HIGH FIELD DNP AND EPR IN BIOLOGICAL SYSTEMS

描述：该提案概述了对蛋白质和模型的研究 采用三大创新磁共振技术的系统：高频 动态核极化(DNP)，140 GHz电子顺磁共振 (EPR)和电子核双共振(Endor)。(1)高频连续波 最近观察到一种蛋白质的DNP/MAS光谱。这些实验 将被用来增强MAS核磁共振谱中的信号强度 蛋白质--T4溶菌酶、细菌视紫红质和核苷酸还原酶 (RnR)--包含外源和内源顺磁中心，如 分别是Tempo和Tyrosyl自由基。这些实验使用了140 GHz 作为微波源的Gyotron振荡器，以及首席研究员 将开发一种低温氦再循环系统，用于 DNP/MAS探头。已经观察到约100的信号增强， 从而使获取时间减少了10,000倍。(2)脉冲 基于Hartman-Hahn交叉极化的DNP实验计划用于 单晶样品和粉末。(3)140 GHz连续波EPR端子 计划对五种不同的系统进行调查：(A)氟化系统 核糖核苷酸还原酶(RNR)抑制剂；(B)形成的X-中间体 铁与apoRNR结合的研究；(C)与 腺苷钴胺；(D)丙酮酸甲酸裂解酶中的甘氨酸基；(E) 光系统中的酪氨酸自由基-II(4)140 GHz脉冲EPR实验将 被用来研究频率、浓度和温度的依赖关系 DNP模型体系中的电子自旋晶格驰豫(T1e) 实验和蛋白质中。这些数据对于优化速率是有用的 和极化增强的大小来确定结构 含有自由基和顺磁中心的蛋白质， 从本质上讲很有趣。

DESCRIPTION: This proposal outlines investigations of proteins and model systems with three innovation magnetic resonance techniques: high frequency dynamic nuclear polarization (DNP), 140 GHz electron paramagnetic resonance (EPR), and electron nuclear double resonance (ENDOR). (1) High frequency CW DNP/MAS spectra of a protein have recently been observed. The experiments will be employed to enhance signal strengths in MAS NMR spectra of large proteins -- T4 lysozyme, bacteriorhodopsin, and ribonucleotide reductase (RNR) -- containing exogenous and endogenous paramagnetic centers such as TEMPO and tyrosyl radicals, respectively. The experiments utilize a 140 GHz gryotron oscillator as a microwave source, and the principal investigator will develop a low temperature helium recirculating system for use with DNP/MAS probes. Signal enhancements of ca. 100 have been observed, resulting in a factors of 10,000 decrease in acquisition time. (2) Pulsed DNP experiments based on Hartman-Hahn cross polarization are planned for single crystals samples as well as powders. (3) 140 GHz CW EPR ENDOR investigations are planned for five different systems: (a) a fluorinated inhibitor of ribonucleotide reductase (RNR); (b) the X-intermediate formed on combining Fe and the apoRNR; (c) thiyl radicals associated with adenosylcobalamin; (d) glycyl radicals in pyruvate formate lyase; (e) tyrosyl radicals in photosystem-II (4) 140 GHz pulsed EPR experiments will be used to study the frequency, concentration and temperature dependence of the electron spin lattice relaxation (T1e) in model systems for DNP experiments and in proteins. The data are useful for optimizing the rate and magnitude of polarization enhancements in determining structures of proteins containing free radicals and paramagnetic centers, and are inherently interesting.