@article {295, title = {Diastereomeric Xe chemical shifts in tethered cryptophane cages}, journal = {Journal of the American Chemical Society}, volume = {128}, year = {2006}, note = {J Am Chem Soc118KQTimes Cited:14Cited References Count:42}, month = {Dec 27}, pages = {16980-16988}, abstract = {

Cryptophane cages serve as host molecules to a Xe atom. Functionalization of cryptophane-A has permitted the development of Xe as a biosensor. Synthetic routes used to prepare cryptophanes result in racemic mixtures of the chiral cages. In the preparation of a tethered cryptophane-A cage for biosensor applications, some achiral and chiral substituents such as left-handed amino acids have been used. When the substituent is achiral, the NMR signal of the Xe atom in the functionalized cage in solution is a single isotropic peak, since the Xe shielding tensor components in the R and L cages differ by no more than the signs of the off-diagonal elements. Chiral substituents can split the cage-encapsulated Xe NMR signal into one or more sets of doublets, depending on the number of asymmetric centers in the substituent. We carry out quantum mechanical calculations of Xe nuclear magnetic shielding for the Xe atom at the same strategic position within an L cryptophane-A cage, under the influence of chiral potentials that represent for r or I substituents outside the cage. Calculations of the Xe shielding response in the Lr and LI diastereomeric pairs permit the prediction of the relative order of the Xe chemical shifts in solutions containing the RI and LI diastereomers. Where the substituent itself possesses two chiral centers, comparison of the calculated isotropic shielding responses in the Llr, Lrl, RIl, and Lrr systems, respectively, permits the prediction of the Xe spectrum of diastereomeric systems in solutions containing Llr, RIr, LIl, and RIl systems. Assignment of the peaks observed in the experimental Xe NMR spectra is therefore possible, without having to undertake the difficult synthetic route that produces a single optically pure enantiomer.

}, keywords = {chirality}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja066661z}, url = {://WOS:000242941600104}, author = {Ruiz, E. J. and Sears, D. N. and Pines, A. and Jameson, C. J.} } @article {299, title = {Optimization of xenon biosensors for detection of protein interactions}, journal = {Chembiochem}, volume = {7}, year = {2006}, note = {Chembiochem003SDTimes Cited:39Cited References Count:25}, month = {Jan}, pages = {65-73}, abstract = {

Hyperpolarized Xe-129 NMR spectroscopy can detect the presence of specific low-concentration biomolecular analytes by means of a xenon biosensor that consists of a water-soluble, targeted cryptophane-A cage that encapsulates the xenon. In this work, we use the prototypical biotinylated xenon biosensor to determine the relationship between the molecular composition of the xenon biosensor and the characteristics of protein-bound resonances. The effects of diastereomer overlap, dipole-dipole coupling, chemical-shift anisotropy, xenon exchange, and biosensor conformotional exchange on the protein-bound biosensor signal were assessed. It was found that an optimal protein-bound biosensor signal can be obtained by minimizing the number of biosensor diastereomers and using a flexible linker of appropriate length. Both the line width and sensitivity of chemical shift to protein binding of the xenon biosensor were found to be inversely proportional to linker length.

}, keywords = {complexes}, isbn = {1439-4227}, doi = {Doi 10.1002/Cbic.200500327}, url = {://WOS:000234701000012}, author = {Lowery, T. J. and Garcia, S. and Chavez, L. and Ruiz, E. J. and Wu, T. and Brotin, T. and Dutasta, J. P. and King, D. S. and Schultz, P. G. and Pines, A. and Wemmer, D. E.} } @article {313, title = {Distinguishing multiple chemotaxis Y protein conformations with laser-polarized Xe-129 NMR}, journal = {Protein Science}, volume = {14}, year = {2005}, note = {Protein Sci907SSTimes Cited:23Cited References Count:27}, month = {Apr}, pages = {848-855}, abstract = {

The chemical shift of the Xe-129 NMR signal has been shown to be extremely sensitive to the local environment around the atom and has been used to follow processes such as ligand binding by bacterial periplasmic binding proteins. Here we show that the Xe-129 shift can sense more subtle changes: magnesium binding, BeF3- activation, and peptide binding by the Escherichia coli chemotaxis Y protein. H-1-N-15 correlation spectroscopy and X-ray crystallography were used to identify two xenon-binding cavities in CheY that are primarily responsible for the shift changes. One site is near the active site, and the other is near the peptide binding site.

