The promising dynamic nuclear polarization (DNP) for hyperpolarized ¹³C‐MRI/MRS of real‐time metabolism in vivo is challenged by the limited number of agents with the required physical and biological properties. The physical requirement of a liquid‐state T₁ of tens of seconds is mostly found for ¹³C‐carbons in small molecules that have no direct protons attached, i.e. carbonyl, carboxyl and certain quaternary carbons. Unfortunately, such carbon positions do not exist in a large number of metabolic agents, and chemical shift dispersion often limits detection of their chemical evolution. We have previously shown that direct deuteration of protonated carbon positions significantly prolongs the ¹³C T₁ in the liquid state and provides potential ¹³C‐labeled agents with differential chemical shift with respect to metabolism. The Choline Molecular Probe [1,1,2,2‐D₄, 2‐¹³C]choline chloride (CMP2) has recently been introduced as a means of studying choline metabolism in a hyperpolarized state. Here, the biophysical properties of CMP2 were characterized and compared with those of [1‐¹³C]pyruvate to evaluate the impact of molecular probe deuteration. The CMP2 solid‐state polarization build‐up time constant (30 min) and polarization level (24%) were comparable to those of [1‐¹³C]pyruvate. Both compounds' liquid state T₁ increased with temperature. The high‐field T₁ of CMP2 compared favorably with [1‐¹³C]pyruvate. Thus, a deuterated agent demonstrated physical properties comparable to a hyperpolarized compound of already proven value, whereas both showed chemical shift dispersion that allowed monitoring of their metabolism. It is expected that the use of deuterated carbon‐13 positions as reporting hyperpolarized nuclei will substantially expand the library of agents for DNP‐MR. Copyright © 2011 John Wiley & Sons, Ltd.

The dissolution-dynamic nuclear polarization technology had previously enabled nuclear magnetic resonance detection of various nuclei in a hyperpolarized state. Here, we show the hyperpolarization of ³¹P nuclei in important biological phosphates (inorganic phosphate and phosphocreatine) in aqueous solutions. The hyperpolarized inorganic phosphate showed an enhancement factor >11,000 (at 5.8 T, 9.3% polarization) in D₂O (T₁ 29.4 s). Deuteration and the solution composition and pH all affected the lifetime of the hyperpolarized state. This capability opens up avenues for real-time monitoring of phosphate metabolism, distribution, and pH sensing in the live body without ionizing radiation. Immediate changes in the microenvironment pH have been detected here in a cell-free system via the chemical shift of hyperpolarized inorganic phosphate. Because the ³¹P nucleus is 100% naturally abundant, future studies on hyperpolarized phosphates will not require expensive isotope labeling as is usually required for hyperpolarization of other substrates.