在功能或晶体学上不对称的同位体中,溶液核磁共振对称性的证据
Raquel Godoy-Ruiz1, Anna Krejcirikova, D Travis Gallagher
1Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA.
Journal of the American Chemical Society
|November 15, 2011
概括
结构研究经常质疑水晶形状是否反映了真正的蛋白质功能. 这项研究使用核磁共振 (NMR) 来显示几个同质蛋白在没有连接体的情况下表现出对称性,从而挑战了晶体结构的解释.
科学领域:
- 生物化学 生物化学
- 结构生物学 结构生物学
- 生物物理学的生物物理.
背景情况:
- 对同类寡合蛋白质的结构研究经常面临的挑战是验证晶体构造是否代表功能相关的结构.
- 同型寡合体中的不对称构造可能来自固有的蛋白质特性或晶体包装工件.
- 区分内在不对称性和结晶诱导的工件对于理解蛋白质功能至关重要.
研究的目的:
- 为了研究溶液中的同质蛋白质的构造对称性,独立于晶体包装效应.
- 为了确定在晶体结构中观察到的不对称性是否具有功能相关性或是文物.
- 用溶液状态NMR.提供支持或反对同位体蛋白质内在对称性的证据.
主要方法:
- 使用基于甲基的核磁共振 (NMR) 谱学.
- 在缺乏连接体的情况下分析同位体蛋白质系统.
- 将溶液NMR数据与现有的X射线晶体结构进行比较.
主要成果:
- 证据表明,在几个同位体蛋白质中,在它们的无连接体状态下,发现了构造对称性的证据.
- 观察到的溶液对称性与在一些可用的X射线结构中观察到的不对称性形成鲜明对比.
- 这表明晶体包装可以诱导或稳定不对称的形状.
结论:
- 溶液NMR光谱是评估同类寡合蛋白质内在对称性的强大工具.
- 晶体结构可能并不总是代表溶液中同位体的功能相关的对称构造.
- 该研究强调了补充结构技术的重要性,以准确确定蛋白质结构功能关系.
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.
01:162D NMR: Overview of Homonuclear Correlation Techniques
Homonuclear correlation spectroscopy (COSY) is a powerful technique used in Nuclear Magnetic Resonance (NMR) spectroscopy to study the correlations between nuclei of the same type within a molecule. It provides information about scalar couplings between adjacent nuclei, which helps determine connectivity and structural information. There are several COSY variants, each with its unique strengths and experimental parameters.
COSY90 is the standard two-dimensional (2D) COSY experiment that...
COSY90 is the standard two-dimensional (2D) COSY experiment that...
01:062D NMR: Homonuclear Correlation Spectroscopy (COSY)
Homonuclear correlation spectroscopy, or COSY, is a 2-dimensional NMR technique that provides information about coupled protons. Typically, the geminal and vicinal coupling are observed. For example, consider the COSY spectrum of ethyl acetate, where its 1D proton NMR spectrum is plotted along the vertical and horizontal axes with their corresponding chemical shift scale. Three spots on the diagonal corresponding to the three peaks in the 1D proton spectrum are called diagonal peaks. The COSY...
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...
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...
02:52Stereoisomerism
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...