}, keywords = {cavity}, isbn = {0961-8368}, doi = {Doi 10.1110/Ps.041231005}, url = {://WOS:000227738900002}, author = {Lowery, T. J. and Doucleff, M. and Ruiz, E. J. and Rubin, S. M. and Pines, A. and Wemmer, D. E.} } @article {317, title = {NMR-based biosensing with optimized delivery of polarized Xe-129 to solutions}, journal = {Analytical Chemistry}, volume = {77}, year = {2005}, note = {Anal Chem942GLTimes Cited:30Cited References Count:37}, month = {Jul 1}, pages = {4008-4012}, abstract = {

Laser-enhanced (LE) Xe-129 nuclear magnetic resonance (NMR) is an exceptional tool for sensing extremely small physical and chemical changes; however, the difficult mechanics of bringing polarized xenon and samples of interest together have limited applications, particularly to biological molecules. Here we present a method for accomplishing solution Xe-129 biosensing based on flow (bubbling) of LE Xe-129 gas through a solution in situ in the NMR probe, with pauses for data acquisition. This overcomes fundamental limitations of conventional solution-state LE Xe-129 NMR, e.g., the difficulty in transferring hydrophobic xenon into aqueous environments, and the need to handle the sample to refresh LE Xe-129 after an observation pulse depletes polarization. With this new method, we gained a factor of \> 100 in sensitivity due to improved xenon transfer to the solution and the ability to signal average by renewing the polarized xenon. Polarized xenon in biosensors was detected at very low concentrations, \<= 250 nanomolar, while retaining all the usual information from NMR. This approach can be used to simultaneously detect multiple sensors with different chemical shifts and is also capable of detecting signals from opaque, heterogeneous samples, which is a unique advantage over optical methods. This general approach is adaptable for sensing minute quantities of xenon in heterogeneous in vitro samples, in miniaturized devices and should be applicable to certain in-vivo environments.

}, keywords = {blood}, isbn = {0003-2700}, doi = {Doi 10.1021/Ac0500479}, url = {://WOS:000230270800035}, author = {Han, S. I. and Garcia, S. and Lowery, T. J. and Ruiz, E. J. and Seeley, J. A. and Chavez, L. and King, D. S. and Wemmer, D. E. and Pines, A.} } @article {333, title = {Design of a conformation-sensitive xenon-binding cavity in the ribose-binding protein}, journal = {Angewandte Chemie-International Edition}, volume = {43}, year = {2004}, note = {Angew Chem Int Edit877MVTimes Cited:10Cited References Count:20}, pages = {6320-6322}, keywords = {probe}, isbn = {1433-7851}, doi = {Doi 10.1002/Anie.200460629}, url = {://WOS:000225575600015}, author = {Lowery, T. J. and Rubin, S. M. and Ruiz, E. J. and Pines, A. and Wemmer, D. E.} } @article {325, title = {Development of a functionalized xenon biosensor}, journal = {Journal of the American Chemical Society}, volume = {126}, year = {2004}, note = {J Am Chem Soc872UHTimes Cited:60Cited References Count:76}, month = {Nov 24}, pages = {15287-15294}, abstract = {

NMR-based biosensors that utilize laser-polarized xenon offer potential advantages beyond current sensing technologies. These advantages include the capacity to simultaneously detect multiple analytes, the applicability to in vivo spectroscopy and imaging, and the possibility of \"remote\" amplified detection. Here, we present a detailed NMR characterization of the binding of a biotin-derivatized caged-xenon sensor to avidin. Binding of \"functionalized\" xenon to avidin leads to a change in the chemical shift of the encapsulated xenon in addition to a broadening of the resonance, both of which serve as NMR markers of ligand-target interaction. A control experiment in which the biotin-binding site of avidin was blocked with native biotin showed no such spectral changes, confirming that only specific binding, rather than nonspecific contact, between avidin and functionalized xenon leads to the effects on the xenon NMR spectrum. The exchange rate of xenon (between solution and cage) and the xenon spin-lattice relaxation rate were not changed significantly upon binding. We describe two methods for enhancing the signal from functionalized xenon by exploiting the laser-polarized xenon magnetization reservoir. We also show that the xenon chemical shifts are distinct for xenon encapsulated in different diastereomeric cage molecules. This demonstrates the potential for tuning the encapsulated xenon chemical shift, which is a key requirement for being able to multiplex the biosensor.

