 6.

Fractions, f, of motionally restricted spin-labeled lipid in DMPC membranes containing gramicidin A

	TFE		CHCl3:MeOH
Spin label*	f		f
14-PCSL	0.39	1.0	0.63	1.0
14-PASL	0.44	1.2	0.65	1.1
14-PESL	0.34	0.8	0.52	0.6
14-PGSL	0.35	0.8	0.53	0.7
14-PSSL	0.42	1.1	0.65	1.1
14-SASL (pH 4.5)	0.30	0.7	0.48	0.5
14-SASL (pH 9.0)	0.48	1.4	0.69	1.3

Shown are fractions, f, of motionally restricted spin-labeled lipid in DMPC membranes containing gramicidin A at 1:10 molar ratio. K_r/K_r^PC is the relative association constant, normalized to 14-PCSL.

^*Samples are prepared from TFE or from CHCl₃:MeOH (2:1 v/v) and are buffered at pH 7.8, except for 14-SASL. Typical uncertainty in f from fitting the two-component spectra is ±0.01–0.02.