The samples were packed into Kel-F MAS rotor inserts (Bruker, B4493), sealed with plugs and screws, and placed inside 4-mm ZrO 2 rotors with a Kel-F drive cap (Bruker, H14355). All NMR experiments were performed at 298 K sample temperature, unless otherwise stated, and kept stable at ±0.1 K with a Bruker BCU II-80/60 variable temperature unit (VTU) (Fällanden, Switzerland). The VTU was calibrated using MeOH-d4 (99.8%). 1 H and 13 C pulse calibration was done through nutation frequency experiments on the sample of interest spinning at 5 kHz. Adamantane spinning at 10 kHz was used as chemical shift reference for 1 H (1.85 ppm), and H 3 PO 4 for 31 P (0 ppm). Sample hydration was determined by 1 H MAS (Fig. ). Lipid phase was confirmed to be lamellar by the signal lineshape of static 31 P spectra. R-PDLF experiments R-type proton-detected local field (R-PDLF) recoupling experiments were recorded at 5 kHz spinning rate, using refocused insensitive nuclei enhancement by polarization transfer (rINEPT) for polarization transfer and 1 H broad-band decoupling during acquisition.