No abstract

Caged in: The formation of a complex between a peptide ligand and a major histocompatibility complex (MHC) class II protein is detected by a (129)Xe biosensor. Cryptophane molecules that trap Xe atoms are modified with a hemagglutinin (HA) peptide, which binds to the MHC protein. The interaction can be monitored by an NMR chemical shift change of cage-HA bound (129)Xe.

A stand-alone, self-contained and transportable system for the polarization of 129Xe by spin exchange optical pumping with Rb is described. This mobile polarizer may be operated in batch or continuous flow modes with medium amounts of hyperpolarized 129Xe for spectroscopic or small animal applications. A key element is an online nuclear magnetic resonance module which facilitates continuous monitoring of polarization generation in the pumping cell as well as the calculation of the absolute 129Xe polarization. The performance of the polarizer with respect to the crucial parameters temperature, xenon and nitrogen partial pressures, and the total gas flow is discussed. In batch mode the highest 129Xe polarization of PXe = 40 % was achieved using 0.1 mbar xenon partial pressure. For a xenon flow of 6.5 and 26 mln/min, PXe = 25 % and PXe = 13 % were reached, respectively. The mobile polarizer may be a practical and efficient means to make the applicability of hyperpolarized 129Xe more widespread.