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Development of a New Two-dimensional Pulsed EPR Method and an Application to Heme-proteins

新型二维脉冲 EPR 方法的开发及其在血红素蛋白中的应用

基本信息

批准号：
11640495
负责人：
OHBA Yasunori
金额：
$ 2.05万
依托单位：
Institute for Chemical Reaction Science, Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11640495/
关键词：
electron paramagnetic resonance electron spin resonance nutation spectrum heme protein myoblobin pulsed EPR 電子常時性共鳴

项目摘要

A new technique of two-dimensional nutation spectroscopy for a disordered system with large g-anisotropy was developed. This method is based on the fact that a nutational frequency is determined by the g value which belongs to the direction perpendicular to the external magnetic field. The method enables one to determine a very small g-value (typically less than 1) and relative sign of g-principal values. The method is applied to low-spin met myoglobin from horse heart.1. The most important part of the pulsed EPR instrument for the nutational experiment is the microwave resonator. A strong and homogeneous microwave field is essential. A loop-gap resonator was compared with a rectangular cavity resonator. A stable sample holder of a loop-gap resonator for helium temperature measurements was designed and constructed.2. A nutation signal from a disordered sample was analyzed by a spectral simulation technique. A gated integration and ESE-FT methods were compared as a detection technique. The analysis showed that there was some distortion and shift of a spectrum in a gated integration caused by off-resonance effects. These artifacts could be removed by the ESE-FT technique.3. Two-dimensional nutation spectra were observed for low-spin horse heart met-myoglobin in frozen solution. By means of the ESE-FT technique, the nutation spectra those were free from off-resonance effects were obtained. The spectra were compared with theoretical predictions for magnetic field dependence of a nutational spectrum. It is confirmed that a nutation frequency was determined by the g-principal value of the direction orthogonal to the external magnetic field. The very small g-value of cyanide ion complex, g=0.93, could be observed by this method.4. It was predicted by the theoretical analysis that relative sign of g-principal values could be determined by a nutation spectrum from a disordered system.

提出了一种用于大g各向异性无序体系的二维章动光谱新技术。这种方法是基于一个事实，即一个国家的频率是由属于垂直于外磁场方向的g值决定的。该方法使人们能够确定一个非常小的g值（通常小于1）和g主值的相对符号。该方法适用于马心脏低旋肌红蛋白。国家实验用脉冲EPR仪器中最重要的部分是微波谐振腔。强而均匀的微波场是必不可少的。对环隙谐振器与矩形腔谐振器进行了比较。设计并制造了一种用于氦温度测量的环隙谐振器的稳定样品架。用谱模拟技术对无序样品的章动信号进行了分析。比较了门控积分和ESE-FT两种检测方法。分析表明，由于非共振效应，门控积分中存在一定的频谱畸变和偏移。这些伪影可以通过ESE-FT技术去除。在冷冻溶液中观察了低自旋马心脏-肌红蛋白的二维章动光谱。利用ESE-FT技术，得到了不受非共振效应影响的章动谱。将所得光谱与国家光谱磁场依赖性的理论预测结果进行了比较。证实了章动频率是由与外磁场正交方向的g主值决定的。用这种方法可以观察到氰化物离子络合物的g值很小，g=0.93。通过理论分析预测，可以用无序系统的章动谱确定g主值的相对符号。