Characterizing the magnetic susceptibility tensor of lanthanide-containing polymethylated-DOTA complexes

Lanthanide complexes based on the DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) cage are commonly used as phase contrast agents in magnetic resonance imaging, but can also be utilized in structural NMR applications due to their ability to induce either paramagnetic relaxation enhan...

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Bibliographic Details
Published in:Journal of biomolecular NMR 2016-10, Vol.66 (2), p.125-139
Main Authors: Strickland, Madeleine, Schwieters, Charles D., Göbl, Christoph, Opina, Ana C. L., Strub, Marie-Paule, Swenson, Rolf E., Vasalatiy, Olga, Tjandra, Nico
Format: Article
Language:English
Subjects:
Biochemistry
Biological and Medical Physics
Biophysics
Heterocyclic Compounds, 1-Ring - chemistry
Hydrogen-Ion Concentration
Lanthanoid Series Elements - chemistry
Magnetic Resonance Spectroscopy - methods
Metals - chemistry
Methylation
Models, Molecular
Molecular Conformation
Molecular Structure
Physics
Physics and Astronomy
Spectroscopy/Spectrometry
Temperature
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Summary:Lanthanide complexes based on the DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) cage are commonly used as phase contrast agents in magnetic resonance imaging, but can also be utilized in structural NMR applications due to their ability to induce either paramagnetic relaxation enhancement or a pseudocontact shift (PCS) depending on the choice of the lanthanide. The size and sign of the PCS for any given atom is determined by its coordinates relative to the metal center, and the characteristics of the lanthanide’s magnetic susceptibility tensor. Using a polymethylated DOTA tag (Ln-M8-SPy) conjugated to ubiquitin, we calculated the position of the metal center and characterized the susceptibility tensor for a number of lanthanides (dysprosium, thulium, and ytterbium) under a range of pH and temperature conditions. We found that there was a difference in temperature sensitivity for each of the complexes studied, which depended on the size of the lanthanide ion as well as the isomeric state of the cage. Using 17 O-NMR, we confirmed that the temperature sensitivity of the compounds was enhanced by the presence of an apically bound water molecule. Since amide-containing lanthanide complexes are known to be pH sensitive and can be used as probes of physiological pH, we also investigated the effect of pH on the Ln-M8-SPy susceptibility tensor, but we found that the changes in this pH range (5.0–7.4) were not significant.
ISSN:0925-2738
1573-5001
DOI:10.1007/s10858-016-0061-x