An additional component is observed in the center of the low-temperature C30d spectra in bulk and in the membrane. For the bulk sample, this component appears as a very narrow peak, indicating an isotropic (liquid) n-alkane component, likely due to shorter n-alkane molecules present in the sample. For C30d in DMPC, this component appears broader, and may originate from non-crystallized molecules. A more detailed discussion of this feature and the temperature dependence of the 2 H spectrum of C30d is provided in the following section.