heteronuclear single quantum coherence spectra

(D/E) 1D projection of the double-bond carbons (D) and glycerol carbons (E) summed over proton chemical shift ranges ppm and ppm, respectively. (C) 1D projection of the 13C ‘fingerprint’ region summed over proton chemical shifts between 0.0 and 3.5 ppm. (C-E) Summed 1D projections of the 2D HSQC spectra onto the carbon-13 axis. The inset shows the linolenic acid resonance B Ln with a twenty-fold increased vertical scale, together with a 1H- 13C resonance from correlation over multiple chemical bonds between the G position carbon-13 nucleus and the H position protons. Labels with an asterisk (*) indicate that the resonance is aliased along the carbon-13 dimension by an integer number of the carbon-13 spectral width. Besides the extended proton chemical shift axis, the 2D HSQC spectrum looks similar to those acquired in vitro (Fig. (B) 2D HSQC spectra acquired from the voxel shown in (A) in 19 min with TR variation (TR1/TR2/T 1 = 3000/500/1000 ms). (A) Anatomical MRI showing the placement of a 3 × 1 × 3 cm voxel. The line width increase and associated peak height reduction is most noticeable for the methyl resonance at 14.16 ppm (see Table 1 for a quantitative line width evaluation).ĢD HSQC on human adipose tissue in vivo. (D/E) Summed 1D projections of the 2D HSQC spectra in (B/C) onto the carbon-13 axis demonstrate minor line increases in (E). The chemical similarities of the various D groups make exact assignment difficult. Resonance D is composed of between 3 and 10 resonances. Note that resonances B and C are split due to unique B Ln and C L moieties and resonance J is split due to the different chemical environments caused by the α and β-glycerol groups. The indicated assignments correspond to the label defined in (A). (B/C) 2D HSQC data from a vegetable oil phantom acquired with (B) constant and (C) variable repetition times (TR1/TR2/T 1 = 3000/500/1000 ms). In those cases the labels become B Ln and C L. The carbon position labels A and D through K are generally applicable, whereas labels B and C are unique in the case of linolenic and linoleic acid, respectively. The α-glycerol positions are esterified to undefined R and R′ fatty acid chains. (A) Structure of a triglyceride in which the β-glycerol position is esterified to linoleic acid. 2D HSQC has a strong potential to become a default method in natural-abundance or (13) C-enriched studies of human metabolism in vivo.ĢD HSQC adipose tissue broadband decoupling carbon-13 triglycerides. The HSQC method is methodologically simple and robust and is flexible regarding trade-offs between temporal and spectral resolution. It has been demonstrated that high-quality 2D HSQC NMR spectra can be acquired from human adipose tissue at 7T. The high chemical specificity along the indirect (13) C dimension allowed the detection of 19 unique resonances from which the lipids could be characterized in terms of saturation and omega-6/omega-3 fatty acid ratio. Complete proton decoupling was achieved along the indirect (13) C dimension despite the absence of broadband proton-decoupling pulses. The low RF power deposition of the method allows TR variation along the indirect dimension which, in combination with controlled aliasing, leads to an acceleration of 11.8 relative to a standard 2D NMR acquisition.Īrtifact-free, high-quality and high-sensitivity 2D HSQC spectra were obtained for all subjects in 19 min from a small (9 mL) volume placed in the leg adipose tissue. Due to the 2D nature of the method, proton-decoupled (13) C MR spectra can be obtained without the use of high-powered decoupling pulses.Ī novel three-dimensional (3D) localized 2D HSQC method based on 3D STEAM localization is presented and implemented at 7T. Two-dimensional (2D) heteronuclear single quantum coherence (HSQC) MRS is a method that uses the high chemical specificity of (13) C MRS while retaining the high sensitivity of (1) H detection. While the use of higher magnetic fields can overcome the sensitivity limitations, high radiofrequency (RF) power deposition associated with proton-decoupling limits the achievable gain. Carbon-13 ((13) C) magnetic resonance spectroscopy (MRS) has an intrinsically low NMR sensitivity that often leads to large acquisition volumes or long scan times.

Heteronuclear single quantum coherence spectra