%0 Journal Article %J Journal of the American Chemical Society %D 2010 %T A Xenon-Based Molecular Sensor Assembled on an MS2 Viral Capsid Scaffold %A Meldrum, T. %A Seim, K. L. %A Bajaj, V. S. %A Palaniappan, K. K. %A Wu, W. %A Francis, M. B. %A Wemmer, D. E. %A Pines, A. %K nmr %X

In MRI, anatomical structures are most often differentiated by variations in their bulk magnetic properties. Alternatively, exogenous contrast agents can be attached to chemical moieties that confer affinity to molecular targets; the distribution of such contrast agents can be imaged by magnetic resonance. Xenon-based molecular sensors are molecular imaging agents that rely on the reversible exchange of hyperpolarized xenon between the bulk and a specifically targeted host-guest complex. We have incorporated similar to 125 xenon sensor molecules in the interior of an MS2 viral capsid, conferring multivalency and other properties of the viral capsid to the sensor molecule. The resulting signal amplification facilitates the detection of sensor at 0.7 pM, the lowest to date for any molecular imaging agent used in magnetic resonance. This amplification promises the detection of chemical targets at much lower concentrations than would be possible without the capsid scaffold.

%B Journal of the American Chemical Society %V 132 %P 5936-+ %8 May 5 %@ 0002-7863 %G English %U ://WOS:000277158500007 %N 17 %M WOS:000277158500007 %! A Xenon-Based Molecular Sensor Assembled on an MS2 Viral Capsid Scaffold %R Doi 10.1021/Ja100319f %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 Journal of the American Chemical Society %D 2006 %T Xenon biosensor amplification via dendrimer-cage supramolecular constructs %A Mynar, J. L. %A Lowery, T. J. %A Wemmer, D. E. %A Pines, A. %A Frechet, J. M. J. %K chemistry %B Journal of the American Chemical Society %V 128 %P 6334-6335 %8 May 17 %@ 0002-7863 %G English %U ://WOS:000237590400033 %N 19 %M WOS:000237590400033 %! Xenon biosensor amplification via dendrimer-cage supramolecular constructs %R Doi 10.1021/Ja061735s %0 Journal Article %J Actualite Chimique %D 2005 %T Xenon NMR as a probe for microporous and mesoporous solids, polymers, liquid crystals, solutions, flames, proteins, imaging %A Bartik, K. %A Choquet, P. %A Constantinesco, A. %A Duhamel, G. %A Fraissard, J. %A Hyacinthe, J. N. %A Jokisaari, J. %A Locci, E. %A Lowery, T. J. %A Luhmer, M. %A Meersmann, T. %A Moudrakovski, I. L. %A Pavlovskaya, G. E. %A Pierce, K. L. %A Pines, A. %A Ripmeester, J. A. %A Telkki, V. V. %A Veeman, W. S. %K silica-gels %X

We present in this paper some examples of the applications of the Nuclear Magnetic Resonance (NMR) of xenon used as a probe in the study of different chemical environments: determination of the porosity of micro-and mesoporous solids, evaluation of the concentrations and sizes of amorphous domains in solid polymers, characterization of liquid crystals, study of combustion processes at high temperature, determination of the structure and dynamics of organic systems and proteins in solution, assessment of cerebral blood flow.

%B Actualite Chimique %P 16-34 %8 Jun %@ 0151-9093 %G English %U ://WOS:000230991500005 %M WOS:000230991500005 %! Xenon NMR as a probe for microporous and mesoporous solids, polymers, liquid crystals, solutions, flames, proteins, imaging %0 Journal Article %J Chemistry of Materials %D 1995 %T Xe-129 Nmr-Studies of Hyper-Cross-Linked Polyarylcarbinols - Rigid Versus Flexible Structures %A Urban, C. %A Mccord, E. F. %A Webster, O. W. %A Abrams, L. %A Long, H. W. %A Gaede, H. %A Tang, P. %A Pines, A. %K adsorption %X

Xenon NMR is used with adsorption measurements to infer information about the microstructure of some novel hyper-cross-linked polyarylcarbinols. It is shown that rigidrod connecting units are necessary for microporosity in these systems, as hyper-cross-linked polymers based on flexible structures are found to have conventional surface areas and xenon NMR spectra. A microporous polymer based on rigid triarylcarbinol monomers shows high xenon uptake and a linear chemical shift variation with pressure at room temperature. Spin-lattice relaxation and cross-polarization dynamics are studied at low temperatures. In this regime the xenon has extremely long equilibration times, and the adsorption dynamics are complicated but give important insight into the polymer topology. The data are compared with two possible models of the polymer microstructwre.

