Evidence of nonspecific surface interactions between laser-polarized xenon and myoglobin in solution

TitleEvidence of nonspecific surface interactions between laser-polarized xenon and myoglobin in solution
Publication TypeJournal Article
Year of Publication2000
AuthorsRubin S.M, Spence M.M, Goodson B.M, Wemmer D.E, Pines A
JournalProceedings of the National Academy of Sciences of the United States of America
Volume97
Issue17
Pagination9472-9475
Date PublishedAug 15
ISBN Number0027-8424
Accession NumberWOS:000088840500026
Keywordsbinding
Abstract

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.

URL<Go to ISI>://WOS:000088840500026
DOI10.1073/Pnas.170278897
Short TitleEvidence of nonspecific surface interactions between laser-polarized xenon and myoglobin in solution
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