脱氨基酸的气相红外光谱学
Jos Oomens1, Jeffrey D Steill, Britta Redlich
1FOM Institute for Plasma Physics Rijnhuizen, Edisonbaan 14, 3439MN Nieuwegein, The Netherlands. joso@rijnhuizen.nl
Journal of the American Chemical Society
|March 10, 2009
概括
气相红外光谱显示,氨基酸离子主要以碳酸盐的形式存在. 阿斯巴达酸和谷氨酸谱的扩展表明,脊柱和侧链碳酸盐之间存在质子桥梁.
科学领域:
- 物理化学 物理化学
- 频谱学是一种光谱学.
- 计算化学计算化学
背景情况:
- 氨基酸是基本的生物分子.
- 了解氨基酸的脱状态对于研究它们的化学性质和生物功能至关重要.
- 之前的研究已经提出了不同结构的deprotonated氨基酸.
研究的目的:
- 通过红外多光子解离 (IRMPD) 光谱学研究脱质氨基酸的气相结构.
- 将实验结果与密度函数理论 (DFT) 计算进行比较.
- 阐明各种氨基酸离子之间的结构差异.
主要方法:
- 气相红外多光子解离 (IRMPD) 光谱法用于记录去质子化氨基酸的光谱.
- 对于Asp,Cys,Glu,Phe,Ser,Trp和Tyr的结合基记录了红外光谱.
- 实验频谱与DFT级计算进行了比较.
主要成果:
- 大多数研究的氨基酸离子的IRMPD光谱表现出强烈的碳酸盐拉伸模式,表明碳酸盐结构.
- 氨酸的结合基被明确地确定为碳酸盐,而不是氧化物.
- 亚斯巴酸盐和谷氨酸酸盐离子表现出广泛的,未解决的光谱特征,这表明骨干和侧链碳酸盐之间存在质子桥梁.
结论:
- 这项研究证实了大多数研究的氨基酸的基的碳酸盐结构.
- 在阿斯巴酸盐和谷氨酸酸中观察到的光谱扩大归因于质子桥接,导致由于大振幅质子运动而导致广泛的光谱扩大.
- 这些发现提供了关于氨基酸离子在气相中的结构多样性和振动动态的见解.
相关概念视频
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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 broad and...
01:15Mass Spectrometry of Amines
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 molecular ion with an odd molecular weight. Amines undergo fragmentation through α cleavage, producing nitrogen-containing cations—iminium ions—and alkyl radicals. Mass spectra of aromatic and cyclic aliphatic amines exhibit strong molecular ion peaks, but acyclic aliphatic amines show...
01:26Spectroscopy of Carboxylic Acid Derivatives
Infrared spectroscopy is primarily used to determine the types of bonds and functional groups. In carboxylic acid derivatives, a typical carbonyl bond absorption is observed around 1650–1850 cm−1. For esters, the absorption is recorded at around 1740 cm−1, while acid halides show the absorption at about 1800 cm−1. Another acid derivative, the acid anhydrides, exhibit two carbonyl absorption around 1760 cm−1 and 1820 cm−1, arising from the symmetrical and unsymmetrical carbonyl vibration.
In the...
In 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...
01:30NMR and Mass Spectroscopy of Carboxylic Acids
In ¹H NMR spectroscopy, acidic protons (–COOH) of carboxylic acids are highly deshielded and absorb far downfield, at around 9–12 ppm. The chemical shift value depends on the concentration and solvent used.
While α protons of carboxylic acids absorb at 2–2.5 ppm, β protons absorb further upfield.
Carboxylic acids are easily identified by dissolving them in deuterium oxide, which results in a rapid exchange of the acidic protons with deuterium. This leads to the disappearance of the acidic...
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Carboxylic acids are easily identified by dissolving them in deuterium oxide, which results in a rapid exchange of the acidic protons with deuterium. This leads to the disappearance of the acidic...
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