HIGH FIELD/HIGH FREQUENCY ESR FOR STUDYING DNP IN BIOMEMBRANES

用于研究生物膜中 DNP 的高场/高频 ESR

• 批准号: 8364114
• 负责人: ANN E MCDERMOTT
• 金额: $ 1万
• 依托单位: CORNELL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2012-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8364114
• 关键词: Cell Nucleus; Coupled; Electron Spin Resonance Spectroscopy; Electrons; Frequencies; Funding; Grant; Integral Membrane Protein; Location; Magnetic Resonance; Magnetic Resonance Imaging; Medicine; Membrane; Membrane Proteins; National Center for Research Resources; Nuclear; Positioning Attribute; Principal Investigator; Protein Fragment; Protons; Relaxation; Research; Research Infrastructure; Resolution; Resources; Sampling; Signal Transduction; Source; Techniques; Technology; United States National Institutes of Health; Universities; Work; cost; flexibility; improved; insight; interest; irradiation; magnetic field; microwave electromagnetic radiation; research study; solid state nuclear magnetic resonance; structural biology; tool

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Dynamic Nuclear Polarization (DNP), which has been well-known since the early years of magnetic resonance, is now becoming a powerful tool to improve the sensitivity and resolution for NMR and MRI techniques in structural biology and medicine. Transfer of polarization from unpaired electron spins to coupled nuclear spins (protons, 15N, 13C) results in an enhancement of the NMR signal. This enhancement could be as high as three orders of magnitude for solid state NMR. However, the current theoretical understanding for DNP is incomplete and ACERT, with our High Field ESR technology and expertise in ESR relaxation, is in a good position to better understand this phenomenon. Observation of DNP effects in magnetic fields routinely used for NMR experiments (3  20 Tesla) requires microwave irradiation of the sample at the corresponding High Field/High Frequency ESR range: 90  600 GHz. ACERT has a unique capability to carry out ESR experiments at a wide range of frequencies. Prof. McDermott's (Columbia University) interest in DNP is focused on membrane proteins with attached radicals. It has been recently found that nitroxide biradicals with relatively short interspin distances (d 10¿) are very efficient polarizing agents. Moreover, it has been shown that rigid biradicals are even more powerful polarizing agents than biradicals with flexible tethers. However, there is much that is not well understood about the biradicals and how they work for DNP. In particular, the exact mechanism of DNP relaxation enhancement by multiradicals is still unclear. A detailed study of ESR relaxation for existing and perspective DNP polarizing agents at high frequencies will provide valuable insights into the DNP phenomenon. To obtain DNP enhanced NMR signals from paramagnetic nuclei embedded into the hydrophobic core of the membrane, the nuclei should be accessible for the polarizing agent. ESR spectroscopy, and High Field ESR spectroscopy in particular, can easily determine the depth location of possible polarizing agents in the membrane and predict the accessibility of various transmembrane protein fragments.

该子项目是利用资源的众多研究子项目之一 由 NIH/NCRR 资助的中心拨款提供。子项目的主要支持 并且子项目的主要研究者可能是由其他来源提供的， 包括其他 NIH 来源。 子项目可能列出的总成本 代表子项目使用的中心基础设施的估计数量， NCRR 赠款不直接向子项目或子项目工作人员提供资金。 动态核极化 (DNP) 自磁共振诞生之初就广为人知，现在正成为提高结构生物学和医学领域 NMR 和 MRI 技术灵敏度和分辨率的有力工具。极化从不成对电子自旋转移到耦合核自旋（质子、15N、13C）导致 NMR 信号增强。对于固态核磁共振来说，这种增强可能高达三个数量级。然而，目前对 DNP 的理论理解并不完整，而 ACERT 凭借我们的高场 ESR 技术和 ESR 弛豫方面的专业知识，能够更好地理解这一现象。 观察常规用于 NMR 实验 (3·20 Tesla) 的磁场中的 DNP 效应需要在相应的高场/高频 ESR 范围：90 600 GHz 下对样品进行微波辐射。 ACERT 具有在广泛频率范围内进行 ESR 实验的独特能力。 McDermott 教授（哥伦比亚大学）对 DNP 的兴趣主要集中在带有自由基的膜蛋白上。最近发现，具有相对短的自旋距离（d 10¿）的氮氧双自由基是非常有效的偏振剂。此外，已经表明，刚性双自由基比具有柔性系链的双自由基甚至是更强大的偏振剂。然而，关于双自由基及其如何在 DNP 中发挥作用，人们还没有充分了解。特别是，多自由基增强 DNP 弛豫的确切机制仍不清楚。 对现有和未来 DNP 极化剂在高频下 ESR 弛豫的详细研究将为 DNP 现象提供有价值的见解。为了从嵌入膜疏水核心的顺磁性核获得 DNP 增强的 NMR 信号，极化剂应该能够接近核。 ESR 光谱，特别是高场 ESR 光谱，可以轻松确定膜中可能的偏振剂的深度位置，并预测各种跨膜蛋白片段的可及性。