Spin-echo decays of spin-labelled phospholipids have been recorded to study the chain dynamics in the low-temperature phases of dipalmitoyl phosphatidylcholine membranes with and without 50 mol% cholesterol. The phase-memory relaxation time, T2M, depends on the position of spin-labelling in the sn-2 chain, and on the presence of cholesterol. A biphasic temperature dependence of T2M is obtained over the range 150-270 K. Echo-detected field-swept absorption EPR spectra were recorded as a function of the echo delay time, . The echo-detected EPR lineshapes show a strong dependence on , revealing anisotropic phase relaxation arising from torsional chain motions. Cholesterol has a large effect on torsional oscillations about the chain long axis. Small-amplitude chain motions in the low temperature phases may be important for cryopreservation of membranes.
Chain dynamics in the low temperature phase of lipid membranes by Electron Spin Echo spectroscopy
BARTUCCI R.;GUZZI, Rita;
2003-01-01
Abstract
Spin-echo decays of spin-labelled phospholipids have been recorded to study the chain dynamics in the low-temperature phases of dipalmitoyl phosphatidylcholine membranes with and without 50 mol% cholesterol. The phase-memory relaxation time, T2M, depends on the position of spin-labelling in the sn-2 chain, and on the presence of cholesterol. A biphasic temperature dependence of T2M is obtained over the range 150-270 K. Echo-detected field-swept absorption EPR spectra were recorded as a function of the echo delay time, . The echo-detected EPR lineshapes show a strong dependence on , revealing anisotropic phase relaxation arising from torsional chain motions. Cholesterol has a large effect on torsional oscillations about the chain long axis. Small-amplitude chain motions in the low temperature phases may be important for cryopreservation of membranes.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
