A theoretical study of coherence transfer by isotropic mixing

Remerowski, M. Lyndsay; Glaser, Steffen J.; Drobny, Gary P.

doi:10.1080/00268978900102841

Cited by 29 publications

(11 citation statements)

References 18 publications

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“…In systems consisting of more than four coupled spins, the polarization of individual spins can become negative in isotropic mixing experiments (8,14). Hence, the exact correspondence cannot hold for more than four spins because the energy of a given pendulum cannot become less than zero.…”

Section: Discussionmentioning

confidence: 99%

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Spins swing like pendulums do: an exact classical model for TOCSY transfer in systems of three isotropically coupled spins 1/2

Marx

Glaser

2003

Journal of Magnetic Resonance

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Section: Discussionmentioning

confidence: 99%

“…Effective isotropic mixing conditions can also be created in heteronuclear spin systems by a number of well known pulse sequences (5,6,7). Simulating the transfer dynamics is important in practice because it enables spectroscopists to determine the optimal duration of isotropic mixing periods in NMR experiments (5,8,9).…”

Section: Introductionmentioning

confidence: 99%

Spins swing like pendulums do: an exact classical model for TOCSY transfer in systems of three isotropically coupled spins 1/2

Marx

Glaser

2003

Journal of Magnetic Resonance

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“…First, DIPSI minimizes non-scalar behavior. As discussed above, while the earlier sequences cancel linear spin operators across a wide bandwidth, during the mixing cycle, they also generate bilinear zero-, single-, and double quantum operators, leading to a decay in the amplitude of polarization transfer, as exhibited in dictratesofpolarization transfer insuchsystems, one usually resorts tonumerical solutions [125,126,127].…”

Section: Dipsi Mixingmentioning

confidence: 99%

Two-dimensional nuclear magnetic resonance studies of molecular structure in liquids and liquid crystals

Rucker¹

1991

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Magnetic couplings between protons, such as through-space dipole couplings, and scalar J-couplings depend sensitively on the structure of the molecule. Twodimensional nuclear magnetic resonance experiments provide a powerful tool for measuring these couplings, correlating them to specific pairs of protons within the molecule, and calculating the structure. This work discusses the development of NMR methods for examining two such classes of problems-determination of the secondary structure of flexible molecules in anisotropic solutions, and primary structure of large biomolecules in aqueous solutions. The anisotropic environment of liquid crystals prevents complete averaging of the proton-proton dipolar interaction, leading to intractably complex spectra. By a series of synthetic and spectroscopic steps, the residual dipole couplings for a series of alkanes (_hexane through _decane) are measured and assigned. These are used as experimental constraints for mean field models of the solute-solvent interaction. Such calculations yield values for the trans-gauche energ3r difference for the carboncarbon bonds, and give a time-averaged picture of the alkane's conformation and orientation withinthe liquid cystalline environment. Proton J-couplings in liquid-phase molecules providea directmeasure of the bond connectivities withinthe molecule, from which a structure can be derived. A new heteronuclear decoupling sequence, DIPSI-2,has been employed to transfer polarization betweencoupledspins. Thiswindowless radiofrequency pulsesequence generates much more efficient magnetization transfer than earlier sequences, yieldingtwo-dimensional spectra witLbetter cross-peak intensity and cleaner lineshapes. Two additional developments arealso discussed: the implementation ofiterative schemesto the generation ofmultiple-pulse echotechniques, and the measurement ofthe geometric component ofthe transition probability ina two-level system.By phase-shining the pulsesofa Cart-Purcell echo train, itsability to preserve both the amplitudeand phase of the magnetization isimproved dramatically. These echo sequencesfindapplication in imagingexperiments, where they areemployed forvolume selection, or improvementinsignal-to-noise. The secondtopicinvolves measuringthe effect ofa Hamiltonian's geometryon the transition probability of a two-level system duringa near-adiabatic radiofrequency sweep.This experiment verifies the existence ofa component of the probability that depends onlyon the shapeof thesweep profile, and not the rateofpassage.

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“…correlations if the longitudinal mixing period is used for However, for specific coupling topologies and chemical-shift constant-time evolution and if additional coherence transfer distributions, magnetization transfer is in general far from steps are added. For example, the application of directed being homogeneous (3)(4)(5)(6)(7)(8)(9). Through the use of TACSY TOCSY transfer to the ribose C1-C5 spins of uniformly experiments (tailored correlation spectroscopy) (9)(10)(11)(12), co-13 C-labeled RNA oligonucleotides yields selectively forherence transfer can often be restricted to a subset of spins ward-directed Ck, H(k / 1) correlations while Ck, Hk within an extended coupling network by exploiting the distri-autocorrelations and Ck, H(k 0 1) backward-directed corbution of chemical shifts and differences in the size of the relations are suppressed (cf.…”

Section: Introductionmentioning

confidence: 99%

Directed TOCSY, a Method for Selection of Directed Correlations by Optimal Combinations of Isotropic and Longitudinal Mixing

Glaser

Schwalbe

Marino

et al. 1996

Journal of Magnetic Resonance, Series B

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A theoretical study of coherence transfer by isotropic mixing

Cited by 29 publications

References 18 publications

Spins swing like pendulums do: an exact classical model for TOCSY transfer in systems of three isotropically coupled spins 1/2

Spins swing like pendulums do: an exact classical model for TOCSY transfer in systems of three isotropically coupled spins 1/2

Two-dimensional nuclear magnetic resonance studies of molecular structure in liquids and liquid crystals

Directed TOCSY, a Method for Selection of Directed Correlations by Optimal Combinations of Isotropic and Longitudinal Mixing

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