2H NMR spectra of DMPC-d54 MLV samples as a function of concentration and pH: (A) DMPC-d54 bilayer with 0, 5, and 10 mol % sorbic acid at pH 3.0, (B) pH 4.4, (C) pH 6.0, (D) pH 7.4, (E) decanoic acid at pH 4.4, and (F) decanoic acid at pH 7.4, obtained using a quadrupolar echo pulse sequence under static condition at 35 °C.