膜双层的弹性变形通过NMR放松探测
Michael F Brown1, Robin L Thurmond, Steven W Dodd
1Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA. mfbrown@u.arizona.edu
Journal of the American Chemical Society
|July 11, 2002
概括
核磁共振显示,脂质双层是有序的流体. 结合的顺序参数和放松研究量化了双层软度,提供了对膜弹性和脂质相互作用的见解.
科学领域:
- 生物物理学的生物物理.
- 核磁共振光谱法 核磁共振光谱法
- 膜生物物理学 膜生物物理学
背景情况:
- 脂质双层构成了细胞膜的基础.
- 核磁共振光谱 (2H核磁共振) 对于理解脂质动态至关重要.
- 分段顺序参数 (S(CD)) 和旋转放松率 (R(1Z)) 提供了对脂质结构和运动的见解.
研究的目的:
- 使用组合的 (2) H NMR 顺序参数和放松测量,全面描述液晶 (Lα) 状态的脂质.
- 为了研究脂质结构,动力学和双层粘弹性特性之间的关系.
- 开发一种新的模型,解释脂质双层中的NMR放松行为.
主要方法:
- 使用 (2)H NMR光谱测量脂的细分顺序参数 (S(CD)).
- 进行了自旋格子放松率 (R(1Z)) 研究,以探测脂质动态.
- 应用了一种新的复合膜变形模型来分析放松的频率和角度依赖.
主要成果:
- 脂质双层是有序的流体,脂在接口和液态碳化合物链上被移植.
- R{1Z}和S{CD}之间的平方规律依赖表明双层波动缓慢.
- 核磁共振放松是由脂酸长度,头组,洗剂和胆固醇调节的,影响双层软度.
结论:
- 核磁共振放松研究揭示了膜脂质在兆赫兹频率上的粘弹性特性.
- 弹性变形的概念在中观尺度 (平面厚度) 上是相关的.
- 结合R ((1Z) 和S ((CD) 研究作为膜弹性计,量化双层曲刚性和面积弹性模量.
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...
01:08IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations
Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single stretching vibration...
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.
01:12Double 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...