Functional and shunt states of bacteriorhodopsin resolved by 250 GHz dynamic nuclear polarization–enhanced solid-state NMR
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No Canadian affiliation. An affiliation-only frame — the usual design — would never have seen this work. It is one of the works that make the case for inverting the frame.
Machine scores (provisional)
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
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- Teacher spread
- 0.276 · how far apart the two teachers sit on this one work
- Validation status
score_only:v0-immature-baseline· verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it
Abstract
Observation and structural studies of reaction intermediates of proteins are challenging because of the mixtures of states usually present at low concentrations. Here, we use a 250 GHz gyrotron (cyclotron resonance maser) and cryogenic temperatures to perform high-frequency dynamic nuclear polarization (DNP) NMR experiments that enhance sensitivity in magic-angle spinning NMR spectra of cryo-trapped photocycle intermediates of bacteriorhodopsin (bR) by a factor of approximately 90. Multidimensional spectroscopy of U-(13)C,(15)N-labeled samples resolved coexisting states and allowed chemical shift assignments in the retinylidene chromophore for several intermediates not observed previously. The correlation spectra reveal unexpected heterogeneity in dark-adapted bR, distortion in the K state, and, most importantly, 4 discrete L substates. Thermal relaxation of the mixture of L's showed that 3 of these substates revert to bR(568) and that only the 1 substate with both the strongest counterion and a fully relaxed 13-cis bond is functional. These definitive observations of functional and shunt states in the bR photocycle provide a preview of the mechanistic insights that will be accessible in membrane proteins via sensitivity-enhanced DNP NMR. These observations would have not been possible absent the signal enhancement available from DNP.
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The record
- Venue
- Proceedings of the National Academy of Sciences
- Topic
- Advanced NMR Techniques and Applications
- Field
- Chemistry
- Canadian institutions
- —
- Funders
- National Institute of Biomedical Imaging and BioengineeringNatural Sciences and Engineering Research Council of CanadaNational Institutes of Health
- Keywords
- BacteriorhodopsinMagic angle spinningNuclear magnetic resonance spectroscopyChemistrySolid-state nuclear magnetic resonanceSpectroscopyNuclear magnetic resonanceChromophoreRelaxation (psychology)Spectral lineNMR spectra databaseHalobacteriaceaeHyperpolarization (physics)Polarization (electrochemistry)Analytical Chemistry (journal)PhotochemistryPhysical chemistryMembraneStereochemistryPhysicsHalobacterium salinarum
- Has abstract in OpenAlex
- yes