HIGH FIELD DNP AND EPR IN BIOLOGICAL SYSTEMS

描述：该提案概述了蛋白质和模型的研究 三种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CW 蛋白质的DNP/MAS光谱最近被观察到。 实验 将被用来增强信号强度在MAS NMR光谱的大 蛋白质类T4溶菌酶、细菌视紫红质和核糖核苷酸还原酶 (RNR)--含有外源性和内源性顺磁中心，如 克里思和酪氨酰基自由基。 实验使用140 GHz 回旋振荡器作为微波源，和首席研究员 将开发一种低温氦气再循环系统， DNP/MAS探针。 信号增强CA。 已经观察到100个， 导致采集时间减少10，000倍。 (2)脉冲 计划进行基于哈特曼-哈恩交叉极化的DNP实验， 单晶样品以及粉末。 (3)140 GHz CW EPR ENDOR 计划对五种不同的系统进行调查： 核糖核苷酸还原酶（RNR）的抑制剂;（B）形成的X-中间体 结合Fe和apoRNR;（c）与 腺苷钴胺素;（d）丙酮酸甲酸裂解酶中的甘氨酰自由基;（e） 在光系统-II中酪氨酰自由基的研究（4）140 GHz脉冲EPR实验将 可用于研究频率、浓度和温度依赖性， DNP模型系统中电子自旋晶格弛豫（T1 e） 实验和蛋白质。 这些数据对于优化速率是有用的 和偏振增强的幅度来确定 含有自由基和顺磁中心的蛋白质， 天生有趣

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.