We report a novel diagonal suppressed two-dimensional total correlation experiment in solution state and demonstrate its performance in 1H and 2H NMR. In DIagonal Suppressed spin echo TOtal Correlation SpectroscopY (DISTOCSY), diagonal peaks which occur around F1 = 0 in spin echo mode are removed by conversion to unobservable multiple quantum or longitudinal terms in each scan of a two scan procedure, on application of an appropriately phased 90° pulse at the time of the echo maximum. The limitation of this approach to short FID acquisition times is discussed, and an alternative two-scan version of DISTOCSY for high resolution situations is presented. © 2015 Elsevier B.V. All rights reserved.

N Chandrakumar

Department Of Chemistry

physical chemistry

ACQUISITION TIME

DIAGONAL PEAKS

High resolution

SPIN ECHO

total correlation spectroscopy

UNOBSERVABLE

Spin polarization

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IIT Madras

Chemical Physics Letters

Two-dimensional nuclear magnetic resonance (2D NMR) correlation spectra help visualize inter- or intra-molecular spin connectivity through space or through bonds. This is accomplished by magnetization transfer between interacting (connected) spins located at different sites in molecules. In homonuclear 2D experiments, cross peaks which demonstrate spin connectivity and result from magnetization transfer between sites are unfortunately invariably accompanied by other peaks that result from magnetization that has not undergone any transfer, viz., diagonal peaks. The latter can often mask close-lying cross peaks. We report here the general principles that constitute a design strategy for diagonal suppression, relying on echo formation. Next, a novel experiment that effects diagonal suppression in the high-resolution mode is demonstrated. Pure phase capability is also introduced. Examples from both 2D exchange and high-resolution 2D correlation spectroscopy are included, and the proposed method is compared with other established as well as recent attempts to accomplish diagonal suppression. © 2014 American Chemical Society.

Journal of Physical Chemistry A

Two-dimensional nuclear magnetic resonance: Exploiting spin echoes to maximize information content by suppression of diagonal peaks in homonuclear experiments

Two dimensional homonuclear 1H correlation spectroscopy is of considerable interest for volume localized spectral studies, both in vivo and in vitro, of biological as well as material objects. The information principally sought from correlation spectra resides in the cross-peaks, which are often masked however by the presence of diagonal peaks in COSY, or 'pseudo-diagonal' peaks at F1 = 0 in SECSY. It has therefore been a concern to suppress these diagonal or 'pseudo-diagonal' peaks, in order to ensure that cross-peak information is fully discernible. We present here a report of our work on volume localized DIagonal Suppressed Spin Echo Correlation specTroscopy (LDISSECT) and demonstrate its performance in comparison to the standard volume localized SECSY experiment, employing brain metabolite phantoms in a gel. The sequence works in the inhomogeneous, multi-component environment by exploiting the short acquisition time to suppress undesired information by employing an additional rf pulse. A brief description of the pulse sequence, its theory, and simulations are also included, besides experimental benchmarking on two brain metabolite phantoms in gel phase. © 2013 Elsevier Inc. All rights reserved.

Journal of Magnetic Resonance

Volume localized spin echo correlation spectroscopy with suppression of 'diagonal' peaks

Overhauser-DNP-enhanced homonuclear 2D 19F correlation spectroscopy with diagonal suppression is presented for small molecules in the solution state at moderate fields. Multi-frequency, multi-radical studies demonstrate that these relatively low-field experiments may be operated with sensitivity rivalling that of standard 200-1000MHz NMR spectroscopy. Structural information is accessible without a sensitivity penalty, and diagonal suppressed 2D NMR correlations emerge despite the general lack of multiplet resolution in the 1D ODNP spectra. This powerful general approach avoids the rather stiff excitation, detection, and other special requirements of high-field 19FNMR spectroscopy. © 2014 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

Angewandte Chemie - International Edition

Chemical-shift-resolved 19FNMR spectroscopy between 13.5 and 135MHz: Overhauser-DNP-enhanced diagonal suppressed correlation spectroscopy

A novel ultrafast 2D NMR experiment is introduced for homonuclear correlation spectroscopy in solution state, with diagonal peak suppression in each scan of a two scan procedure. This experiment permits clear visualization of cross peaks between spins whose chemical shifts are very close, which could otherwise be masked by diagonal peaks. The present report describes the principles of its design and illustrates actual performance. © 2014 AIP Publishing LLC.

Fulltext

Journal of Chemical Physics

Communication: Ultrafast homonuclear correlation spectroscopy with diagonal suppression

The behavior of spin- 1 2 AX3 and A2X2 systems evolving under cross-polarization (CP) and isotropic mixing (IM) is analyzed in detail by computing the time development of the density operator by commutator algebra. The two mixing processes are compared in these cases with respect to their coherence-transfer frequencies, efficiency, and the resulting multiplet patterns. The effect of two types of purge on the density operator is evaluated for the heteronuclear situation. Spin- 1 2 AXN systems (N = 1, 2, ..., 6) evolving under isotropic mixing are also analyzed employing zero-quantum-frame techniques. Several general properties of isotropic mixing are derived which contrast with the corresponding cross-polarization results. Explicit expressions are given for the X-coupled and gX-decoupled A signal as a function of the isotropic mixing period. The effect of two different purge procedures is evaluated for the heteronuclear case, and general conclusions are drawn about the intensity and time development of the multiplet components in CP and IM. The IM results, except for the discussion of purging, are directly applicable to experiments involving homonuclear spin-locking as well. © 1986.

Journal	Data powered by TypesetChemical Physics Letters
Publisher	Data powered by TypesetElsevier
ISSN	00092614
Open Access	No