Table 2. Thermodynamics and kinetics associated with cholesterol/cholestenone flip-flop and desorption.

Model system		ΔGdesorb a (kJ/mol)	ΔGbarrier b (kJ/mol)	ΔGcenter c (kJ/mol)	td (ns)	kd (S−1)	kf (S−1)	kflip (S−1)
chol	IFE (POPC/PSM/chol/cnone 2∶1∶1∶0)	76.0±2.7	26.0±1.2	25.0±1.0	1–80	1.3×107 to 109	7.8×102 to 6.0×104	4.0×102 to 3×104
	IIFE (POPC/PSM/chol/cnone 2∶1∶0.75∶0.25)	70.6±1.6	23.5±0.9	22.5±0.6	1–80	1.3×107 to 109	2.2×103 to 1.7×105	1.1×103 to 0.9×105
	IVFE (127 POPCs and 1 chol)	62±2.4	19.0±1.3	18.0±0.9	1–80	1.3×107 to 109	1.2×104 to 9.1×105	0.6×104 to 4.6×105
cnone	IIFE (POPC/PSM/chol/cnone 2∶1∶0.75∶0.25)	65.4±1.5	8.0±0.6	6.4±0.3	1–40	2.5×107 to 109	2.1×106 to 8.2×107	1.1×106 to 4.1×107
	IIIFE (POPC/PSM/chol/cnone 2∶1∶0∶1)	61.3±2.3	5.8±0.9	4.1±0.7	1–40	2.5×107 to 109	5.0×106 to 2.0×108	2.5×106 to 108
	VFE (127 POPCs and 1 cnone)	57.8±1.7	4.9±0.9	3.5±0.6	1–40	2.5×107 to 109	6.3×106 to 2.5×108	3.2×106 to 1.3×108

^aΔG_desorb is the free energy barrier for desorption from membrane to water phase.

^bΔG_barrier is the free energy barrier for flip-flop.

^cΔG_center is the difference in free energy between the bilayer center (Z_center) and the equilibrium position (Z_eq).

The parameters k_d, k_f, k_flip, and t_d are defined and discussed in Materials and Methods.