Magnetic field dependence of spin-lattice relaxation enhancement using piperidinyl nitroxyl spin-labels |
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| Authors: | J D Lovin G E Wesbey B L Engelstad G Sosnovsky M Moseley D L Tuck R C Brasch |
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| Institution: | 1. Department of Radiology, University of Michigan, Ann Arbor, MI 48109 USA;2. Contrast Medium Laboratory, Department of Radiology, School of Medicine, University of California, San Francisco, CA 94143 USA;3. The Department of Chemistry, University of Wisconsin, Milwaukee, WI 53201, USA;4. The Department of Pharmaceutical Chemistry, School of Pharmacy, University of California, San Francisco, CA 94143 USA |
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| Abstract: | We examined the magnetic resonance properties of 12 paramagnetic piperidinyl nitroxyls in water and plasma solutions. Paramagnetic contributions to proton relaxation times were measured using 10.7 and 100 MHz spectrometers. Proton relaxation enhancement from nitroxyls increased with ascending molecular weight, in plasma solutions versus equimolar aqueous solutions, and with measurements at 10.7 MHz compared to 100 MHz. Relaxation rates were observed to approximately double at 10.7 MHz compared to 100 MHz and from water to plasma solutions. The data indicate that proton spin-lattice relaxation enhancement is magnetic field-dependent, and increases using nitroxyls of large molecular weight and with chemical substitutents that increase the microviscosity of solvent water molecules. The development of nitroxyls for diagnostic MRI will be aided by understanding these in vitro physical characteristics and trends. |
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| Keywords: | Nitroxyl spin labels Magnetic resonance contrast media Field-dependent relaxation |
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