Caffeine modulates the dynamics of DODAB membranes: Role of the physical state of the bilayer

Caffeine (1,3,7-trimethylxanthine), an ingredient of coffee, is used worldwide as a psychostimulant, antioxidant, and adjuvant analgesic. To gain insights into the action mechanism of caffeine, we report on its effects on the microscopic dynamics of a dioctadecyldimethylammonium bromide lipid membrane, as studied using quasielastic neutron scattering. Caffeine significantly modulates the microscopic dynamics of the lipids in the system, and the effects depend on the lipid phase. In the coagel phase, caffeine acts as a plasticizing agent, whereas in the fluid phase, it restricts the lateral and internal motions of the lipids. The present study illustrates how caffeine regulates the fluidity of the membrane by modulating the dynamics of constituent lipids depending on the physical state of the bilayer.