Calculating order parameter profiles utilizing magnetically aligned phospholipid bilayers for ²H solid-state NMR studies

Solid-state deuterium NMR spectroscopy was used to study the structural and dynamic properties of stearic acid-d₃₅ in magnetically aligned phospholipid bilayers as a function of temperature. Magnetically aligned phospholipid bilayers or bicelles are model systems, which mimic biological membranes for magnetic resonance studies. Paramagnetic lanthanide ions (Yb ³⁺) were added to align the bicelles such that the bilayer normal is colinear with the direction of the static magnetic field. The corresponding order parameters of the stearic acid-d₃₅ probe were calculated and compared with values obtained from unoriented samples in the literature. The addition of cholesterol to the bicelle system decreases the fluidity of the phospholipid bilayers and increases the ordering of the acyl chains of stearic acid-d₃₅. This study demonstrates the feasibility of utilizing magnetically aligned bicelles for calculating ²H order parameter profiles for non-biological systems such as polymer-grafted membranes and Schiff's base complexes.