Interaction of Spin Labels with Transition Metals

自旋标记与过渡金属的相互作用

• 批准号: 6875840
• 负责人: Gareth R Eaton
• 金额: $ 50.2万
• 依托单位: UNIVERSITY OF DENVER (COLORADO SEMINARY)
• 依托单位国家: 美国
• 财政年份: 1977
• 资助国家: 美国
• 起止时间: 1977-07-01 至 2008-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6875840
• 关键词: bacterial proteins; bioengineering /biomedical engineering; biophysics; chemical models; chemical structure; dipole moment; electron spin resonance spectroscopy; electron transport; free radicals; heavy metals; heme; intermolecular interaction; iron; magnetism; membrane channels; method development; molecular dynamics; myoglobin; nitrogen oxides; oxidoreductase; receptor; relaxation spectrometry; siderophores; structural biology; temperature

DESCRIPTION (provided by applicant): The goal of the proposed research is to develop, validate, and apply electron paramagnetic resonance (EPR) methodology for measuring distances in non-crystalline biological systems. The unique power of EPR among the many techniques for measuring distances is that the paramagnetic centers may be native or added via site-directed mutagenesis, the electron spin dipole moment is large enough to yield long-range interactions, and EPR is sensitive only to the paramagnetic centers, even deeply buried in vast numbers of nuclear spins or light-absorbing species. The distance information is in the dipolar interaction between electron spins, which can be measured by continuous wave (CW) or pulsed EPR techniques. This proposal emphasizes X-band and Q-band pulse techniques because they measure the impact of spin-spin interaction on spin packets directly, rather than requiring interpretation of broadened CW spectra. Q-band offers enhanced sensitivity, spectral dispersion, and orientation selection. In the current funding period we developed saturation recovery and spin echo methods for measuring distances between rapidly-relaxing heme Fe(III) and a nitroxyl radical. In the proposed funding period we will address unanswered questions related to these techniques and extend them to other iron centers - the iron-sulfur cluster in electron transfer flavoprotein ubiquinone oxidoreductase (ETF-QO) and the non-heme iron in iron enterobactin (FeEnt) bound to iron protein A (FepA). These systems provide the opportunity to examine the effect of electron spin delocalization (ETF-QO) on the distance measurements and the effect of iron energy level splittings comparable to the EPR quantum (FepA). Pulsed double electron-electron resonance (DEER) is a complementary method to measure distances between two slowly relaxing paramagnetic centers, and we propose to enhance its utility for biological samples. Two inter-related themes extend across the three specific aims - orientation selection and conformational flexibility. The methods that we develop will permit us to address important biological questions raised by our collaborators. We will determine the conformational change in the tonB box of iron protein A, characterize structure changes in the redox active sites of electron transfer flavoprotein ubiquinone reductase, and elucidate the mechanism of DNA melting by large tumor antigen.

描述（由申请人提供）：拟议研究的目标是开发、验证和应用电子顺磁共振（EPR）方法测量非晶体生物系统中的距离。在众多测量距离的技术中，EPR的独特能力在于顺磁中心可以是天然的或通过定点诱变添加的，电子自旋偶极矩足够大以产生长程相互作用，并且EPR仅对顺磁中心敏感，甚至深埋在大量的核自旋或光吸收物质中。距离信息存在于电子自旋之间的偶极相互作用中，其可以通过连续波（CW）或脉冲EPR技术来测量。该建议强调X波段和Q波段脉冲技术，因为它们直接测量自旋-自旋相互作用对自旋包的影响，而不需要解释加宽的CW光谱。Q波段提供增强的灵敏度、光谱色散和方向选择。 在当前的资助期内，我们开发了饱和恢复和自旋回波方法，用于测量快速弛豫的血红素Fe（III）和硝酰基自由基之间的距离。在拟议的资助期间，我们将解决与这些技术相关的未回答的问题，并将其扩展到其他铁中心-电子转移黄素蛋白泛醌氧化还原酶（ETF-QO）中的铁硫簇和铁肠杆菌素（FeEnt）中的非血红素铁与铁蛋白A（FepA）结合。这些系统提供了机会，检查电子自旋离域（ETF-QO）的距离测量和铁的能级分裂的效果与EPR量子（FepA）的影响。脉冲双电子-电子共振（DEER）是一种测量两个缓慢弛豫的顺磁中心之间距离的补充方法，我们建议提高其对生物样品的实用性。两个相互关联的主题延伸到三个具体的目标-取向选择和构象灵活性。我们开发的方法将使我们能够解决合作者提出的重要生物学问题。我们将确定铁蛋白A的tonB盒的构象变化，表征电子转移黄素蛋白泛醌还原酶的氧化还原活性位点的结构变化，并阐明大肿瘤抗原的DNA熔化机制。