Proton field cycling NMR relaxometry of lipid bilayer membranes containing cholesterol. FFC membrane elastometry.

ESTEBAN ANOARDO

Conferencia; 8th Conference on Fast Field Cycling NMR Relaxometry; 2013

It was previously demonstrated that fast field cycling (FFC) 1 H NMR spin-lattice relaxation ratedispersions of liposomes can be explained through a physical model that accounts for themolecular dynamics of the lipids [1,2]. The model was successfully compared withexperimental measurements of liposomes prepared with different lipids (DMPC and DOPC),sizes (100-200nm) and temperatures (within the fluid liquid crystalline phase), using values forthe different physical constants and parameters available in the literature. Then, the FFC NMR method was shown to be a useful tool for the study of the molecular dynamics of lipids and theviscoelastic properties of biological membranes. In the presence of cholesterol, two differentpictures can be considered:  a- The cholesterol modulates the viscoelastic properties of the membrane, and consequently, theobserved value of the mesoscopic involved physical parameters [3]. b- The cholesterol molecule exerts a strong influence in the lipids around it, thus separating thelipid population in two groups (cholesterol-ordered and disordered) [4].  The two pictures can be confronted with the model previously tested in cholesterol-freemembranes, validating its extension to the present case.  Based on these studies, a method for the measurement of the bending elastic modulus ofliposome membranes has been considered. An experiment was performed in order to test thefeasibility of these measurements at limiting technological conditions (low cost/low size & fastmeasuring instrumentation). [1]- Meledandri, C.J.; Perlo, J.; Farrher, E.; Brougham, D.F.; Anoardo, E. J. Phys. Chem. B,2009, 113, 15532. [2]- Perlo J., Meledandri C. J., Anoardo E., Brougham D. F. J. Phys. Chem. B, 2011, 115, 3444.[3]- Filippov A., Orädd G., Lindblom G. Biophys. J. 2003, 84, 3079.[4]- Dai J., Alwarawrah M., Huang J. J. Phys. Chem. B, 2010, 114, 840.