DQC STUDY OF THE NITROXIDE BIRADICALS USED IN DNP

DNP 中使用的氮氧双自由基的 DQC 研究

• 批准号: 7602630
• 负责人: PETER P BORBAT
• 金额: $ 0.01万
• 依托单位: CORNELL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-01 至 2008-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7602630
• 关键词: 2,4-Dinitrophenol; Computer Retrieval of Information on Scientific Projects Database; Deer; Dimethyl Sulfoxide; Electron Spin Resonance Spectroscopy; Electrons; Frequencies; Funding; Glycerol; Grant; Hand; Institution; Length; Measures; Methods; Nuclear; Personal Satisfaction; Physics; Process; Purpose; Range; Reporting; Research; Research Personnel; Resources; Services; Signal Transduction; Solvents; Source; Structure; Techniques; United States National Institutes of Health; base; improved; irradiation; novel strategies; research study; water solution

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. It was recently found that nitroxide biradicals are efficient in low concentrations in DNP, a method that has long been used to improve SNR in NMR. The modern DNP experiment at MIT is based on irradiation of nitroxides with 140 or 250 GHz gyrotron sources, leading to signal enhancements of up to 400. The underlying physics is described by a three spin process, with the two electron spins spaced at the nuclear frequency. The use of biradicals is a new approach to an old technique based on paramagnetic species bearing a single electron spin in relatively high concentration. In a recent study bis-TEMPO n-ethyleneglycol (BTnE) biradicals (n=2, 3, or 4) were employed. The largest enhancement was observed for n=2 with 5 to 10 mM of electron spins. The purpose of the service request was two-fold: 1) to provide distances for several nitroxide biradicals of short length, ranging from 10 to 18 A; 2) to obtain mutual orientations of nitroxide hf tensors. A practical short distance limit for DEER is ca. 17-20 A, due to weak B1. On the other hand, DQC featuring B1 of 30 G or greater could be used to measure shorter distances. We applied DQC to BTnE biradicals in DMSO and glycerol-water solutions. Also, three other biradicals of rigid structure were studied. These include BTXA, BTOX, and BTUrea. BTOX and BTXA DQC gave clearly resolved dipolar spectra, from which the distances were easily inferred. BTnE proved to be more flexible, and its dipolar spectra were unresolved. The distances ranged from 11 to 16 ¿ and were well within the margin of error for the distances reported by W-band CW-ESR spectroscopy in perduterated solvents, although DQC did allow determination of distances in all cases. The study will be continued to obtain 2D-DQC spectra in order to determine the orientation of the hf tensors.

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 最近发现，氮氧双自由基在低浓度的DNP中是有效的，这是一种长期用于提高NMR中SNR的方法。 麻省理工学院的现代DNP实验是基于用140或250 GHz回旋管源照射氮氧化物，导致信号增强高达400。 基本的物理学是由三自旋过程描述的，其中两个电子自旋以核频率间隔开。双自由基的使用是一种新的方法，一个老的技术的基础上，顺磁性物种轴承一个电子自旋在相对较高的浓度。在最近的一项研究中，使用了双-TEMPO n-乙二醇（BTnE）双自由基（n=2、3或4）。对于n=2，在5至10 mM的电子自旋下观察到最大的增强。服务请求的目的有两个方面：1）为几个短长度的氮氧双自由基提供距离，范围为10至18 A; 2）获得氮氧hf张量的相互取向。鹿的实际短距离限制是大约。17-20 A，由于弱B1。另一方面，B1为30 G或更大的DQC可用于测量更短的距离。我们将DQC应用于DMSO和甘油-水溶液中的BTnE双自由基。另外，还研究了其它三种刚性结构的双自由基。这些包括BTXA，BTOX和BTURea。 BTOX和BTXA DQC给出了清晰分辨的偶极光谱，从中可以很容易地推断出距离。BTnE被证明是更灵活的，其偶极光谱是无法分辨的。距离范围从11到16 º，并且完全在W-波段CW-ESR光谱法在全氘代溶剂中报告的距离的误差范围内，尽管DQC确实允许在所有情况下测定距离。 将继续研究以获得2D-DQC光谱，从而确定hf张量的方向。