Dynamics of dioleoyl phosphatidylcholine by muon spin relaxation

Muon spin relaxation has been used to study the dynamics of the hydrocarbon chains in methyl oleate and dioleoyl phosphatidylcholine (DOPC) as a function of temperature. Repolarisation of the radical muonium spin shows that the muons implant in the C-9-C-10 double bond. Dynamic processes involving the hydrocarbon chains are evident from the increases observed in the muon spin relaxation rate as the ester and DOPC are heated from 100 to 400 K. Similar increases in muon spin relaxation are observed before the melting point in methyl oleate and the chain melting temperature in DOPC indicative of fast segmental motions occurring in the chains before the phase change takes place.