A convenient method for the measurements of transverse relaxation rates in homonuclear scalar coupled spin systems

Laboratoire Chimie Provence, Spectrométries Appliquées à la Chimie Structurale, UMR 6264, Université Aix-Marseille I-CNRS, 13397 Marseille, France.
Chemical Communications (Impact Factor: 6.83). 08/2011; 47(32):9209-11. DOI: 10.1039/c1cc13042k
Source: PubMed


A new solution-state NMR method is proposed to determine apparent transverse NMR relaxation rates in both weakly and strongly scalar coupled two-spin systems.

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    • "With PFCT echoes and MQF sequences, complete decoupling is limited to AX-systems and the decays reflect linear combinations of transverse relaxation rates of various coherences that depend on s. Furthermore, the MQF sequence needs an 8-step phase cycle [4]. Therefore, the use of these techniques to measure transverse relaxation in homonuclear coupled systems does not appear to be practical. "
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    ABSTRACT: Homogeneous line-widths that arise from transverse relaxation tend to be masked by B0 field inhomogeneity and by multiplets due to homonuclear J-couplings. Besides well-known spin-locking sequences that lead to signals that decay with a rate R1ρ without any modulations, alternative experiments allow one to determine the transverse relaxation rates R2 in systems with scalar-coupled spins. We evaluate three recent strategies by experiment and simulation: (i) moderate-amplitude SITCOM-CPMG sequences (Dittmer and Bodenhausen, 2006 [2]), (ii) multiple-quantum filtered (MQF) sequences (Barrère et al., 2011 [4]) and (iii) PROJECT sequences (Aguilar et al., 2012 [5]). Experiments where the J-evolution is suppressed by spin-locking measure the pure relaxation rate R2(Ix) of an in-phase component. Experiments based on J-refocusing yield a mixture of in-phase rates R2(Ix) and antiphase rates R2(2IySz), where the latter are usually faster than the former. Moderate-amplitude SITCOM-CPMG and PROJECT methods can be applied to systems with many coupled spins, but applications of MQF sequences are limited to two-spin systems since modulations in larger systems can only partly be suppressed.
    Full-text · Article · Oct 2013 · Journal of Magnetic Resonance
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    • "techniques have been developed such as resonance-specific selective irradiation [2] [3] and a variety of 1D [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] and 2D approaches [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35]. "
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    ABSTRACT: Homonuclear 1H-1H J-modulation leads to J-multiplets in F1 dimension of 2D 1H-13C HMQC spectra. This hampers unambiguous signal assignment for overcrowded 13C spectra. Broadband homonuclear decoupling has been achieved in the indirect t1 evolution period by incorporating blocks of perfect echo. This method enhances resolution and sensitivity of 2D 1H-13C HMQC spectra. The results on Cyclosporine demonstrate that the method is very efficient for -13CH2 groups, though partial sensitivity and resolution enhancements have also been observed for -13CH and -13CH3 groups. Interpretation of the result based on product operator formalism is also given.
    Full-text · Article · Jun 2013 · Journal of Magnetic Resonance
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    ABSTRACT: The spin echo is the single most important building block in modern NMR spectroscopy, but echo modulation by scalar couplings J can severely complicate its use. We show for the first time that a general but unacknowledged solution to such complications already exists.
    Full-text · Article · Dec 2011 · Chemical Communications
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