大分子组合的缓慢扩散通过一种新的脉冲场梯度NMR方法
Fabien Ferrage1, Manuela Zoonens, Dror E Warschawski
1Département de Chimie, associé au CNRS, Ecole Normale Supérieure, 24 rue Lhomond, F-75231 Paris Cedex 05, France.
Journal of the American Chemical Society
|February 27, 2003
概括
一种新的脉冲场梯度NMR方法可以精确测量像蛋白质复合体这样的大分子的扩散系数. 这种技术提高了扩散间隔的持续时间,允许分析以前难以研究的宏分子组合.
科学领域:
- 生物物理化学 生物物理化学
- 核磁共振 (NMR) 光谱学 核磁共振 (NMR) 光谱学
- 膜蛋白的特征鉴定方法
背景情况:
- 整体膜蛋白及其复合体对于细胞功能至关重要,但由于它们的疏水性质,研究它们具有挑战性.
- 精确测量转化扩散系数对于理解分子相互作用和组装动态至关重要.
- 现有的NMR方法通常在测量大或缓慢移动的宏分子组件的扩散方面存在局限性.
研究的目的:
- 开发和验证一种用于测量转化扩散系数的新型脉冲场梯度NMR方法.
- 为了使宏分子组合的研究,扩散系数低于10~10m~2s~-1).
- 将该方法应用于整体膜蛋白复合体和其他大型生物分子.
主要方法:
- 利用一种新的脉冲场梯度NMR方法,将分子定位信息存储在长自旋格子放松时间同位素中.
- 与标准方法相比,扩散间隔的持续时间大约增加了一个数量级.
- 将该技术应用于细菌外膜蛋白A (tOmpA) 复合体和重组人体tRNA.
主要成果:
- 成功测量了tompA/C(8) E(4) 复合物的扩散系数 (约. 45 kDa) 作为D = (4.99 ± 0.07) x 10(-11) m(2) s(-1).因此,我们可以使用
- 确定了人类tRNA的扩散系数 ((3) ((Lys)) (大约. 24 kDa) 作为D = (1.05 ± 0.015) x 10 -10 m2) s-1). 这样,我们可以得到D = (1.05 ± 0.015) x 10 -10 m2) s-1.
- 结果与补充生物物理技术 (如尺寸排除色谱和超离心) 一致.
结论:
- 新的NMR方法有效测量宏分子组合的扩散系数,包括不可分割的膜蛋白质复合体.
- 这种技术克服了用于研究缓慢扩散分子 (>25 kDa) 的标准NMR方法的局限性.
- 开发的方法为溶液中大型生物分子系统的生物物理特征提供了有价值的工具.
相关概念视频
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...
01:12Two-Dimensional (2D) NMR: Overview
The 1D NMR spectrum of large and complex molecules like natural products has complicated splitting patterns and overlapping signals, which can be easily interpreted using 2-dimensional (2D) NMR. Unlike 1D NMR, 2D NMR has two frequency axes that provide the coupling information between the nucleus A and nucleus B in a molecule. The process from which 2D spectra are obtained has four steps.
The first step is the preparation period, during which nucleus A is excited with a radiofrequency pulse.
The first step is the preparation period, during which nucleus A is excited with a radiofrequency pulse.
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...
01:17NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences
A pulse is a short burst of radio waves distributed over a range of frequencies that simultaneously excites all the nuclei in the sample. Upon passing a radio frequency pulse along the x-axis, the nuclei absorb energy corresponding to their Larmor frequencies and achieve resonance. This shifts the net magnetization vector from the z-axis toward the transverse plane. This angle of rotation of the magnetization vector, or the flip angle, is proportional to the duration and intensity of the pulse.
01:12Double Resonance Techniques: Overview
Double resonance techniques in Nuclear Magnetic Resonance (NMR) spectroscopy involve the simultaneous application of two different frequencies or radiofrequency pulses to manipulate and observe two distinct nuclear spins. One important application of double resonance is spin decoupling, which selectively suppresses coupling with one type of nucleus while observing the NMR signal from another nucleus, simplifying the spectrum and enhancing resolution.
Spin decoupling is usually achieved by...
Spin decoupling is usually achieved by...