%B Chemistry of Materials %V 7 %P 1325-1332 %8 Jul %@ 0897-4756 %G English %U ://WOS:A1995RK99300008 %N 7 %M WOS:A1995RK99300008 %! Xe-129 Nmr-Studies of Hyper-Cross-Linked Polyarylcarbinols - Rigid Versus Flexible Structures %R Doi 10.1021/Cm00055a008 %0 Journal Article %J Journal of Physical Chemistry %D 1995 %T Xenon Nmr-Study of a Nematic Liquid-Crystal Confined to Cylindrical Submicron Cavities %A Long, H. W. %A Luzar, M. %A Gaede, H. C. %A Larsen, R. G. %A Kritzenberger, J. %A Pines, A. %A Crawford, G. P. %K mixtures %X

NMR studies of xenon gas dissolved in the liquid crystal ZLI 1132 confined to submicron cylindrical cavities are reported. Spectra taken as a function of temperature yield a clear indication of the nematic to isotropic phase transition of the confined liquid crystals. In the nematic phase at 21 degrees C, the resonance line of dissolved Xe-129 exhibits a chemical shift anisotropy of 15 ppm due to a random distribution of director axes in the plane perpendicular to the long axis of the cylinder. The anisotropy and temperature dependence of the confined system are compared to control experiments that use the bulk liquid crystal. The quadrupolar splitting observed in the Xe-131 NMR spectrum of the confined liquid crystalline solution of xenon gas is slightly greater than that found in the bulk. Two-dimensional exchange NMR demonstrates that the xenon atoms probe different average liquid crystal directors within a single cavity on a 20 ms time scale and that interpore exchange occurs on a time scale of 400 ms. The exchange data indicate that changes in the orientation of the director within individual cavities occur on a length scale of about 2 mu m.

%B Journal of Physical Chemistry %V 99 %P 11989-11993 %8 Aug 3 %@ 0022-3654 %G English %U ://WOS:A1995RM90100029 %N 31 %M WOS:A1995RM90100029 %! Xenon Nmr-Study of a Nematic Liquid-Crystal Confined to Cylindrical Submicron Cavities %R Doi 10.1021/J100031a029 %0 Journal Article %J Journal of Physical Chemistry %D 1994 %T Xe-129 Nmr-Study of Tio2 (Anatase)-Supported V2o5 Catalysts %A Kritzenberger, J. %A Gaede, H. C. %A Shore, J. S. %A Pines, A. %A Bell, A. T. %K nay zeolite %X

TiO2 (anatase), V2O5, and V2O5/TiO2 (anatase) catalysts with 1.3%, 3.0%, and 9.8% weight loadings of V2O5 have been studied using temperature-dependent xenon-129 NMR spectroscopy. The intrinsic chemical shift values due to the interaction of xenon with the surface are 109 +/- 3 ppm for TiO2 (anatase) and 93 +/- 5 ppm for V2O5. The V2O5/TiO2 catalysts provide strong adsorption sites for xenon which cause an initial decrease of the chemical shift values at low xenon loadings. Additionally, the spectra of pure V2O5 reveal two distinct environments for the xenon atoms, consistent with the hysteresis of the isotherm and the existence of pores. Two-dimensional exchange spectroscopy was used to measure the rates and activation energy of xenon moving between these two environments.

%B Journal of Physical Chemistry %V 98 %P 10173-10179 %8 Oct 6 %@ 0022-3654 %G English %U ://WOS:A1994PK74000037 %N 40 %M WOS:A1994PK74000037 %! Xe-129 Nmr-Study of Tio2 (Anatase)-Supported V2o5 Catalysts %R Doi 10.1021/J100091a037