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Molecular factors that determine Curie spin relaxation in dysprosium complexes
P Caravan1, M T Greenfield, J W Bulte
1EPIX Medical, Inc., Cambridge, Massachusetts 02142-1118, USA. pcaravan@epixmed.com
Magnetic Resonance in Medicine
|October 25, 2001
Summary
Dysprosium complexes enhance water proton relaxation. Inner-sphere water and binding to proteins significantly boost their efficiency as transverse relaxation (T2) agents.
Area of Science:
- Magnetic Resonance Imaging
- Inorganic Chemistry
- Biophysics
Background:
- Dysprosium complexes act as transverse relaxation (T2) agents for water protons.
- Mechanisms include chemical exchange and Curie spin relaxation.
Purpose of the Study:
- To investigate the role of inner-sphere water in dysprosium-based T2 agents.
- To elucidate the contribution of Curie spin relaxation and binding effects.
Main Methods:
- Utilized matched dysprosium(III) complexes (Dy-L1 with inner-sphere water, Dy-L2 without).
- Determined water exchange kinetics using Oxygen-17 Nuclear Magnetic Resonance ((17)O NMR).
- Investigated interactions with human serum albumin (HSA).
Main Results:
- Transverse relaxation of bulk water is primarily an inner-sphere effect.
- High-field relaxation by Dy-L1 is dominated by chemical shift differences.
- Binding to HSA significantly increases rotational correlation time (tau(R)) and Curie spin contribution.
- Transverse relaxivity (r2) increased 3-8 fold upon HSA binding.
Conclusions:
- Inner-sphere water is crucial for efficient T2 relaxation.
- Curie spin relaxation becomes significant with increased rotational correlation time.
- Design of novel dysprosium agents can be optimized by considering these factors for enhanced relaxivity.
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