NMR resonance splitting of urea in stretched hydrogels: Proton exchange and 1 H/ 2 H isotopologues

Kuchel, Philip W.; Naumann, Christoph; Chapman, Bogdan E.; Shishmarev, Dmitry; Håkansson, Pär; Bacskay, George B.; Hush, Noel S.

doi:10.1016/j.jmr.2014.08.004

Cited by 7 publications

(4 citation statements)

References 34 publications

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“…To analyze the general structure of J -spectra of [ 15 N]-urea and [ 13 C, 15 N 2 ]-urea, first, numerical simulations are performed using J -coupling constants shown in Figure 1 . 20 , 21 Because one-bond 1 H– 15 N coupling in the −NH 2 group is the strongest interaction in this system, the main features in the J -spectra of both forms of urea are centered around (3/2)| 1 J NH | ≈ 133.65 Hz (marked by a dashed line in Figure 1 ), as expected for an XA 2 nuclear spin system corresponding to the transitions in the manifold with the total proton spin 1 (see, for example, refs ( 8 ) and ( 22 )). Hereafter, we refer to this group of peaks as high-frequency peaks.…”

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confidence: 99%

Zero-Field NMR of Urea: Spin-Topology Engineering by Chemical Exchange

Alcicek

Put

Barskiy

et al. 2021

J. Phys. Chem. Lett.

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Well-resolved and information-rich J -spectra are the foundation for chemical detection in zero-field NMR. However, even for relatively small molecules, spectra exhibit complexity, hindering the analysis. To address this problem, we investigate an example biomolecule with a complex J -coupling network—urea, a key metabolite in protein catabolism—and demonstrate ways of simplifying its zero-field spectra by modifying spin topology. This goal is achieved by controlling pH-dependent chemical exchange rates of 1 H nuclei and varying the composition of the D 2 O/H 2 O mixture used as a solvent. Specifically, we demonstrate that by increasing the proton exchange rate in the [ 13 C, 15 N 2 ]-urea solution, the spin system simplifies, manifesting through a single narrow spectral peak. Additionally, we show that the spectra of 1 H/D isotopologues of [ 15 N 2 ]-urea can be understood easily by analyzing isolated spin subsystems. This study paves the way for zero-field NMR detection of complex biomolecules, particularly in biofluids with a high concentration of water.

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confidence: 99%

Zero-Field NMR of Urea: Spin-Topology Engineering by Chemical Exchange

Alcicek

Put

Barskiy

et al. 2021

J. Phys. Chem. Lett.

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“…To analyse the general structure of J-spectra of [ 15 N]-urea and [ 13 C, 15 N 2 ]urea, first, numerical simulations are performed using J-coupling constants shown in Fig. 1 [21,22]. Since one-bond 1 H-15 N coupling in the -NH 2 group is the strongest interaction in this system, the main features in the J-spectra of both forms of urea are centered around (3/2)| 1 J NH | ≈ 133.65 Hz (marked by a dashed line in Fig.…”

Section: Resultsmentioning

confidence: 99%

Zero-field J-Spectroscopy of Urea: Spin-Topology Engineering by Chemical-Exchange

Alcicek

Put

Barskiy

et al. 2021

Preprint

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Well-resolved and information-rich J-spectra are the foundation for chemical analysis based on zero-field NMR. Yet, even in relatively small molecules, the spectra may gain complexity, hindering the analysis. To address this problem, we investigate an example biomolecule characterized with a complex J-coupling network -- urea, a key metabolite in protein catabolism -- and demonstrate ways of simplifying its zero-field spectra by modifying spin topology. This goal is achieved by controlling pH-dependent chemical-exchange rates of 1H nuclei and varying the composition of the D2O/H2O mixture used as a solvent. Specifically, we demonstrate that by increasing hydrogen chemical-exchange rate in [13C, 15N2]-urea solution, the molecule, being an effective spin system XAB2A'B'2, behaves as a much simpler XA2 system (where X = 13C, A = 15N, B = 1H), manifesting through a single narrow spectral peak. Additionally, we show that introducing spin-1 nuclei into the molecule and investigating J-spectra of 1H/D isotopologues of [15N2]-urea allows to study various isolated spin subsystems: XA2, (XA)B, and XB2 (here X = 15N, A = 1H, B = D), again greatly simplifying spectra analysis. The influence of the chemical exchange process on zero-field $J$-spectra for each urea solution is elucidated by theoretical studies, demonstrating solid agreement between results and simulations. This study shows the applicability of zero-field NMR to detect complex biomolecules in aqueous solutions, and it opens the means for future in vivo/in vitro biochemical investigations, particularly in biofluids with a high concentration of water.

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“…e motivation is to develop the growing use of reproducibly ordered media in analytical NMR spectroscopy [2,5,6]. e stretched/compressed gel approach is used in discriminating one enantiomer from another in chiral molecules [3,[7][8][9][10], identification and spectral separation of 13 C-labelled isotopomers/isotopologues for the quantification of the relative proportions in a mixture [11], distinguishing the NMR signals from inside cells from those outside, comparing the ordering of the environments [1,12], detecting heterogeneity by observing deviations from ideal spectral outcomes in gel-matrix systems [13], studying moiety mobility in small molecules [14], molecular structure refinement [15,16], and most recently in exploring the effects on metabolic rate and membrane transport that are brought about by distorting cells, a phenomenon called molecular mechanosensation [4].…”

Section: Motivationmentioning

confidence: 99%

What Are the Relative Intensities of the Components of NMR Spectral Multiplets from Quadrupolar Nuclei in Uniformly Anisotropic Media?

Elliott

Kuchel

2021

Concepts in Magnetic Resonance Part A

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Stretched hydrogels make uniformly anisotropic environments for quadrupolar nuclei such as 2H, 23Na, and 133Cs. Such surroundings cause the partial alignment of nuclear spin bearing ions and molecules that is sufficiently pronounced to alter the nuclear magnetic resonance spectra of the guest species. In most cases, resonance splittings are directly related to the spin quantum number I. The relative intensities of the components of the resonance multiplets can be inferred from basic quantum mechanics.

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NMR resonance splitting of urea in stretched hydrogels: Proton exchange and 1 H/ 2 H isotopologues

Cited by 7 publications

References 34 publications

Zero-Field NMR of Urea: Spin-Topology Engineering by Chemical Exchange

Zero-Field NMR of Urea: Spin-Topology Engineering by Chemical Exchange

Zero-field J-Spectroscopy of Urea: Spin-Topology Engineering by Chemical-Exchange

What Are the Relative Intensities of the Components of NMR Spectral Multiplets from Quadrupolar Nuclei in Uniformly Anisotropic Media?

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