ISSN:
1432-1017
Keywords:
Oxygen-Solubility
;
Lipid bilayers
;
NMR relaxation
;
Defect structure
;
NMR second moment
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Physics
Notes:
Abstract A method is described that allows to determine the oxygen concentration in microscopic subphases, such as lipid bilayers, by measuring the enhancement of NMR spin-lattice relaxation (T 1) caused by paramagnetic oxygen. The presence of oxygen itself provides the measuring effect, which has the advantage of the lack of any distortions by large probe molecules in the system. The T 1-jump of the water protons of a dipalmitoyl lecithin (DPL)/water-dispersion at the phase transition yields information about the O2-solubility in the DPL bilayers. The results can be interpreted in a straightforward way in terms of a two phase model DPL/H2O. The measurements indicate, however, that a more appropriate approach is possible if a three-phase system DPL/bound water/free water is taken into account. The O2-partition coefficients and the free enthalpies of solution are evaluated for all subsystems in both models. The oxygen solubility in paraffin chains is obviously connected to the defect structure. A comparison is drawn between n-paraffins and the DPL fatty-acid chains. The gel-state of DPL lamellae does not correspond to the crystalline paraffin state, but rather to the more disordered rotator-phase. To emphasize this, NMR second moment data of DPL and some n-alkanes are compared.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00538841
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