19Fスピン拡散NMRを用いた脂質バイレイヤーにおけるペプチドオリゴメリゼーションの決定
Jarrod J Buffy1, Alan J Waring, Mei Hong
1Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA.
Journal of the American Chemical Society
|March 24, 2005
まとめ
新しい19Fスピン拡散マジック・アングル・スピニングNMR技術は,膜ペプチドの集積状態を正確に決定します. この方法は,プロテグリン-1抗菌ペプチドが主に脂質二重層のダイマーを形成することを明らかにします.
科学分野:
- 生物物理化学 生物物理化学
- 構造生物学 構造生物学とは
- 核磁共振 (NMR) スペクトロスコピー
背景:
- ペプチドの集積とオリゴメリゼーションは,イオンチャネルや抗菌ペプチドなどの膜タンパク質の機能に不可欠です.
- 膜ペプチド集積物の精密なオリゴメリック状態と分子数を決定することは,高解像度技術の限界のために困難でした.
- 膜ペプチドの集積を理解することは,それらの生物学的メカニズムを明らかにし,薬の開発に不可欠です.
研究 の 目的:
- 膜ペプチドのオリゴメリック状態の決定のための新しい19Fスピン拡散マジック・アングル・スピニングNMR技術を導入し,検証する.
- フォスホリピド二重層内の抗菌ペプチドプロテグリン-1の集積状態を定量化するために.
- ペプチド集積に関連する自由エネルギーなどの熱力学パラメータを計算するための方法を確立する.
主な方法:
- 19Fのスピン拡散マジック・アングル・スピニングのNMR実験の開発と応用.
- 方向的に異なる19Fスピン間の磁気化移転を利用して,分子近距離と集積サイズを検出しました.
- 既知の分子配列を持つ結晶モデル化合物を用いてその技術を検証し,POPCバイレイヤーのプロテグリン-1に適用した.
主要な成果:
- 19Fスピン拡散テクニックは,著しく高い効率 (約. 探査集積のための13Cスピン拡散と比較して500倍).
- プロテグリン-1への適用は,ペプチドが7.4mol%の濃度でPOPCバイレイヤーに主としてダイマーとして存在することを示しました.
- プロテグリン-1のダイマー形成の自由エネルギー (ΔG) は,既知のペプチド-膜相互作用と一致する -10.2 ± 2.3 kJ/molと推定されました.
結論:
- 開発された19Fスピン拡散NMR方法は,膜ペプチドのオリゴメリック状態を正確に決定するための高解像度アプローチを提供します.
- この技術は,脂質二重層環境におけるプロテグリン-1の二次状態を成功裏に定量化し,熱力学的な洞察を提供しました.
- この19F NMRアプローチは,膜結合ペプチドの構造的組織と機能的メカニズムを調査するための強力な新しいツールを提供します.
関連する概念動画
01:13¹H 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.
01:02¹H 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...
00:52¹H 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...
01:20¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
01:15¹H 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.
01:04¹³C NMR: ¹H–¹³C Decoupling
The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...