10.1184/R1/6508199.v1 Stephanie Tristram-Nagle Stephanie Tristram-Nagle Yufeng Liu Yufeng Liu Justin Legleiter Justin Legleiter John F. Nagle John F. Nagle Structure of Gel Phase DMPC Determined by X-Ray Diffraction Carnegie Mellon University 2002 Physics 2002-12-01 00:00:00 Journal contribution https://kilthub.cmu.edu/articles/journal_contribution/Structure_of_Gel_Phase_DMPC_Determined_by_X-Ray_Diffraction/6508199 <p>The structure of fully hydrated gel phase dimyristoylphosphatidylcholine lipid bilayers was obtained at 10°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<sup>o</sup> near full hydration, and it does not change as the sample is mildly dehydrated from a repeat spacing of <em>D</em>=59.9Å to <em>D</em>=56.5Å. Low angle diffraction peaks were obtained up to the tenth order for 17 samples with variable <em>D</em> 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 (<em>A</em>=47.2±0.5Å<sup>2</sup>), the compressibility modulus (<em>K</em><sub>A</sub>=500±100 dyn/cm), various thicknesses, such as the hydrocarbon thickness (2<em>D</em><sub>C</sub>=30.3±0.2Å), and the head-to-head spacing (<em>D</em><sub>HH</sub>=40.1±0.1Å).</p>