Lipid polymorphism and hydrocarbon order

1990 ◽  
Vol 68 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Michel Lafleur ◽  
Myer Bloom ◽  
Pieter R. Cullis
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Hexagonal Phase ◽  
Orientational Order ◽  
Lipid Phase ◽  
Nonbilayer Lipids ◽  
Acyl Chains ◽  
Lipid Polymorphism ◽  
Phase Symmetry ◽  
Nuclear Magnetic

The use of 2H nuclear magnetic resonance for the characterization of the polymorphic behavior of lipids is illustrated. Different lipid phase preferences may be expected to influence the orientational order and its variation along the acyl chains. Several results are presented to support that view. An increase of motional freedom and a redistribution of the order along the acyl chains are observed during the lamellar-to-hexagonal phase transition, showing that the order profile is sensitive to the lipid phase symmetry. In addition, if the preferences for nonlamellar phases are not expressed explicitly, the presence of "nonbilayer" lipids constrained in bilayer environment induces increased hydrocarbon order. This suggests that order parameters of the acyl chains and lipid polymorphic tendencies are intimately related.Key words: lipid, polymorphism, 2H nuclear magnetic resonance, hydrocarbon order.

Anesthetic-membrane interaction: A 2H nuclear magnetic resonance study of the binding of specifically deuterated tetracaine and procaine to phosphatidylcholine

1984 ◽  
Vol 62 (2-3) ◽  
pp. 178-184 ◽  
Author(s):  
Eric C. Kelusky ◽  
Ian C. P. Smith
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Local Anesthetics ◽  
Nuclear Magnetic Resonance Study ◽  
Weakly Bound ◽  
Slow Exchange ◽  
H Nmr ◽  
Line Shapes ◽  
Acyl Chains ◽  
Nuclear Magnetic

The binding of the local anesthetics tetracaine and procaine with multilamellar dispersions of egg phosphatidylcholine has been studied by 2H nuclear magnetic resonance (NMR). The 2H-NMR line shapes of specifically deuterated local anesthetics are found to be very dependent on the attainment of a true equilibrium. The equilibrium could be most properly reached by the use of repeated freeze–thaw–vortex cycles. The data for tetracaine are consistent with the three-site exchange model proposed earlier. Tetracaine is in slow exchange between a strongly bound site and a weakly bound site and in fast exchange between the weakly bound site and free in solution. The slow exchange rate is estimated, from temperature and dilution studies, to be approximately 1.5 × 103 s−1 at pH 5.5 and slightly faster at pH 9.5. Comparisons of the quadrupole splittings with those seen for our earlier work in egg phosphatidylethanolamine suggest that the location of the strongly bound site in phosphatidylcholine is dependent on the anesthetic charge. This is in contrast to egg phosphatidylethanolamine, where molecular shapes appear to be the determining factor for the location of the anesthetic. Procaine bound very weakly to the model membranes, to yield only a broad resonance and no quadrupole splitting. It appears that procaine, unlike tetracaine, is not bound by the ordered acyl chains.

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