Details

Autor(en) / Beteiligte

• Perutková, Šárka
• Daniel, Matej
• Rappolt, Michael
• Pabst, Georg
• Dolinar, Gregor
• Kralj-Igli, Veronika
• Igli, Aleš

Titel

Elastic deformations in hexagonal phases studied by small-angle X-ray diffraction and simulationsThis article was submitted as part of a special collection on scattering methods applied to soft matter, marking the 65th birthday of Professor Otto Glatter

Erscheinungsjahr

2011-02

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• In this study we present experimental and theoretical results which concern the deviations from circularity of the pivotal plane in the inverse hexagonal phases (H II ) of phospholipidself-assemblies. Due to packing constraints, the cross-section of the polar/apolar interface deviates from a circle, which we studied in minute detail by analysing small-angle X-ray diffraction data of dioleoyl-phosphatidylethanolamine (DOPE) and stearoyl-oleoyl-phosphatidylethanolamine (SOPE), respectively. On this structural basis, Monte Carlo (MC) simulated annealing variations of the free energy were carried out, both on the formation of the H II -phase and on the particular shape of the cross-section in the H II -phase. The equilibrium of the H II -phase pivotal plane contour and the corresponding values of the mean intrinsic curvature, H m , and the hydrocarbon chain stiffness, τ , were determined from MC calculations. The results of these calculations were tested by solving the corresponding system of non-linear differential equations derived using variational calculus. Here our main aim is to predict the range of possible values of H m and τ . Comparing the measured structural data with predictions from MC calculations including lipid anisotropy, and accounting for the elastic deformations of the pivotal plane allowed us to determine a relationship between the bending deformation and stretching of hydrocarbon chains. Theoretical insights taking into account the non-circular geometry of the H II -phase cross-section and anisotropy of phospholipids were validated by small-angle X-ray diffraction.