ABSTRACT
Stacked membranes are model systems for elucidating the statistical mechanical properties of real cellular membranes. In the first part of the chapter, we describe phase behaviour in the chain-ordered gel phase of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), commonly present in biological membranes. X-ray scattering in freely suspended DMPC films reveals that the L β ′ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429194078/f6648c05-54f1-4ef3-aa21-f4b9bfd91090/content/C002_equ_0001.tif"/> gel phase of biological membranes, identified in powder preparations, is composed of distinct 2D lamellar phases, L β F https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429194078/f6648c05-54f1-4ef3-aa21-f4b9bfd91090/content/C002_equ_0002.tif"/> , L β L https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429194078/f6648c05-54f1-4ef3-aa21-f4b9bfd91090/content/C002_equ_0003.tif"/> , and L β I https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429194078/f6648c05-54f1-4ef3-aa21-f4b9bfd91090/content/C002_equ_0004.tif"/> , distinguished by the direction of chain tilt within the membrane. In the second part, we describe intermembrane interactions in the dilute lamellar L α https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429194078/f6648c05-54f1-4ef3-aa21-f4b9bfd91090/content/C002_equ_0005.tif"/> phase of fluid membranes in a quaternary surfactant/cosurfactant system. X-ray scattering experiments show that the phase, which displays characteristics of Landau–Peierls systems, is stabilized by entropically mediated Helfrich undulation forces. The chapter introduces X-ray scattering and reflectometry techniques for ascertaining the intra- and intermolecular lipid arrangement and X-ray scattering for probing interlayer interactions by analysis of thermal diffuse scattering.
