Enhancing 31P NMR relaxation rates with a kinetically inert gadolinium complex

Abstract

The kinetically stable heptadentate gadolinium complex Gd.pDO3A (1.Gd) demonstrates significant ³¹P nuclear magnetic resonance (NMR) relaxation enhancement of biologically relevant phosphate species; adenosine triphosphate (ATP), phosphocreatine (PCr) and inorganic phosphate. Gd.pDO3A (1.Gd) binds these species in fast exchange, enabling the relaxation of the bulk phosphate species in solution. This gives rise to ³¹P relaxation enhancements up to 250-fold higher than those observed for ³¹P relaxation enhancements with the commercial MRI contrast agent Gd.DOTA (DOTAREM), 2. Gd.pDO3A-like complexes may have potential applications as ³¹P magnetic resonance contrast agents, since shortening the T₁ relaxation time of phosphate species would reduce the time needed to acquire ³¹P-MR spectra.