Molecular dynamic heterogeneity of confined lipid films by 1H magnetization-exchange nuclear magnetic resonance.
The molecular dynamic heterogeneity of monolayer to submonolayer thin lecithin films confined to submicron cylindrical pores were investigated by 1H magnetization exchange nuclear magnetic resonance. In this experiment a z-magnetization gradient was generated by a double-quantum dipolar filter. The magnetization-exchange decay and buildup curves were interpreted with the help of a theoretical model based on the approximation of a one-dimensional spin-diffusion process in a three-domain morphology. The dynamic heterogeneity of the fatty acid chains and the effects of the surface area per molecule, the diameter of the pores, and the temperature were characterized with the help of local spin-diffusion coefficients. The effect of various parameters on the molecular dynamics of the mobile region of the fatty acid chains was quantified by introducing an ad hoc Gaussian distribution function of the 1H residual dipolar couplings. For the lipid films investigated in this study, the surface induced order and the geometrical confinement affect the chain dynamics of the entire molecule. Therefore, each part of the chain independently reflects the effect of surface coverage, pore size, and temperature.
Buda
A
A
Institut für Technische Chemie und Makromolekulare Chemie, RWTH Aachen, D-52056, Aachen, Germany. abuda@mc.rwth-aachen.de
Demco
D E
DE
Jagadeesh
B
B
Blümich
B
B
D000537:Aluminum Oxide; D005227:Fatty Acids / Q000737:chemistry; D008280:Magnetics; D008956:Models, Chemical; D019906:Nuclear Magnetic Resonance, Biomolecular; D010713:Phosphatidylcholines / Q000737:chemistry*; D016062:Porosity; D013113:Spin Labels; D013696:Temperature
D005227:Fatty Acids; D010713:Phosphatidylcholines; D013113:Spin Labels; D000537:Aluminum Oxide