A spectral window in protein NMR revealing cross-relaxation between amide protons

Geoffrey Bodenhausen
1998
Journal paper

The principle of quenching undesirable indirect external trouble in nuclear Overhauser effect spectroscopy (QUIET-NOESY) relies on a doubly selective inversion of the longitudinal magnetization components of a source spin A and a target spin X to measure the cross-relaxation rate (Overhauser effect) between A and X without significant perturbation by spin diffusion. In 15N-enriched proteins, this can be achieved by using a bilinear rotation decoupling (BIRD) sequence for the selective inversion of amide protons that have a scalar coupling to nitrogen-15. The procedure can be improved by using editing techniques to simplify the resulting NOESY spectra. [on SciFinder (R)]

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Geoffrey Bodenhausen
1998
Journal paper

Abstract

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https://infoscience.epfl.ch/record/80365?ln=en

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Related publications

Coherence transfer in nuclear magnetic resonance by selective homonuclear Hartmann-Hahn correlation spectroscopy

Geoffrey Bodenhausen, Robert Konrat

New NMR techniques are described for transferring transverse magnetization between scalar-coupled nuclei in the rotating frame. The methods involve simultaneous spin-locking of two selected spins A and X, using cosinusoidal modulation of the radio frequency (rf) carrier. If transverse magnetization of spin A is excited selectively before spin-locking, for example with a self-refocusing 270 Deg Gaussian pulse, in-phase magnetization will be transferred from spin A to spin X, and in-phase multiplets are obtained in both one- and two-dimensional spectra. The method allows one to verify whether two particular spins are connected by a scalar coupling. Examples are shown for peptides and basic pancreatic trypsin inhibitor (BPTI). The fine structure of the multiplets yields information on couplings to further spins. In contrast to nonselective spin-lock expts., the magnetization cannot diffuse to a manifold of coupling partners. If relayed coherence transfer is to be achieved deliberately, several spins may be locked simultaneously by imposing an addnl. modulation on the rf carrier. [on SciFinder (R)]

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Effects of homonuclear scalar couplings during multiple refocusing sequences in nuclear magnetic resonance

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Multiple refocusing cycles can be used to extract transverse relaxation rates, R2, while homonuclear scalar couplings do not interfere. In this work, I have demonstrated the usefulness of a hybrid sequence, which is a compromise between single and multiple refocusing sequences, in order to investigate homonuclear scalar coupled spin systems, and to find a regime where the decays used to extract transverse relaxation rates are not modulated by cosine functions due to J-couplings. It was possible to measure the transverse relaxation rates of carbon-13 in doubly-enriched glycine and compare them with those of carbon-13 in singly-enriched glycine samples, which were in good agreement, and confirmed the feasibility of extracting R2 rates in coupled spin systems. I also investigated spin systems with more than one J-coupling interaction, and showed by experiments and numerical simulations that the increased complexity of the system reduces the possibilities of extracting unmodulated decays.

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A heteronuclear double-resonance (HDR) method based on MLEV-32 or WALTZ-32 pulse sequences has been designed for the investigation of relaxation of heteronuclear multiple-quantum (MQ) coherences. The theoretical analysis of this technique uses average Hamiltonian theory (AHT) to treat the effects of coherent evolution associated with scalar couplings, offsets, and inhomogeneous radiofrequency (rf) fields during the pulse sequence. Under most conditions, the dynamics of the MQ coherences during the HDR sequence is not affected by rf inhomogeneities and scalar couplings for offsets as large as the nutation frequency. The predictions drawn from AHT are supported by numerical simulations and experiments.

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