Report No xxxx - Instytut Fizyki JÄ drowej PAN

EFFECT OF TEMPERATURE ON LIPOSOME STRUCTURES.
EPR AND NMR STUDIES
Danuta Pentak 1 , Wioletta Korus 1 , Anna Sułkowska 2 , Wiesław W. Sułkowski 1
1 Department of Environmental Chemistry and Technology, University of Silesia,
Szkolna 9, 40-006 Katowice, Poland; 2 Department of Physical Pharmacy, Medical University
of Silesia, Jagiellońska 4, 41-200 Sosnowiec, Poland
The effect of temperature on liposomes structures has been investigated by means of
electron paramagnetic resonance spectroscopy using spin labeling technique and NMR
spectroscopy. The EPR spectra were recorded on a Bruker EMX spectrometer in the
temperature range 300 – 340K. The 1 H-NMR, 13 C-NMR and 31 P-NMR spectra were recorded
on a Bruker 400 MHz spectrometer in the same temperatures. Liposomes were prepared from
L-α-phosphatidylcholine dipalmitoyl (1,2-dihexadecanoyl-sn-glycerol-3-phosphocholine)
(DPPC) and cholesterol (5-cholesten-3β-ol) as main component of a membrane. Liposomes
contained variable quantity of cholesterol. Molar ratio of DPPC to cholesterol was: 4:1, 4:0,5,
4:0. The spin marker, 2-(3carboxypropyl)-4,4-dimethyl-2-tridecyl-3-oxazolidinyloxyl free
radical (5-DOXYL), placed in a liposome membrane, allows to observe the structural changes
in liposomes with temperature increasing. The correlation time and an order parameter of the
5-DOXYL spin marker placed in liposomes membranes were determined. The changes of
rotational correlation time and order parameter values with increasing temperature result from
the motion rise of the spin probe. The intensity of the EPR signal of 5-DOXYL and NMR
spectroscopy give information about structure of liposomes.
71