Chain dynamics in the low-temperature phases of lipid membranes by electron spin-echo spectroscopy.
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, T(2M), depends on the position of spin-labelling in the sn-2 chain, and on the presence of cholesterol. A biphasic temperature dependence of T(2M) 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, tau. The echo-detected EPR lineshapes show a strong dependence on tau, 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.
Bartucci
Rosa
R
Dipartimento di Fisica, Università della Calabria, I-87036 Arcavacata di Rende (CS), Italy. bartucci@fis.unical.it
Guzzi
Rita
R
Marsh
Derek
D
Sportelli
Luigi
L
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000378:metabolism*; D016880:Anisotropy; D002784:Cholesterol / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D008051:Lipid Bilayers / Q000378:metabolism*; D013696:Temperature
D008051:Lipid Bilayers; D015060:1,2-Dipalmitoylphosphatidylcholine; D002784:Cholesterol