使用19F旋转扩散NMR确定脂质双层中的类寡合化
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
概括
一种新的19F旋转扩散神奇角度旋转的NMR技术准确地确定了膜聚合状态. 这种方法揭示了protegrin-1抗菌主要在脂质双层中形成二次体.
科学领域:
- 生物物理化学 生物物理化学
- 结构生物学 结构生物学
- 核磁共振 (NMR) 光谱学 核磁共振 (NMR) 光谱学
背景情况:
- 聚和寡聚化对于膜蛋白的功能至关重要,如离子通道和抗菌.
- 由于高分辨率技术的局限性,确定膜聚合物中精确的寡合体状态和分子数量一直是具有挑战性的.
- 了解膜聚合对于阐明它们的生物机制和药物开发至关重要.
研究的目的:
- 引入和验证一种新的19F旋转扩散神奇角度旋转NMR技术,用于确定膜的寡合状态.
- 量化脂双层中抗微生物蛋白-1的聚合状态.
- 建立一种计算热力学参数的方法,例如与聚相关的自由能量.
主要方法:
- 开发和应用一个19F旋转扩散神奇角度旋转的NMR实验.
- 在方向上不同的19F旋转之间利用磁化转移来探测分子近距离和聚合体大小.
- 使用已知分子排列的晶体模型化合物验证了该技术,并将其应用于POPC双层中的protegrin-1.
主要成果:
- 19F旋转扩散技术证明了显著更高的效率 (大约. 500倍) 与探测聚合的13C旋转扩散相比.
- 对蛋白质蛋白-1的应用表明,该主要存在于POPC双层中的二极体,度为7.4mol%.
- 估计Protegrin-1的二聚体形成的自由能量 (ΔG) 为-10.2 ± 2.3 kJ/mol,与已知的-膜相互作用一致.
结论:
- 开发的19F自旋扩散NMR方法提供了一种高分辨率的方法,可以准确地确定膜的寡合状态.
- 这种技术成功地量化了蛋白质蛋白-1在脂质双层环境中的二维状态,并提供了热力学见解.
- 这种19F核磁共振方法为研究膜结合的结构组织和功能机制提供了一个强大的新工具.
相关概念视频
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...