Required amounts of POPC in chloroform solution (Avanti Polar Lipids, Birmingham, AL, USA) were moved into a weighed Eppendorf tube and freeze-dried overnight to completely remove the solvent. The Eppendorf with the dried lipid was weighed again, the desired amount of deionized water added with Ar(g) bubbling (plus 1-2 µl), and the sample allowed to swell (40°C, 30 ′ ). Then the sample was mechanically mixed using a thin polished stainless steel rod, the Eppendorf closed with Parafilm to prevent evaporation, and let to equilibrate (40°C, 24 h). The sample then was mixed again and equilibration continued for 48 h, after which samples were packed into Kel-F MAS rotor inserts (Bruker, B4493) by inserting a 100-µl tip into the insert and centrifuging (1 000 g, 5 ′ ). Packed and sealed inserts were stored at 4°C before being measured. For effective packing of the samples in the inserts, we targeted to have approximately 40-50 mg of each sample in total (exceeding the amount needed to fill the whole volume of the insert), taking into account some material loss when transferring the sample from the Eppendorf tube to the inserts.