Hyperpolarized 129Xe chemical exchange saturation transfer (Hyper-CEST) NMR is a powerful technique for the ultra-sensitive detection of Xe host molecules (e.g., cryptophane-A). Saturating at the appropriate Xe@cryptophane resonance frequency results in rapid relaxation of the 129Xe hyperpolarization in bulk solution. The cryptophane effectively catalyzes this process by providing a unique molecular environment for spin depolarization, while allowing numerous xenon exchanges with the bulk solution within the relaxation lifetime, T1 ~ 1 min. Following these principles, a tri-acetic-acid cryptophane-A derivative (TAAC) was indirectly detected at 1.4 picomolar concentration, which is the record for a single-unit xenon host. To investigate this sensitivity enhancement, the xenon binding kinetics of TAAC in water was studied by customized EXSY measurement. At 297 K, texch was 22 � 3 ms. At 320 K, the rate of 129Xe depolarization catalyzed by TAAC in the presence of RF pulses, kcat, was estimated to be 9 x 105 s-1.

Picomolar sensitivity <sup>129</sup>Xe Hyper-CEST NMR with a water-soluble cryptophane

244th National Meeting (2012)

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Picomolar sensitivity 129Xe Hyper-CEST NMR with a water-soluble cryptophane

Picomolar sensitivity ¹²⁹Xe Hyper-CEST NMR with a water-soluble cryptophane