In Situ Temperature Jump High-Frequency Dynamic Nuclear Polarization Experiments: Enhanced Sensitivity in Liquid-State NMR Spectroscopy
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- 作者：Chan-Gyu Joo ; Kan-Nian Hu ; Jeffrey A. Bryant ; and Robert G. Griffin
- 刊名：Journal of the American Chemical Society
- 出版年：2006
- 出版时间：July 26, 2006
- 年：2006
- 卷：128
- 期：29
- 页码：9428 - 9432
- 全文大小：104K
- 年卷期：v.128,no.29(July 26, 2006)
- ISSN：1520-5126
文摘
We describe an experiment, in situ temperature jump dynamic nuclear polarization (TJ-DNP),that is demonstrated to enhance sensitivity in liquid-state NMR experiments of low-
spins - 13C, 15N, etc.The approach consists of polarizing a sample at low temperature using high-frequency (140 GHz)microwaves and a biradical polarizing agent and then melting it rapidly with a pulse of 10.6 
m infraredradiation, followed by observation of the NMR signal in the presence of decoupling. In the absence ofpolarization losses due to relaxation, the enhancement should be 
= (Tobs/Twave), where is the observedenhancement, is the enhancement obtained at the temperature where the polarization process occurs,and Twave and Tobs are the polarization and observation temperatures, respectively. In a single experimentalcycle, we observe room-temperature enhancements, , of 13C signals in the range 120-400 when usinga 140 GHz gyrotron microwave source, Twave = 90 K, and Tobs = 300 K. In addition, we demonstrate thatthe experiment can be recycled to perform signal averaging that is customary in contemporary NMRspectroscopy. Presently, the experiment is applicable to samples that can be repeatedly frozen and thawed.TJ-DNP could also serve as the initial polarization step in experiments designed for rapid acquisition ofmultidimensional spectra.
spins - 13C, 15N, etc.The approach consists of polarizing a sample at low temperature using high-frequency (140 GHz)microwaves and a biradical polarizing agent and then melting it rapidly with a pulse of 10.6 m infraredradiation, followed by observation of the NMR signal in the presence of decoupling. In the absence ofpolarization losses due to relaxation, the enhancement should be = (Tobs/Twave), where is the observedenhancement, is the enhancement obtained at the temperature where the polarization process occurs,and Twave and Tobs are the polarization and observation temperatures, respectively. In a single experimentalcycle, we observe room-temperature enhancements, , of 13C signals in the range 120-400 when usinga 140 GHz gyrotron microwave source, Twave = 90 K, and Tobs = 300 K. In addition, we demonstrate thatthe experiment can be recycled to perform signal averaging that is customary in contemporary NMRspectroscopy. Presently, the experiment is applicable to samples that can be repeatedly frozen and thawed.TJ-DNP could also serve as the initial polarization step in experiments designed for rapid acquisition ofmultidimensional spectra.