%0 Journal Article %J Journal of Magnetic Resonance %D 2010 %T Xenon-based molecular sensors in lipid suspensions %A Meldrum, T. %A Schroder, L. %A Denger, P. %A Wemmer, D. E. %A Pines, A. %K binding %X

There have been many proposals to use xenon-based molecular sensors in biological settings. Fundamental to understanding the properties of these sensors in vivo is characterizing their behavior in lipid environments. We report the investigation of xenon-based molecular sensors in suspensions of lipid vesicles with a size comparable to cells. We detail spectroscopic properties of sensors associated with lipid vesicles as well as those in equilibrium in the surrounding solution. We characterize the dependence of the spectral parameters on temperature, relevant for studies at physiological temperatures. We also demonstrate the ability to perform selective saturation transfer (Hyper-CEST) between sensor, both lipid bound and unbound, and the bulk solution. Lastly, we demonstrate the applicability of saturation transfer in the heterogeneous medium as an imaging modality. (C) 2010 Elsevier Inc. All rights reserved.

%B Journal of Magnetic Resonance %V 205 %P 242-246 %8 Aug %@ 1090-7807 %G English %U ://WOS:000280064500008 %N 2 %M WOS:000280064500008 %! Xenon-based molecular sensors in lipid suspensions %R Doi 10.1016/J.Jmr.2010.05.005 %0 Journal Article %J Proceedings of the National Academy of Sciences of the United States of America %D 2000 %T Evidence of nonspecific surface interactions between laser-polarized xenon and myoglobin in solution %A Rubin, S. M. %A Spence, M. M. %A Goodson, B. M. %A Wemmer, D. E. %A Pines, A. %K binding %X

The high sensitivity of the magnetic resonance properties of xenon to its local chemical environment and the large Xe-129 NMR signals attainable through optical pumping have motivated the use of xenon as a probe of macromolecular structure and dynamics. In the present work, we report evidence for nonspecific interactions between xenon and the exterior of myoglobin in aqueous solution, in addition to a previously reported internal binding interaction. Xe-129 chemical shift measurements in denatured myoglobin solutions and under native conditions with varying xenon concentrations confirm the presence of nonspecific interactions. Titration data are modeled quantitatively with treatment of the nonspecific interactions as weak binding sites. Using laser-polarized xenon to measure Xe-129 spin-lattice relaxation times (T-1), we observed a shorter T-1 in the presence of 1 mM denatured apomyoglobin in 6 M deuterated urea (T-1 = 59 +/- 1 s) compared with that in 6 M deuterated urea alone (T-1 = 291 +/- 2 s), suggesting that nonspecific xenon-protein interactions can enhance Xe-129 relaxation. An even shorter T1 was measured in ? mM apomyoglobin in D2O (T-1 = 15 +/- 0.3 s), compared with that in D2O alone (T-1 = 506 +/- 5 s). This difference in relaxation efficiency likely results from couplings between laser-polarized xenon and protons in the binding cavity of apomyoglobin that may permit the transfer of polarization between these nuclei via the nuclear Overhauser effect.

%B Proceedings of the National Academy of Sciences of the United States of America %V 97 %P 9472-9475 %8 Aug 15 %@ 0027-8424 %G English %U ://WOS:000088840500026 %N 17 %M WOS:000088840500026 %! Evidence of nonspecific surface interactions between laser-polarized xenon and myoglobin in solution %R Doi 10.1073/Pnas.170278897