Table I. Comparison of R₁₈-Labeled Plasma Membrane Fusion with Various Target Membranes^a.

Target membrane	Addition	Lag time (sec)	IRF (%) = ΔF/time
Disks	10 μM Ca2+	<20	2.9 ± 0.04
Rim-specific vesicles	10 μM Ca2+	20–50	0.26 ± 0.02
Peripherin/rds LUVs	10 μM Ca2+	120	0.30 ± 0.03

^aFusion of R₁₈–PMs with disk membranes,¹² isolated rim-specific vesicles, and peripherin/rds recombinant LUVs²³ at 37°. The initial rate of fusion is given as the percent change in fluorescence intensity per unit time (minutes with disk membranes and seconds with rim-specific vesicles and peripherin/rds LUVs).