Proton NMR Relaxation Effects. Cross-Relaxation Processes in Pure Liquids

Brooks, Al; Cutnell, John D.; Stejskal, E. O.; Weiss, V. W.

doi:10.1063/1.1670280

Cited by 35 publications

(12 citation statements)

References 22 publications

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“…For a dipolar coupled two-spin (I -S) system, Solomon derived simultaneous differential equations, 16 which was further extended to a system with a dilute S spin in abundant I spins having a common spin temperature. 17 Under the steady-state condition with 1 H saturation, the NOE factor can formally be written as…”

Section: Theorymentioning

confidence: 99%

C 13 nuclear Overhauser polarization nuclear magnetic resonance in rotating solids: Replacement of cross polarization in uniformly C13 labeled molecules with methyl groups

Takegoshi¹,

Terao²

2002

The Journal of Chemical Physics

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A new 13 C polarization technique in solids is presented on the basis of a recently proposed 13 C-13 C recoupling sequence ͓ 13 C-1 H dipolar-assisted rotational resonance ͑DARR͒, K. Takegoshi, S. Nakamura, and T. Terao, Chem. Phys. Lett. 344, 631 ͑2001͔͒ operative under fast magic angle spinning ͑MAS͒, in which a rf field is applied to 1 H with a rotary resonance condition but none to 13 C. The 1 H irradiation in DARR saturates 1 H signals, leading to the 13 C signal enhancement due to the nuclear Overhauser effect for fast rotating methyl groups, if any. If we use a uniformly 13 C labeled sample, 13 C-13 C polarization transfer enhanced by DARR successively distributes the enhanced methyl carbon polarization to the other 13 C spins, leading to uniform enhancement for all 13 C spins even under very fast MAS. In uniformly 13 C labeled rotating samples, the enhancement factor in cross polarization ͑CP͒ is about 2.4, while in the present nuclear Overhauser polarization ͑NOP͒, it is 3.0 in the fast rotation limit of the methyl groups. While the CP enhancement becomes smaller for molecules with short T 1 of 1 H or 13 C, NOP would work well for such mobile molecules, and also NOP enables us to acquire a signal with a short repetition time even if 1 H T 1 is long. Further, NOP has the advantage of quantitativeness, and is very easy to carry out, being insensitive to the adjustment of rf field intensity and requiring only very low rf power. These features are demonstrated for uniformly 13 C, 15 N-labeled L-threonine and uniformly 13 C, 15 N-labeled glycylisoleucine. NOP-MAS is also applied for a naturally abundant 13 C sample.

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Section: Theorymentioning

confidence: 99%

C 13 nuclear Overhauser polarization nuclear magnetic resonance in rotating solids: Replacement of cross polarization in uniformly C13 labeled molecules with methyl groups

Takegoshi¹,

Terao²

2002

The Journal of Chemical Physics

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“…33 The three compounds studied here provide other examples over a wider range of temperatures than that employed by Brooks, Cutnell, Stejskal, and Weiss. 33 The three compounds studied here provide other examples over a wider range of temperatures than that employed by Brooks, Cutnell, Stejskal, and Weiss.…”

Section: Appendixmentioning

confidence: 94%

Nuclear Spin-Lattice and Viscoelastic Relaxation in Selected Hydrocarbon Liquids

Cutnell

Stejskal

1972

The Journal of Chemical Physics

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Spin-lattice relaxation rates of 5,5,11,1l-tetramethylhexadecane, squalane, and squalene have been measured as a function of temperature via pulsed NMR techniques. These relaxation rates are discussed in terms of molecular models which yield nonexponential correlation functions. The particular models employed are based on cooperative relaxation mechanisms which have been found useful in viscoelastic and dielectric relaxation studies. It is found that such mechanisms are also pertinent in the nuclear spin relaxation behavior of these compounds. The distribution of correlation times useful in describing shear relaxation data is also found to be useful in describing spin relaxation data.

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“…Within the experiniental error the ratios T1,/T,, are close to the theoretical values expected frorn eq. [14].…”

Section: Discussionmentioning

confidence: 99%

“…One of the most difficult problems in the saturation-recovery method applied to systems with several nonequivalent spins is the general possibility that the recovery curves are represented by the sum of a number of exponential terms with different coefficients, even in the absence of spin-spin coupling (8, 13,14). Therefore it is necessary to divide these curves into separate exponential terms or to prove by special experiments and calculations that the experimental curves depend mostly on only one exponential term, i.e., the coefficients of other terms are negligible.…”

Section: Introductionmentioning

confidence: 99%

The proton relaxation and Overhauser effect in the nuclear magnetic resonance spectra of some amides

Brownstein¹,

Bystrov²

1970

Can. J. Chem.

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The relaxation behavior of some amides was investigated in their high resolution spectra by the direct saturation-recovery and Overhauser effect methods. The recovery curves and steady-state Overhauser effects were obtained for solutions of dimethylformamide with double-and triple-resonance irradiations. The results were analyzed for 3-and 4-spin systems and the values of relaxation parameters were calculated. It was shown that for dimethylformamide the one-exponential recovery curve approximation gives the TI values with a precision better than experimental error (f 2%). The observed difference in relaxation times for methyl group protons was explained by different correlation times and more restricted rotation of 1 of the groups. The correlation times for dipole-dipole interactions of methyl groups with the forrnyl proton were also evaluated with some reasonable assumptions.The change of the relaxation rate of N-methyl protons in C6H6 and C6D6 solutions was explained by formation of the collision complex with amide molecules and specific intermolecular dipole-dipole proton interaction. This effect could be useful for determination of the cis-and trans-conformations in N-methyl substituted amides and peptides as an absolute method because it does not require measurements on both isomers.

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Proton NMR Relaxation Effects. Cross-Relaxation Processes in Pure Liquids

Cited by 35 publications

References 22 publications

C 13 nuclear Overhauser polarization nuclear magnetic resonance in rotating solids: Replacement of cross polarization in uniformly C13 labeled molecules with methyl groups

C 13 nuclear Overhauser polarization nuclear magnetic resonance in rotating solids: Replacement of cross polarization in uniformly C13 labeled molecules with methyl groups

Nuclear Spin-Lattice and Viscoelastic Relaxation in Selected Hydrocarbon Liquids

The proton relaxation and Overhauser effect in the nuclear magnetic resonance spectra of some amides

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