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Interactions of nitroxides with plasma and blood: Effect on 1/ T 1 of water protons
Author(s) -
Bennett Harold F.,
Brown Rodney D.,
Keana John F. W.,
Koenig Seymour H.,
Swartz Harold M.
Publication year - 1990
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.1910140106
Subject(s) - nitroxide mediated radical polymerization , chemistry , rotational correlation time , molecule , relaxation (psychology) , membrane , aqueous solution , radical , electron paramagnetic resonance , hydrogen bond , biophysics , nuclear magnetic resonance , organic chemistry , biochemistry , psychology , social psychology , physics , radical polymerization , biology , polymer , copolymer
Nitroxide stable free radicals (nitroxides) have potential utility as MRI contrast‐enhancing agents with the additional capability of reflecting redox metabolism. In order to gain a better understanding of their potential interactions in vivo , we have studied the longitudinal NMRD profiles (1 / T 1 as a function of field strength) and ESR spectra for lipophilic and aqueous‐soluble nitroxides in blood, plasma, and plasma components. Typical water‐soluble nitroxides do not interact appreciably with blood, plasma, or plasma proteins. Fatty acid nitroxides do interact physically with blood, predominantly by intercalation within red blood cell membranes and binding to albumin. The latter interaction results in significantly enhanced relaxivity for the nitroxide/HSA complex. Relaxation of water protons in this case is dominated by inner sphere processes, ostensibly due to water molecules hydrogen bonded to nitroxide moieties. The rotational reorientation time for the complex, the electronic relaxation time, and the exchange time for the water molecule reversably bound to the nitroxide, all appear significantly to influence the correlation time (∼ 16 ns) for this inner sphere contribution. Inc. © 1990 Academic Press, Inc.