2H NMR studies of isomeric omega 3 and omega 6 polyunsaturated phospholipid membranes.
The properties of aqueous multilamellar dispersions of [2H31]16:0-alpha 18:3 PC (1-[2H31]palmitoyl-2-cis,cis,cis-octa-9,12,15- trienoylphosphatidylcholine) and of [2H31]16:0-gamma 18:3 PC (1-[2H31]palmitoyl-2-cis,cis,cis-octa-6,9,12-trienoylphosphatid ylcholine) were compared by broadline 2H NMR spectroscopy. These isomeric phospholipids differ only in the location of the unsaturations in the sn-2 chain. The alpha 18:3 chain has double bonds at delta 9, 12, and 15 positions whereas in the gamma 18:3 chain they are at positions delta 6, 9, and 12. Moment analysis of spectra recorded as a function of temperature reveals dramatically distinct phase behavior for the two isomers. The gel to liquid crystalline transition for [2H31]16:0-alpha 18:3 PC membranes exhibits broad hysteresis which is characterized by a mid point temperature of -9 degrees C and -20 degrees C on heating and cooling, respectively. In contrast, the phase transition of [2H31]16:0-gamma 18:3 PC membranes does not exhibit hysteresis and occurs over a lower temperature range centred on -27 degrees C. Appreciably different molecular ordering also exists within the membranes in the liquid crystalline state. Average order parameters SCD are smaller in [2H31] 16:0-alpha 18:3 PC than in [2H31]16:0-gamma 18:3 PC by 10% at the same temperature and by 20% at equal reduced temperature. Smoothed order parameter profiles generated from depaked spectra clarify the nature of the difference.(ABSTRACT TRUNCATED AT 250 WORDS)
McCabe
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MA
Department of Physics, Indiana University-Purdue University Indianapolis 46202-3273.
Griffith
G L
GL
Ehringer
W D
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Stillwell
W
W
Wassall
S R
SR
D003903:Deuterium; D015525:Fatty Acids, Omega-3 / Q000737:chemistry*; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated / Q000737:chemistry*; D007536:Isomerism; D008051:Lipid Bilayers; D009682:Magnetic Resonance Spectroscopy; D008563:Membrane Lipids / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry*; D013696:Temperature
D015525:Fatty Acids, Omega-3; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated; D008051:Lipid Bilayers; D008563:Membrane Lipids; D010743:Phospholipids; D003903:Deuterium