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Influence of 13C Isotopic Labeling Location on Dynamic Nuclear Polarization of Acetate.

ABSTRACT: Dynamic nuclear polarization (DNP) via the dissolution method has alleviated the insensitivity problem in liquid-state nuclear magnetic resonance (NMR) spectroscopy by amplifying the signals by several thousand-fold. This NMR signal amplification process emanates from the microwave-mediated transfer of high electron spin alignment to the nuclear spins at high magnetic field and cryogenic temperature. Since the interplay between the electrons and nuclei is crucial, the chemical composition of a DNP sample such as the type of free radical used, glassing solvents, or the nature of the target nuclei can significantly affect the NMR signal enhancement levels that can be attained with DNP. Herein, we have investigated the influence of 13C isotopic labeling location on the DNP of a model 13C compound, sodium acetate, at 3.35 T and 1.4 K using the narrow electron spin resonance (ESR) line width free radical trityl OX063. Our results show that the carboxyl 13C spins yielded about twice the polarization produced in methyl 13C spins. Deuteration of the methyl 13C group, while proven beneficial in the liquid-state, did not produce an improvement in the 13C polarization level at cryogenic conditions. In fact, a slight reduction of the solid-state 13C polarization was observed when 2H spins are present in the methyl group. Furthermore, our data reveal that there is a close correlation between the solid-state 13C T1 relaxation times of these samples and the relative 13C polarization levels. The overall results suggest the achievable solid-state polarization of 13C acetate is directly affected by the location of the 13C isotopic labeling via the possible interplay of nuclear relaxation leakage factor and cross-talks between nuclear Zeeman reservoirs in DNP.

SUBMITTER: Niedbalski P

PROVIDER: S-EPMC6260835 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

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Influence of <sup>13</sup>C Isotopic Labeling Location on Dynamic Nuclear Polarization of Acetate.

Niedbalski Peter P Parish Christopher C Kiswandhi Andhika A Kovacs Zoltan Z Lumata Lloyd L

The journal of physical chemistry. A 20170424 17

Dynamic nuclear polarization (DNP) via the dissolution method has alleviated the insensitivity problem in liquid-state nuclear magnetic resonance (NMR) spectroscopy by amplifying the signals by several thousand-fold. This NMR signal amplification process emanates from the microwave-mediated transfer of high electron spin alignment to the nuclear spins at high magnetic field and cryogenic temperature. Since the interplay between the electrons and nuclei is crucial, the chemical composition of a D ...[more]

PMID: 28422500

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Project description:Non-enzymatic glycation of proteins is a post-translational modification produced by a reaction between reducing sugars and amino groups located in lysine and arginine residues or in the N-terminal position. This modification plays a relevant role in medicine and food industry. In the clinical field, this undesired role is directly linked to blood glucose concentration and therefore to pathological conditions derived from hyperglycemia (>11 mm glucose) such as diabetes mellitus or renal failure. An approach for qualitative and quantitative analysis of glycated proteins is here proposed to achieve the three information levels for their complete characterization. These are: 1) identification of glycated proteins, 2) elucidation of sugar attachment sites, and 3) quantitative analysis to compare glycemic states. Qualitative analysis was carried out by tandem mass spectrometry after endoproteinase Glu-C digestion and boronate affinity chromatography for isolation of glycated peptides. For this purpose, two MS operational modes were used: higher energy collisional dissociation-MS2 and CID-MS3 by neutral loss scan monitoring of two selective neutral losses (162.05 and 84.04 Da for the glucose cleavage and an intermediate rearrangement of the glucose moiety). On the other hand, quantitative analysis was based on labeling of proteins with [(13)C(6)]glucose incubation to evaluate the native glycated proteins labeled with [(12)C(6)]glucose. As glycation is chemoselective, it is exclusively occurring in potential targets for in vivo modifications. This approach, named glycation isotopic labeling, enabled differentiation of glycated peptides labeled with both isotopic forms resulting from enzymatic digestion by mass spectrometry (6-Da mass shift/glycation site). The strategy was then applied to a reference plasma sample, revealing the detection of 50 glycated proteins and 161 sugar attachment positions with identification of preferential glycation sites for each protein. A predictive approach was also tested to detect potential glycation sites under high glucose concentration.

Dataset Information

Influence of 13C Isotopic Labeling Location on Dynamic Nuclear Polarization of Acetate.

Publications

Influence of <sup>13</sup>C Isotopic Labeling Location on Dynamic Nuclear Polarization of Acetate.

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