  Heat-bath cooling is a component of practicable algorithmic cooling of spins,
an approach which might be useful for in vivo 13C spectroscopy, in particular
for prolonged metabolic processes where substrates that are hyperpolarized
ex-vivo are not effective. We applied heat-bath cooling to 1,2-13C2-amino
acids, using the alpha protons to shift entropy from selected carbons to the
environment. For glutamate and glycine, both carbons were cooled by about
2.5-fold, and in other experiments the polarization of C1 nearly doubled while
all other spins had equilibrium polarization, indicating reduction in total
entropy. The effect of adding Magnevist, a gadolinium contrast agent, on
heat-bath cooling of glutamate was investigated.
