氨基酸的NMR晶体学研究
Ema Chaloupecká1, Václav Tyrpekl2, Kateřina Bártová3
1Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 160 00 Prague, Czech Republic; Department of Organic Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030, 128 40 Prague 2, Czech Republic.
Solid state nuclear magnetic resonance
|February 29, 2024
概括
这项研究为固体氨基酸提供了准确的化学转移数据,这对于推进NMR结晶学至关重要. 包括密度函数理论 (DFT) 在内的计算方法被验证为预测这些变化.
科学领域:
- 固态核磁共振 (NMR) 光谱学 固态核磁共振 (NMR) 光谱学
- 晶体学 晶体学是指结晶学.
- 计算化学的计算化学
- 材料科学 材料科学 材料科学
背景情况:
- 对于已知晶体结构的系统,NMR晶体学需要可靠的化学转移数据库.
- 准确的实验和计算数据对于开发和验证NMR结晶学方法至关重要.
- 氨基酸具有已知的多态结构,可以作为这种研究的理想模型系统.
研究的目的:
- 建立20种固体天然氨基酸的碳和化学转移的可靠数据库.
- 为了验证密度函数理论 (DFT) 的计算与已知晶体结构的系统的实验性NMR数据对比.
- 评估各种DFT函数的性能,以预测氨基酸中的NMR化学转移.
主要方法:
- 测量和分配20个固体天然氨基酸的碳和化学变化.
- 使用粉末X射线衍射测定多态晶体结构.
- 实验性NMR数据与使用GGA,元-GGA和混合函数计算的DFT计算的同otropic屏蔽的相关性.
主要成果:
- 对于碳屏蔽,PBE (一种GGA功能) 的表现很好,在应用混合功能校正时,有所改善.
- 混合DFT功能产生的NMR计算的最佳性能,当应用于结构优化在混合DFT水平.
- 高准确度的DFT计算使得以前未被分配的NMR信号能够被分配,包括来自单元细胞内的非等效分子的NMR信号.
结论:
- 经过验证的DFT方法可以准确地预测固体氨基酸中的NMR化学转移.
- 建立的数据库和验证的计算方法推动了NMR结晶学的应用.
- 这项工作促进了使用固态NMR的复杂有机材料的结构阐明.
相关概念视频
NMR Spectroscopy Of Amines
8.7K
In proton NMR spectroscopy, primary amines and secondary amines showcase their N–H protons as a broad signal in the chemical shift range between δ 0.5 and 5 ppm. The exact position in this range depends on several factors, including sample concentration, hydrogen bonding, and the type of solvent used. Since amine protons undergo fast proton exchange in solution, the protons are labile and therefore do not participate in any splitting with adjacent protons. Thus, the observed peak is...
8.7K
Structure of Amines
2.5K
The hybridized nitrogen atom in amines possesses a lone pair of electrons and is bound to three substituents with a bond angle of around 108°, which is less than the tetrahedral angle of 109.5°. However, the C–N–H bond angle is slightly larger at 112°, with a carbon–nitrogen bond length of 147 pm. This carbon–nitrogen bond length of of amines is longer than the carbon–oxygen bond of alcohols (143 pm) but shorter than alkanes’...
2.5K
Mass Spectrometry of Amines
4.2K
In mass spectroscopy, amines undergo fragmentation to give parent ions with odd molecule weights. This observed mass spectrum follows the nitrogen rule: a molecule with an odd number of nitrogen atoms produces a parent ion with an odd molecular weight. The remaining fragments have an even mass.
Amines undergo fragmentation through α cleavage, producing nitrogen-containing cations—iminium ions—and alkyl radicals. Mass spectra of aromatic and cyclic aliphatic amines exhibit...
Amines undergo fragmentation through α cleavage, producing nitrogen-containing cations—iminium ions—and alkyl radicals. Mass spectra of aromatic and cyclic aliphatic amines exhibit...
4.2K
Applications Of NMR In Biology
3.7K
Nuclear magnetic resonance (NMR) spectroscopy is a very valuable analytical technique for researchers. It has been used for more than 50 years as an analytical tool. F. Bloch and E. Purcell formulated NMR in 1946 and won the 1952 Nobel Prize in Physics for their work. Biological macromolecules such as proteins, nucleic acids, lipids, and organic molecules including pharmaceutical compounds, can be studied using this versatile tool that exploits the magnetic properties of certain nuclei.
3.7K
Amino acids
88.8K
Amino acids are the monomers that comprise proteins. Each amino acid has the same fundamental structure, which consists of a central carbon atom, or the alpha (α) carbon, bonded to an amino group (NH2), a carboxyl group (COOH), and to a hydrogen atom. Every amino acid also has another atom or group of atoms bonded to the central atom known as the R group. There are 20 common amino acids present in proteins, each with a different R group. Variation in the amino acid sequence is responsible...
88.8K
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
839
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...
839


