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Scalar Coupling (scalar + coupling)

Distribution by Scientific Domains

Chemistry	80%

Selected Abstracts

Indirect detection of the 183W and 57Fe nuclei using 119Sn-relayed 1H,X correlation spectroscopy

MAGNETIC RESONANCE IN CHEMISTRY, Issue 10 2010
T. Andrew Mobley
Abstract Recently reported triple-resonance Y-relayed 1H,X correlation experiments have been utilized to characterize 183W and 57Fe chemical shifts using 119Sn as the Y-relaying nucleus instead of the previously used 31P. Application of an adaptation of Gudat's original INEPT/HMQC sequence results in a significant enhancement of the signal-to-noise (S/N) ratio for two-dimensional 119Sn-relayed 1H,183W and 1H, 57Fe correlation spectra with efficient detection of the transition metal nucleus in tungsten and iron complexes lacking an observable direct scalar coupling between the transition metal and any hydrogen nuclei. Strengths and shortcomings of the novel sequence and the original sequences reported by Gudat are discussed in the context of 119Sn-relayed proton detection of very low frequency transition metal nuclei. Copyright © 2010 John Wiley & Sons, Ltd. [source]

1H,1H scalar coupling across two stacked aromatic rings: DFT calculations and experimental proof

MAGNETIC RESONANCE IN CHEMISTRY, Issue 3 2008
Giuseppe Bifulco
Abstract 1H,1H scalar coupling across two stacked (parallel and eclipsed) aromatic rings has been revealed through the 1D and 2D 1H NMR analysis of a [2,2]paracyclophane and rationalized by means of density functional theory (DFT) calculation of the J values. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Optimized detection of lactate at high fields using inner volume saturation

MAGNETIC RESONANCE IN MEDICINE, Issue 4 2006
Richard A.E. Edden
Abstract In localized proton MR spectroscopy (1H-MRS) in vivo, the detection of lactate (Lac) is affected by modulation of its resonances due to homonuclear scalar couplings (J). A simple and convenient way to distinguish Lac from lipids is to set the TE to 1/J so that the Lac signal is inverted while other resonances (such as lipid) remain in-phase. However, at high field strengths, such as 3 Tesla or above, the modulation of the Lac signal is complicated by chemical shift effects that cause modulation patterns to vary within different subregions of the localized volume. Under some conditions the Lac signal may even disappear completely. In this note we introduce the concept of inner volume saturation (IVS), which makes use of high bandwidth spatial pulses to remove the signal corresponding to the regions of the localized volume that contribute unwanted modulation patterns. The method is described theoretically and demonstrated experimentally at 3 Tesla in a phantom and a patient with acute stroke. The phantom measurements indicate that virtually 100% of the Lac signal can be recovered using this method. The method should be feasible at magnetic fields above 3 Tesla, and may also be applied to other coupled spin systems in which modulation effects are important. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [source]

Structure and hydration of the amylopectin trisaccharide building blocks,Synthesis, NMR, and molecular dynamics

BIOPOLYMERS, Issue 12 2008
Peter I. Hansen
Abstract To gain insight into the molecular details and hydration of amylopectin, the five constituting trisaccharides have been chemically synthesized as their methyl ,-glycosides. All five trisaccharides were subjected to 950 MHz NMR spectroscopy for complete assignment and nanosecond molecular dynamics trajectories were calculated to study the structure and dynamics of the trisaccharides in aqueous solution. Systematic analysis of the simulation data revealed several examples of bridging water molecules playing an important role in the stabilization of specific amylopectin conformations, which was also supported by the experimental NMR data such as interresidue NOE's and heteronuclear scalar couplings between nuclei from neighboring residues. Although ,-maltotriose, ,-iso-maltotriose, ,-panose and ,-isopanose are relatively well characterized structures, the study also includes one less characterized trisaccharide with the structure ,Glcp(1,4),Glcp(1,6),Glcp. This trisaccharide, tentatively labelled ,-forkose, is located at the branch point of amylopectin, forking the amylopectin into two strands that align into double-helical segments. The results show that the conformation of ,-forkose takes a natural bend form which fits well into the structure of the double-helical segment of amylopectin. As the only trisaccharide in this study the structure of ,-forkose is not significantly influenced by the hydration. In contrast, ,-isopanose takes a restricted, but rather extended form due to an exceptionally strong localized water density. The two homo-linkage oligomers, ,-maltotriose and ,-iso-maltotriose, showed to be the most extended and the most flexible trimers, respectively, providing regular structure for crystalline domains and maximum linker flexibility for amorphous domains. © 2008 Wiley Periodicals, Inc. Biopolymers 89: 1179,1193, 2008. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source]