TABLE 1.

Fluorescence properties of reconstituted KcsA

Phospholipid	Emission max (nm)	n number	Quenching by brominated lipid (F/F)o
DOPC	332.6 ± 0.2	1.69	0.61 ± 0.01
DOPA	331.8 ± 0.2	2.49 ± 0.25	0.48 ± 0.01
DOPE	331.9 ± 0.1	1.77 ± 0.27	0.62 ± 0.01
DOPG	332.1 ± 0.2	1.53 ± 0.12	0.58 ± 0.01
DOPS	331.2 ± 0.3	1.77 ± 0.12	0.49 ± 0.01
TOCL	332.5 ± 0.4	0.90 ± 0.15	0.63 ± 0.04

Wavelengths of maximum emission were determined by fitting the fluorescence emission spectra to a skewed Gaussian peak as described under Experimental Procedures. n is the number of lattice sites close enough to a Trp residue to cause quenching when occupied by a brominated lipid and was obtained by fitting quenching data to Eq. 1. The value of n for DOPC is the average value reported previously for quenching in brominated phosphatidylcholines (Williamson et al., 2002). Levels of quenching in brominated lipid were determined as F/F_o where F_o is the fluorescence intensity in DOPC and F is the fluorescence intensity in the corresponding brominated phospholipid. For DOPE the value of F/F_o corresponds to that recorded in a 9:1 mixture of BrPE:DOPC. For all measurements the buffer was 20 mM HEPES and 1 mM EGTA at pH 7.2.