在低和功率下验证快速交换氨酸CEST效应的存在及其对APT量化的影响
Casey Sun1,2, Yu Zhao1,3, Zhongliang Zu1,3,4
1Vanderbilt University Institute of Imaging Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
Magnetic resonance in medicine
|June 15, 2023
概括
快速交换氨基CEST效应可能会高估氨基胺质子转移 (APT) 量化. 这项研究表明,氨基CEST如何影响APT测量和交换参数,这可能解释了先前研究结果的矛盾.
科学领域:
- 磁共振成像是一种磁共振成像技术.
- 生物医学工程 生物医学工程
- 化学交换和转移 (CEST) 图像成像 化学交换和转移 (CEST) 图像成像
背景情况:
- 准确量化胺质子转移 (APT) 效应和交换参数对于其应用至关重要.
- 之前的研究报告了在APT量化方面的相互矛盾的结果.
- 在APT量化中,快速交换氨基的CEST效应在很大程度上被忽视了,因为在低和功率下感知到的弱点.
研究的目的:
- 评估快速交换氨基CEST对低和功率APT量化的影响.
- 调查氨基CEST污染对APT效应和交换参数估计的影响.
- 了解先前的APT量化研究中相互矛盾的结果的来源.
主要方法:
- 采用使用低和高和功率的量化方法来区分APT与氨基CEST.
- 进行模拟以评估该方法能够分离APT和amin CEST效应的能力.
- 进行了动物实验,以确定氨和胺对3.5ppm的CEST信号的相对贡献.
- 在动物数据中应用了三种APT量化方法,其中含有不同级别的氨酸污染.
主要成果:
- 快速交换氨基CEST对APT效应的相对贡献随着和功率的增加而增加.
- 在9.4 T时,氨基CEST从APT效应的20%增加到40%,因为和功率从0.25增加到1μT.
- 模拟证实了该方法能够区分APT和amin CEST效应.
结论:
- 快速交换氨基CEST效应导致对APT效应的高估.
- 氨基CEST污染导致不准确的合胺度和胺-水交换率的估计.
- 这些发现表明,氨基CEST效应是导致先前报告的APT量化结果差异的一个重要因素.
相关概念视频
01:25Basicity of Heterocyclic Aromatic Amines
6.1K
Heterocyclic amines, where the N atom is a part of an alicyclic system, are similar in basicity to alkylamines. Interestingly, the heterocyclic amine having a nitrogen atom as part of an aromatic ring has much less basicity than its corresponding alicyclic counterpart. For this reason, as presented in Figure 1, piperidine (pKb = 2.8) is significantly more basic than pyridine (pKb = 8.8).
6.1K
01:19NMR Spectroscopy Of Amines
9.0K
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...
9.0K
01:18Effects of EDTA on End-Point Detection Methods
314
Different methods, such as visual observance of metal-ion indicators, spectroscopic techniques, and potentiometric methods, can determine the endpoint of an EDTA titration.
In the visual method, metal-ion indicators (metallochromic dyes), which have distinct colors in their free and complex forms, are added to the mixture to signal the titration's end point. They form stable complexes with metal ions, but these complexes are weaker than the corresponding metal–EDTA complexes. As a...
In the visual method, metal-ion indicators (metallochromic dyes), which have distinct colors in their free and complex forms, are added to the mixture to signal the titration's end point. They form stable complexes with metal ions, but these complexes are weaker than the corresponding metal–EDTA complexes. As a...
314
01:21Atomic Absorption Spectroscopy: Lab
498
For AAS measurements, samples must be introduced as clear solutions, often requiring extensive preliminary treatment to dissolve materials like soils, animal tissues, and minerals. Common methods for sample preparation include treatment with hot mineral acids, wet ashing, combustion in closed containers, high-temperature ashing, or fusion with reagents.
Solutions containing organic solvents, such as low-molecular-mass alcohols, esters, or ketones, enhance absorbances by increasing...
Solutions containing organic solvents, such as low-molecular-mass alcohols, esters, or ketones, enhance absorbances by increasing...
498
01:20¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
1.1K
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...
1.1K
01:15Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)
412
Insensitive Nuclei Enhanced by Polarization Transfer (INEPT) is an advanced Nuclear Magnetic Resonance (NMR) technique specifically designed to detect and enhance the signals of low-abundance nuclei, such as carbon-13 and nitrogen-15, in small molecules. The fundamental principle behind INEPT is the transfer of polarization from a more abundant and highly polarizable nucleus, typically hydrogen-1, to the low-abundance nucleus of interest. This process effectively boosts the NMR signal of the...
412