Distinctive pressure effects on partitioning and rotational motions of nitroxide spin probes in dispersions of a triglyceride membrane

The effects of pressure were examined for the partitioning and rotational correlation time of nitroxide probes, TEMPO and DTBN, in dispersions of a triglyceride membrane. As external pressures increased, nitroxide probes shifted from the vesicle phase to the aqueous phase. Rotational correlation times of TEMPO and DTBN in the vesicle phase, determined from ESR line broadening, increased remarkably with increasing pressure, dependent of the molecular size of the nitroxide probes: ΔV‡ = 65.6 cm3 mol−1 for TEMPO and 24.4 cm3 mol−1 for DTBN. Based on the results, the microscopic properties inside the triglyceride membrane are discussed.