}, keywords = {drug discovery}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja0483037}, url = {://WOS:000225233600051}, author = {Spence, M. M. and Ruiz, E. J. and Rubin, S. M. and Lowery, T. J. and Winssinger, N. and Schultz, P. G. and Wemmer, D. E. and Pines, A.} } @article {354, title = {Detection and characterization of xenon-binding sites in proteins by Xe-129 NMR spectroscopy}, journal = {Journal of Molecular Biology}, volume = {322}, year = {2002}, note = {J Mol Biol597PTTimes Cited:53Cited References Count:54}, month = {Sep 13}, pages = {425-440}, abstract = {

Xenon-binding sites in proteins have led to a number of applications of xenon in biochemical and structural studies. Here we further develop the utility of Xe-129 NMR in characterizing specific xenon-protein interactions. The sensitivity of the Xe-129 chemical shift to its local environment and the intense signals attainable by optical pumping make xenon a useful NMR reporter of its own interactions with proteins. A method for detecting specific xenon-binding interactions by analysis of Xe-129 chemical shift data is illustrated using the maltose binding protein (MBP) from Escherichia coli as an example. The crystal structure of MBP in the presence of 8 atm of xenon confirms the binding site determined from NMR data. Changes in the structure of the xenon-binding cavity upon the binding of maltose by the protein can account for the sensitivity of the Xe-129 chemical shift to MBP conformation. Xe-129 NMR data for xenon in solution with a number of cavity containing phage T4 lysozyme mutants show that xenon can report on cavity structure. In particular, a correlation exists between cavity size and the binding-induced Xe-129 chemical shift. Further applications of Xe-129 NMR to biochemical assays, including the screening of proteins for xenon binding for crystallography are considered. (C) 2002 Elsevier Science Ltd. All rights reserved

}, keywords = {nonpolar cavity}, isbn = {0022-2836}, doi = {Doi 10.1016/S0022-2836(02)00739-8}, url = {://WOS:000178230500014}, author = {Rubin, S. M. and Lee, S. Y. and Ruiz, E. J. and Pines, A. and Wemmer, D. E.} } @article {367, title = {Detection of a conformational change in maltose binding protein by Xe-129 NMR spectroscopy}, journal = {Journal of the American Chemical Society}, volume = {123}, year = {2001}, note = {J Am Chem Soc467XNTimes Cited:28Cited References Count:28}, month = {Sep 5}, pages = {8616-8617}, keywords = {blood}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja0110325}, url = {://WOS:000170729200029}, author = {Rubin, S. M. and Spence, M. M. and Dimitrov, I. E. and Ruiz, E. J. and Pines, A. and Wemmer, D. E.} } @article {364, title = {Functionalized xenon as a biosensor}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {98}, year = {2001}, note = {P Natl Acad Sci USA472CZTimes Cited:112Cited References Count:29}, month = {Sep 11}, pages = {10654-10657}, abstract = {

The detection of biological molecules and their interactions is a significant component of modern biomedical research. In current biosensor technologies, simultaneous detection is limited to a small number of analytes by the spectral overlap of their signals. We have developed an NMR-based xenon biosensor that capitalizes on the enhanced signal-to-noise, spectral simplicity, and chemical-shift sensitivity of laser-polarized xenon to detect specific biomolecules at the level of tens of nanomoles. We present results using xenon \"functionalized\" by a biotin-modified supramolecular cage to detect biotin-avidin binding. This biosensor methodology can be extended to a multiplexing assay for multiple analytes.

}, keywords = {mri}, isbn = {0027-8424}, doi = {Doi 10.1073/Pnas.191368398}, url = {://WOS:000170966800030}, author = {Spence, M. M. and Rubin, S. M. and Dimitrov, I. E. and Ruiz, E. J. and Wemmer, D. E. and Pines, A. and Yao, S. Q. and Tian, F. and Schultz, P. G.} }