定量旋转回波双共振碳-13 自旋簇。
Quantitative rotational-echo double resonance for Carbon-13 spin clusters.
机构信息
Department of Chemistry, Washington University, St. Louis, MO 63130, USA; Faculty of Medicine, Oita University, Oita 879-5593, Japan.
Department of Chemistry, Washington University, St. Louis, MO 63130, USA.
出版信息
J Magn Reson. 2021 Sep;330:107043. doi: 10.1016/j.jmr.2021.107043. Epub 2021 Jul 22.
By using only half of the total evolution time for dephasing pulses, C{N} rotational-echo double resonance (REDOR) for clusters of C spins (RDX) results in the same universal REDOR behavior as observed for isolated C-N pairs. RDX combines Hahn echoes with solid echoes to suppress interference from scalar J couplings. This is crucial for long evolution times. The modified version (which we call RDX24) makes RDX quantitative for C clusters. We apply this scheme to human embryonic kidney cells labeled in culture by L-[C -N]-glutamine. We quantitatively characterize three separate nitrogen isotopic enrichments for: (i) the alpha nitrogens of glutamine residues in proteins (including the residues of the five amino acids synthesized from glutamine); (ii) the alpha nitrogens of the five amino-acid residues synthesized from glucose, together with those of the nine essential amino acids added to the growth medium; and (iii) the side-chain nitrogens of glutamine (and of asparagine derived from glutamine).
通过仅使用去相脉冲总弛豫时间的一半，C{N} 旋转回波双共振（REDOR）对于 C 自旋簇（RDX）的结果与观察到的孤立 C-N 对的通用 REDOR 行为相同。RDX 将哈恩回波与固体回波结合使用，以抑制来自标量 J 耦合的干扰。这对于长弛豫时间至关重要。经过修改的版本（我们称为 RDX24）使 RDX 对于 C 簇具有定量性。我们将此方案应用于通过 L-[C-N]-谷氨酰胺在培养物中标记的人胚肾细胞。我们对以下三个不同的氮同位素富集进行了定量描述：（i）蛋白质中谷氨酰胺残基的α氮（包括从谷氨酰胺合成的五个氨基酸的残基）；（ii）从葡萄糖合成的五个氨基酸残基的α氮，以及添加到生长培养基中的九个必需氨基酸的α氮；（iii）谷氨酰胺（以及从谷氨酰胺衍生的天冬酰胺）的侧链氮。
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