部分的に指向したサンプルの固体状態NMRスペクトロスコーピーのアミロイド繊維に対する絶対的な構造的制約
1Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Building 5, Room 112, Bethesda, Maryland 20892-0520, USA.
Journal of the American Chemical Society
|April 9, 2004
まとめ
固体NMRは,アミロイド繊維の分子レベルの構造的な洞察を提供します. この方法は,13C NMRスペクトルの魔法の角度回転サイドバンドパターンを分析することによって,繊維の方向性を決定します.
科学分野:
- バイオフィジックス 生物物理学
- 構造生物学 構造生物学とは
- 神経科学は神経科学である.
背景:
- アミロイド繊維は,アルツハイマー病などの神経変性疾患と関連しています.
- アミロイド線維の正確な分子構造を決定することは,病気のメカニズムを理解するために非常に重要です.
- 固体核磁共振 (NMR) は,タンパク質の構造を研究するための強力な技術です.
研究 の 目的:
- 絶対的な分子レベルの構造情報を,部分的に指向されたアミロイド繊維の固体状態のNMRから得ることができることを示すために.
- カーボニル13C化学シフトアニソトロピー (CSA) テンソールに対する繊維軸の向きを決定する.
- アミロイド繊維の構造モデルを検証する.
主な方法:
- 13C NMRスペクトルにおけるマジック・アングル・スピニング (MAS) サイドバンドパターンを利用する.
- 平面基板に堆積した繊維を分析して,アニゾトロプ的方向分布を作成します.
- アベタ1-40繊維におけるVal12のカルボニルCSAテンソールに対する繊維軸の方向を測定する.
主要な成果:
- 絶対的な構造情報は,固体NMR測定から得られた.
- カーボニル13C CSAテンソールに対する繊維軸の方向を決定した.
- Abeta1-40繊維の実験結果は,平行ベータシート構造モデルの予測と一致しています.
結論:
- 部分的に指向されたアミロイド繊維の固体状態のNMRは,絶対的な構造データを生成します.
- この方法は,分子テンソールと比較して繊維の方向を正確に決定します.
- このテクニックは,アミロイド線維の構造モデルの検証と精錬に使用できます.
関連する概念動画
Globular and Fibrous Proteins
Many proteins can be classified into two distinct subtypes - globular or fibrous. These two types differ in their shapes and solubilities.
Globular proteins are also known as spheroproteins and typically are approximately round in shape. They contain a mix of amino acid types and contain differing sequences in their primary structures. Globular proteins have many different functions, such as enzymes, cellular messengers, and molecular transporters. These roles often require the proteins to be...
Globular proteins are also known as spheroproteins and typically are approximately round in shape. They contain a mix of amino acid types and contain differing sequences in their primary structures. Globular proteins have many different functions, such as enzymes, cellular messengers, and molecular transporters. These roles often require the proteins to be...
¹H NMR: Complex Splitting
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.
NMR Spectroscopy Of Amines
In proton NMR spectroscopy, primary amines and secondary amines showcase their N–H protons as a broad signal in the chemical shift range between δ 0.5 and 5 ppm. The exact position in this range depends on several factors, including sample concentration, hydrogen bonding, and the type of solvent used. Since amine protons undergo fast proton exchange in solution, the protons are labile and therefore do not participate in any splitting with adjacent protons. Thus, the observed peak is broad and...
Other Nuclides: 31P, 19F, 15N NMR
Many organic, inorganic, and biological molecules contain spin-half nuclei such as nitrogen-15, fluorine-19, and phosphorus-31. As a result, NMR studies of these nuclei have found extensive applications in chemical and biological research.
While fluorine-19 and phosphorous-31 have high natural abundances (100%) and positive gyromagnetic ratios, nitrogen-15 has a low natural abundance and a negative gyromagnetic ratio. However, nitrogen-15 is still preferred over nitrogen-14 (which has a high...
While fluorine-19 and phosphorous-31 have high natural abundances (100%) and positive gyromagnetic ratios, nitrogen-15 has a low natural abundance and a negative gyromagnetic ratio. However, nitrogen-15 is still preferred over nitrogen-14 (which has a high...


