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Relaxivity and binding of Mn 2+ ions in solutions of phosphatidylserine vesicles
Author(s) -
Koenig Seymour H.,
Brown Rodney D.,
Kurland Robert,
Ohkit Shinpei
Publication year - 1988
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910070202
Subject(s) - ion , vesicle , phosphatidylserine , chemistry , crystallography , membrane , biophysics , biochemistry , phospholipid , organic chemistry , biology
We report the magnetic field dependence (NMRD profiles) of 1/ T 1 , of solvent protons in solutions of unilamellar phosphatidylserine vesicles with added Mn 2+ ions, including studies of the variation of the profiles with temperature, extent of coverage of available binding sites by Mn 2+ ions, ionic strength, and competition with (nonparamagnetic) Ca 2+ ions. In addition, we sketch the theory of screening of the negative surface charges of the vesicles due to both specific binding of Mn 2+ ions and nonspecific effects of other mobile solute ions. The major result is that the NMRD profiles, although qualitatively similar, vary systematically as the parameters of the solutions are altered, in a manner consistent with the theory of screening. The profiles of the Mn 2+ ‐vesicle complexes are much like those of Mn 2+ ‐protein complexes that have the ions in an octahedral ligand environment. In addition, we find that the profiles are similar to those reported for Mn 2+ ions in packed liver cells and liver tissue, supporting a previous conjecture that available Mn 2+ in liver binds to the polar head groups of cell membranes, saturating these sites before binding elsewhere. Again, it is evident that results for in vitro model systems can be extrapolated reliably to tissue behavior. © 1988 Academic Press, Inc.