Polarization-Enhanced NMR Spectroscopy of Biomolecules in Frozen Solution

Hall, Dennis A.; Maus, Douglas; Gerfen, Gary J.; Inati, Souheil; Becerra, Lino; Dahlquist, Frederick W.; Griffin, Robert G.

doi:10.1126/science.276.5314.930

Cited by 507 publications

(524 citation statements)

References 18 publications

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“…Typical pulse sequences for DNP enhanced MAS experiments are described in several papers [29,43,49,50] and the sequence used to acquire the multidimensional spectra presented here is illustrated in Figure 3.…”

Section: Dnp Experiments On the Membrane Protein Bacteriorhodopsinmentioning

confidence: 99%

“…Traditional approaches, based on the solid effect and thermal mixing, yield enhancements that are an order of magnitude smaller [38] or require high concentrations of polarizing agents that lead to significant electron-nuclear dipolar broadening [42]. In addition, the 140 GHz system permitted us to develop and refine a number of experimental techniques, for example MAS at 90 K and lower temperatures [42,43]. Finally, over the last few years, research with the 140 GHz system led to increases in DNP enhancements in MAS experiments from ~10 to ~300 [28,35].…”

Section: Introductionmentioning

confidence: 99%

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250GHz CW gyrotron oscillator for dynamic nuclear polarization in biological solid state NMR

Bajaj

Hornstein

Kreischer

et al. 2007

Journal of Magnetic Resonance

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162

130

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In this paper, we describe a 250 GHz gyrotron oscillator, a critical component of an integrated system for magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments at 9T, corresponding to 380 MHz 1 H frequency. The 250 GHz gyrotron is the first gyro-device designed with the goal of seamless integration with an NMR spectrometer for routine DNP-enhanced NMR spectroscopy and has operated under computer control for periods of up to 21 days with a 100% duty cycle. Following a brief historical review of the field, we present studies of the membrane protein bacteriorhodopsin (bR) using DNP-enhanced multidimensional NMR. These results include assignment of active site resonances in [U-13 C, 15 N]-bR and demonstrate the utility of DNP for studies of membrane proteins. Next, we review the theory of gyro-devices from quantum mechanical and classical viewpoints and discuss the unique considerations that apply to gyrotron oscillators designed for DNP experiments. We then characterize the operation of the 250 GHz gyrotron in detail, including its long-term stability and controllability. We have measured the spectral purity of the gyrotron emission using both homodyne and heterodyne techniques. Radiation intensity patterns from the corrugated waveguide that delivers power to the NMR probe were measured using two new techniques to confirm pure mode content: a thermometric approach based on the temperaturedependent color of liquid crystalline media applied to a substrate and imaging with a pyroelectric camera. We next present a detailed study of the mode excitation characteristics of the gyrotron. Exploration of the operating characteristics of several fundamental modes reveals broadband continuous frequency tuning of up to 1.8 GHz as a function of the magnetic field alone, a feature that may be exploited in future tunable gyrotron designs. Oscillation of the 250 GHz gyrotron at the second harmonic of cyclotron resonance begins at extremely low beam currents (as low 12 mA) at frequencies between 320-365 GHz, suggesting an efficient route for the generation of even higher frequency radiation. The low starting currents were attributed to an elevated cavity Q, which is confirmed by cavity thermal load measurements. We conclude with an appendix containing a detailed description of the control system that safely automates all aspects of the gyrotron operation.

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Section: Dnp Experiments On the Membrane Protein Bacteriorhodopsinmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

250GHz CW gyrotron oscillator for dynamic nuclear polarization in biological solid state NMR

Bajaj

Hornstein

Kreischer

et al. 2007

Journal of Magnetic Resonance

Self Cite

162

130

View full text Add to dashboard Cite

show abstract

“…As a means to increase the sensitivity of these experiments, we have previously employed dynamic nuclear polarization (DNP) to enhance NMR signals in both static and rotating solids at 5T [16][17][18][19]. DNP involves the irradiation of a coupled electron-nuclear spin system in the neighborhood of the electron Larmor frequency.…”

Section: Introductionmentioning

confidence: 99%

Dynamic nuclear polarization at 9T using a novel 250GHz gyrotron microwave source

Bajaj¹,

Farrar²,

Hornstein³

et al. 2003

Journal of Magnetic Resonance

218

191

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In this communication, we report enhancements of nuclear spin polarization by dynamic nuclear polarization (DNP) in static and spinning solids at a magnetic field strength of 9T (250 GHz for g = 2 electrons, 380 MHz for 1 H). In these experiments, 1 H enhancements of up to 170 ± 50 have been observed in 1-13 C-glycine dispersed in a 60:40 glycerol/water matrix at temperatures of 20 K; in addition, we have observed significant enhancements in 15 N spectra of unoriented pf1-bacteriophage. Finally, enhancements of ~17 have been obtained in two-dimensional 13 C-13 C chemical shift correlation spectra of the amino acid U-13 C, 15 N-proline during magic angle spinning (MAS), demonstrating the stability of the DNP experiment for sustained acquisition and for quantitative experiments incorporating dipolar recoupling. In all cases, we have exploited the thermal mixing DNP mechanism with the nitroxide radical 4-amino-TEMPO as the paramagnetic dopant. These are the highest frequency DNP experiments performed to date and indicate that significant signal enhancements can be realized using the thermal mixing mechanism even at elevated magnetic fields. In large measure, this is due to the high microwave power output of the 250 GHz gyrotron oscillator used in these experiments.

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“…Amplifying the available magnetization has been the focus of many studies, leading to various hyperpolarization (hp) techniques such as hp noble gases (1,2), para-hydrogen induced polarization transfer (3,4), or dynamic nuclear polarization (5). Exploiting chemical exchange of nuclei of a hyperpolarized reservoir in combination with a mechanism of gated transfer onto the molecule of interest would provide optimized, controlled 'utilization' of the hyperpolarization (Fig 1a), hence avoiding polarization losses during transfer reactions.…”

mentioning

confidence: 99%

Temperature‐Controlled Molecular Depolarization Gates in Nuclear Magnetic Resonance

et al. 2008

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Polarization-Enhanced NMR Spectroscopy of Biomolecules in Frozen Solution

Cited by 507 publications

References 18 publications

250GHz CW gyrotron oscillator for dynamic nuclear polarization in biological solid state NMR

250GHz CW gyrotron oscillator for dynamic nuclear polarization in biological solid state NMR

Dynamic nuclear polarization at 9T using a novel 250GHz gyrotron microwave source

Temperature‐Controlled Molecular Depolarization Gates in Nuclear Magnetic Resonance

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