Enhanced Sensitivity Biological EPR

加雷斯·R·伊顿丹佛大学增敏生物电子顺磁共振(EPR)是一种研究未成对电子的光谱方法。未成对的电子经常出现在自然产生的蛋白质中，这些蛋白质在化学和生物学中很重要。未成对的电子也是由辐射损伤和食品和其他材料中的热解产生的。现代EPR方法可以确定未成对电子的详细环境、它们的寿命和它们的相互作用。例如，离散的自由基对之间的相互作用可以用来测量蛋白质中的距离。EPR为生物表征提供了独特的能力，其特点是：(1)该方法仅检测到未成对的电子，因此可以真正看到大海捞针；(2)EPR可以在固体或液体中看到未成对的电子，并在广泛的温度范围内；以及(3)大的电子磁偶极对EPR线形和驰豫时间产生非常长的影响。在膜中甚至整个细胞和组织中都可以观察到蛋白质的EPR谱，这种环境可能会混淆其他物理方法。不幸的是，由于严重的信噪比问题，EPR的这些优势有时不能在生物系统中得到利用。该奖项将支持EPR所能达到的信噪比水平的提高。该奖项将使将新发明的EPR谐振器、低温可冷却限制器和低噪声低温可冷却微波放大器组合到特定应用模块中成为可能。由此产生的光谱仪将用于研究其EPR信号太弱而无法用现有的商业EPR光谱仪进行有效研究的蛋白质。开发的技术将可转让，并可用于升级其他实验室的现有EPR光谱仪。丹佛大学的学生和游客将接受这项新技术的培训。通过与许多其他学校的研究人员合作，这项新技术将被应用于各种生物学问题，并将进行迭代改进，以尽可能为生物样本提供最佳的信噪比。

ABSTRACT9986942Gareth R. EatonUniversity of DenverEnhanced Sensitivity Biological EPRElectron paramagnetic resonance (EPR) is a spectroscopic method for studying unpaired electrons. Unpaired electrons are often found in naturally occurring proteins that are important in chemistry and biology. Unpaired electrons are also produced by radiation damage and by pyrolysis in foodstuffs and in other materials. Modern EPR methods can determine the detailed environment of unpaired electrons, their lifetimes, and their interactions. For example, interactions between discrete pairs of free radicals can be used to measure distances in proteins.The special features of EPR that provide unique power for biological characterization are that (1) the method detects only unpaired electrons, and thus can literally see the needle in the haystack; (2) EPR can see unpaired electrons in solids or in liquid solution phase and over a wide range of temperatures; and (3) the large electron magnetic dipole results in very-long-range effects on EPR line shapes and relaxation times. EPR spectra can be observed for proteins in membranes and even in whole cells and tissues, environments that can confound other physical methods. Unfortunately, these advantages of EPR sometimes cannot be exploited in biological systems because of a severe signal-to-noise problem. This award will support improvement in the signal-to-noise level attainable by EPR. The award will make it possible to combine newly invented types of EPR resonators, cryogenically coolable limiters, and low noise cryogenically coolable microwave amplifiers into application-specific modules. The resulting spectrometer will be used to study proteins whose EPR signals are too weak to be effectively studied by current commercial EPR spectrometers. The technology developed will be transferable and could be used to upgrade existing EPR spectrometers in other laboratories. Students, and visitors to the University of Denver, will be trained in the new technology. Through collaborations with researchers at many other schools the new technology will be applied to a wide variety of biological problems and will be iteratively refined to give the best signal-to-noise possible for biological samples.