129Xe NMR Spectroscopic Investigation of the Interaction of Xenon with Ions in Aqueous Solution

Characterization of the Effects of Nonspecific Xenon–Protein Interactions on 129Xe Chemical Shifts in Aqueous Solution: Further Development of Xenon as a Biomolecular Probe

“…Given the dilute solute concentrations for which this effect is observable, deshielding likely occurs through direct xenon-solute interactions which polarize the xenon electron cloud rather than through a solute-induced change in bulk water structure. This supposition is consistent with previous accounts of the deshielding effects of ions in aqueous solution (25). The deshielding effects of amino acids resulting from nonspecific xenon-solute interactions can be quantitatively understood in a manner consistent with previous models for 129 Xe chemical shifts that consider pairwise van der Waals interactions between xenon and solvent functional groups.…”

“…In solutions of metal cations and halide anions, diffusion-mediated interactions lead to a downfield shift relative to water that increases linearly with increasing salt concentration (25). The concentration-normalized chemical shift (here denoted α and expressed in units of ppm/mM) increases with ion charge, corresponding to a greater polarization of the xenon electron cloud.…”

Water soluble cucurbit[6]uril derivative as a potential Xe carrier for 129Xe NMR-based biosensors

“…The NMR signal of the bound Xe in the salt solution is shifted downfield com-pared with that in pure water, which is presumably caused by the interactions between the encapsulated Xe and the cations on the portals. 14 In this case, the population of the bound xenon is smaller than that of free xenon, opposite to the situation in pure water, indicating that the binding affinity of CB*[6] for xenon in the salt solution is smaller than that in pure water. The binding constant for the complexation of xenon with CB*[6] in aqueous Na 2 SO 4 solution was determined to be 180 M À1 by integrating the signals of the free and bound species (total [Xe] ¼ 0.76 mM).…”

Probing Reversible Guest Binding with Hyperpolarized 129Xe-NMR: Characteristics and Applications for Cucurbit[n]urils

“…Due to line broadening, a more accurate determination of the binding constant of the water soluble CB [6] was not possible. It was thus also measured in the presence of 0.2 M Na 2 SO 4 and both signals were shifted downfield, presumably due to the interactions between the encapsulated Xe and the cations on the portals [136]. These cations also decelerate the exchange and limit the line broadening, thereby revealing a binding constant for Xe with the water-soluble CB [6] of 180 M −1 .…”