Structure of Gel Phase DMPC Determined by X-Ray Diffraction

Abstract

The structure of fully hydrated gel phase dimyristoylphosphatidylcholine lipid bilayers was obtained at 10 degrees C. Oriented lipid multilayers were used to obtain high signal-to-noise intensity data. The chain tilt angle and an estimate of the methylene electron density were obtained from wide angle reflections. The chain tilt angle is measured to be 32.3 +/- 0.6 degrees near full hydration, and it does not change as the sample is mildly dehydrated from a repeat spacing of D = 59.9 A to D = 56.5 A. Low angle diffraction peaks were obtained up to the tenth order for 17 samples with variable D and prepared by three different methods with different geometries. In addition to the usual Fourier reconstructions of the electron density profiles, model electron density profiles were fit to all the low angle data simultaneously while constraining the model to include the wide-angle data and the measured lipid volume. Results are obtained for area/lipid (A = 47.2 +/- 0.5 A(2)), the compressibility modulus (K(A) = 500 +/- 100 dyn/cm), various thicknesses, such as the hydrocarbon thickness (2D(C) = 30.3 +/- 0.2 A), and the head-to-head spacing (D(HH) = 40.1 +/- 0.1 A).

Adsorbed liposome deformation studied with quartz crystal microbalance

“…27,35 For instance, Tristam-Nagle et al 27 give κ ∼ 10 × 10 −19 J for the gel phase of DMPC, which is similar to the value obtained for DPPC in the same phase, as shown in Figure 4(a). 26 Third, we show in Figure 4(b) that the size of DMPC liposomes in solution (not adsorbed to a surface) increases with temperature.…”

Mesoscopic Simulations of Biological Membranes

“…While single-tail lipids are not tilted in the gel phase, for the double-tail lipid we observe that the lipid chains are tilted with respect to the bilayer normal. We find a tilt angle of 25 • , which is slightly lower than the value of ≈ 32 • measured experimentally for DMPC lipid bilayers [68]. A typical configuration at this temperature can be see in the snapshot in Fig.…”

Crystalline Domain Structure and Cholesterol Crystal Nucleation in Single Hydrated DPPC:Cholesterol:POPC Bilayers

“…23 The l o and S o phases include crystalline domains detectable by X-ray diffraction. 16,[24][25][26][27][28][29] Their coherence lengths are typically nanometers in the l o phase and tens of nanometers in the S o phase.…”