HIGH FREQUENCY ELECTRON ELECTRON DOUBLE RESONANCE SPECTROSCOPY

高频电子电子双共振能谱

• 批准号: 6279716
• 负责人: DENNIS A HALL
• 金额: $ 2.13万
• 依托单位: MASSACHUSETTS INSTITUTE OF TECHNOLOGY
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-05-01 至 1999-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6279716
• 关键词: biological products; biomedical equipment development; biomedical resource; technology /technique

ELDOR is a magnetic resonance technique which is used to determine motional dynamics, relaxation properties, and molecular structure in paramagnetie systems. The technique requires the irradiation of a sample at two distinct EPR (Electron Paramagnetic Resonance) spectral positions. In the experiment described here, this is accomplished by irradiation with two different microwave frequencies from two distinct sources. A saturating (pump) pulse at 139.6S GHz is applied to the sample for 1 1.tsec to 10 msec. The effect of this pulse at a different spectral position (150 MHz upfield) is then monitored using a spin echo detection (probe) sequence at 139.50 GHz. The detection pulses are typically 300-600 ns in duration. Three switches are used in the ELDOR experimental set-up: one to form the saturating (pump) pulse. one to switch the low power detection (probe) pulses, and one to protect the mixer from high power. The switches provided by Capital Technology Corporation (CTC) have been used successfully to gate the high frequency (139.65 GHz) saturating pulse produced by the gyrotron. For various reasons, relatively low power saturation pulses have been used to date. However, it is desirable to use as much power as can be provided by the microwave source. These CTC switches are the only ones currently manufactured which have the insertion loss, power-handling capability, and switching times required for a high power (10 W) ELDOR experiment. Further improvements in CTC switch rise/fall times will allow their use to form the detection pulses. This will allow higher powers to be used in the detection pulse sequence, improving the signal-to-noise ratio and increasing the available detection bandwidth. ELDOR experiments have been performed on frozen solution samples of 4-amino TEMPO in 60:40 glycerol/water at 10 K. For a 4-amino TEMPO concentration of 40 mM, clear evidence of spectral diffusion is observed; the probe electron spin echo is attenuated due to the pump pulse. This attenuation is maximal when the pump pulse irradiates at the first moment of the EPR line. No such attenuation of the probe electron spin echo is observed for 1 mM 4-amino TEMPO. These results indicate a significant dipolar coupling between unpaired electrons in the 40 mM sample. This dipolar coupling facilitates electron-electron cross-relaxation, which can be exploited via dynamic nuclear polarization (DNP) to increase of signal-to-noise ratios of solid state nuclear magnetic resonance (NMR).

Eldor是一种磁共振技术，用于确定 分子的运动动力学、弛豫特性和分子结构 顺磁系统。这项技术需要照射一种 两种不同EPR谱下的样品 各就各位。在这里描述的实验中，这是通过以下方式完成的 两种不同频率的两种不同微波辐射 消息来源。139.6S GHz的饱和(泵浦)脉冲被施加到 采样时间为11.1tsec到10msec。这一脉冲的影响在一个 不同的频谱位置(150 MHz前场)然后使用 139.50 GHz的自旋回波探测(探测)序列。该检测 脉冲的持续时间通常为300-600 ns。使用了三个开关 在Eldor实验装置中：一个形成饱和(泵)的装置 脉搏。一个用于切换低功率检测(探测)脉冲，以及一个 以保护搅拌器不受高功率影响。由提供的开关 Capital Technology Corporation(CTC)已成功用于 选通由产生的高频(139.65 GHz)饱和脉冲 回旋管。由于各种原因，相对较低的功率饱和脉冲 到目前为止已经被使用了。然而，希望使用尽可能多的功率 如微波源所能提供的。这些CTC交换机是 目前制造的唯一具有插入损耗的， 功率处理能力和开关时间要求高 功率(10W)Eldor实验。CTC交换机的进一步改进 上升/下降时间将允许使用它们来形成检测脉冲。 这将允许在检测脉冲中使用更高的功率 序列，提高了信噪比，提高了图像质量 可用检测带宽。已经进行了Eldor实验 4-氨基TEMPO在60：40甘油/水中的冷冻溶液 10K，对于40 mM的4-氨基节奏浓度，明显的证据 观察到光谱扩散；探测电子自旋回波是 由于泵浦脉冲而衰减。这种衰减在以下情况下达到最大 泵浦脉冲在EPR线的第一个时刻照射。不是 探测器电子自旋回波的这种衰减可观察到1 mm 4-氨基节拍。这些结果表明存在显著的偶极耦合。 在40 mm样品中未配对的电子之间。这种偶极耦合 促进电子-电子的交叉弛豫，这是可以利用的 通过动态核极化(DNP)提高信噪比 固体核磁共振的比率。