Table 1. Structural data deduced from the off-specular determination of electron density profiles.

Lipid no.	Phase	VL, nm3	AL, nm2	DHH, nm
17	Gel	1.267	0.49	4.7
	Fluid		0.55	4.6
18	Gel	1.315	0.50	4.95
	Fluid		0.54	4.85

Uncertainties: lipid volume V_L, 0.015 nm³; lipid area A_L, 0.03 nm²; head-to-head distance D_HH, 0.2 nm.