固体NMRスペクトロスコーピーのヘテロ核 (15) N-(17) Oおよび (13) C-(17) Oの接続性と近接性を探査する
Ivan Hung1, Anne-Christine Uldry, Johanna Becker-Baldus
1Department of Physics, University of Warwick, Coventry, UK.
Journal of the American Chemical Society
|January 14, 2009
まとめ
この研究は,窒素-酸素 (15N-17O) 二極およびグリシンとウラシルのJ結合を正確に測定するための新しい固体NMR方法を実証しています. これらのテクニックは,これらの重要な分子に対する正確な構造と結合の洞察を提供します.
科学分野:
- 固体核磁共振 (NMR) スペクトロスコーピーは,固体核磁共振 (NMR) スペクトロスコーピーを用います.
- 量子化学とコンピューティングモデリング
- 材料科学と構造分析について
背景:
- 原子核間結合の正確な決定は,固体材料の分子構造と結合を理解するために極めて重要です.
- ヘテロ核二極結合とJ結合は,それぞれ,スルースペースとスルーボンドの相互作用に関するユニークな情報を提供します.
- 固体における15N−17O結合を測定する以前の方法には,精度と適用性の限界がある.
研究 の 目的:
- (15) N - 17 O 二極および J カップリングの測定のための高度な固体 NMR 実験を開発し,検証する.
- 構造的および電子的特性を評価するために,同位素で標識されたグリシンとウラシルにこれらの方法を適用する.
- NMRの方法論を検証するために,実験結果を理論的な計算と比較する.
主な方法:
- R(3) -HMQC,REDOR,およびREAPDORを含むヘテロ核固体マジック・アングルスピニング (MAS) NMR実験の実施.
- 使用された同位体濃縮サンプル: [ 2 H ] NH 3 ] 1 - 13 C , 15 N , 17 O 2 ] グリシン 2 HCl と [ 15 N 2 ] 17 O 2 ] ウラシル .
- ヘテロ核とホモ核のスピンエコー実験の分析によるJカップリングの定量化 (S(Q) ((tau) = S(HET) ((tau) /S(HOM) ((tau)).
- ジオメトリック的に最適化された結晶構造を持つCASTEPコードを用いた計算式Jカップリング計算.
主要な成果:
- 2D (15) N-(17) O相関スペクトルを取得し,ピーク強度が (15) N-(17) O二極結合の大きさを反映した.
- グリシン2HClの実験的二極結合は,結晶構造から得られた値と良好な一致 (+/-20%以内) を示した.
- グリシン2HCl (24.7-25.3 Hz) の測定された単一結合 J カップリング ((1) J (((CO)) とウラシル (5.1 +/- 0.6 Hz) の水素結合媒介 J カップリング.
- 判定された2結合の分子内J結合: (2) J(OO) = 8.8 +/- 0.9 Hz グリシン.2HCl と (2) J(N1,N3) = 2.7 +/- 0.1 Hz ウラシル.
- 実験とCASTEPで計算されたJカップリングの間で,グリシンとウラシルの両方に優れた一致が観察されました.
結論:
- 提出された固体NMR技術は,15N-(17) O二極およびJ結合の特徴づけに有効です.
- この結果は,これらのNMRメソッドの精度を検証し,グリシンとウラシルの構造と結合に関する詳細な情報を提供します.
- この研究は,実験的なNMRと,固体構造の解明のための計算方法の組み合わせの力を強調しています.
関連する概念動画
2D NMR: Overview of Heteronuclear Correlation Techniques
Heteronuclear correlation spectroscopy is an analytical technique that investigates the coupling between different types of nuclei, often a proton and an X-nucleus, such as carbon-13 or nitrogen-15. This method is commonly used in nuclear magnetic resonance (NMR) spectroscopy to gain insights into complex chemical compounds' structural and compositional aspects. A typical heteronuclear correlation spectrum displays X-nucleus chemical shifts on one axis and a proton spectrum on the other axis.
2D NMR: Overview of Homonuclear Correlation Techniques
Homonuclear correlation spectroscopy (COSY) is a powerful technique used in Nuclear Magnetic Resonance (NMR) spectroscopy to study the correlations between nuclei of the same type within a molecule. It provides information about scalar couplings between adjacent nuclei, which helps determine connectivity and structural information. There are several COSY variants, each with its unique strengths and experimental parameters.
COSY90 is the standard two-dimensional (2D) COSY experiment that...
COSY90 is the standard two-dimensional (2D) COSY experiment that...
2D NMR: Heteronuclear Single-Quantum Correlation Spectroscopy (HSQC)
Heteronuclear single-quantum correlation spectroscopy (HSQC) is a 2D NMR technique that reveals one-bond correlations between hydrogen and a heteronucleus. The HSQC experiment is similar to the heteronuclear correlation experiment (HETCOR) but is more sensitive. In the HSQC spectrum, the proton chemical shift is plotted on the horizontal F2 axis, while the 13C chemical shift is plotted on the vertical F1 axis. The corresponding proton and 13C spectra are also shown. The HSQC contour plot does...
NMR Spectroscopy: Spin–Spin Coupling
The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved in...
¹H NMR: Long-Range Coupling
The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
¹H NMR: Interpreting Distorted and Overlapping Signals
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...


