Construction of a Variable Frequency Ka Band [26-40 GHz] Pulsed EPR Spectrometer for Multi-Dimensional ESEEM and ENDOR Studies of Metalloproteins

该合同支持开发可变频率脉冲ka波段（26-40 GHz） EPR光谱仪，用于电子自旋回波包络调制（ESEEM）和电子-核双/三共振（ENDOR/ENQOR）研究含有顺磁性金属原子的蛋白质。生物分子中的顺磁性金属中心是非常敏感的“信标”，其与附近磁性原子核的磁耦合揭示了金属原子的直接环境，从而可以提供催化反应途径的详细信息。O、N或S原子配体在许多生物分子的顺磁性金属中心中起着至关重要的作用。要开发的硬件和软件将使强大的多维脉冲EPR方法扩展到附近的磁性核，如17O和33S的研究。此外，该仪器将大大简化与14N原子耦合的分析。这些原子的超精细相互作用（hfi）和核四极子（nqi）参数将为它们的顺聚金属中心提供直接的认识。该项目包括仪器的建设、数据采集、数据处理和光谱模拟软件的开发。这种新型脉冲EPR谱仪系统的初步应用将是钼酶和铁血红素电子转移蛋白的催化过程。然而，这种先进的脉冲EPR仪器将是一个强大的工具，它将使生物化学家、生物物理学家和生物无机化学家能够以前所未有的细节绘制出生物系统中顺磁性金属中心的周围环境。一旦该仪器完全投入使用，预计将进行大量的国家和国际合作研究，并且在这个项目中开发的软件将普遍提供给科学界。

This award supports the development of a variable frequency pulsed Ka-band (26-40 GHz) EPR spectrometer for electron spin echo envelope modulation (ESEEM) and electron-nuclear double/triple resonance (ENDOR/ENQOR) studies of proteins containing paramagnetic metal atoms. Paramagnetic metal centers in biomolecules are exquisitely sensitive "beacons", whose magnetic coupling to nearby magnetic nuclei reveal the immediate surroundings of the metal atom and can thereby provide detailed information about catalytic reaction pathways. Ligands with coordinated O, N, or S atoms play crucial roles in the paramagnetic metal centers of many biomolecules. The hardware and software to be developed will enable powerful multi-dimensional pulsed EPR methods to be extended to the investigation of nearby magnetic nuclei such as 17O and 33S. In addition, this new instrument will substantially simplify the analysis of coupling with 14N atoms. The hyperfine interaction (hfi) and nuclear quadrupole (nqi) parameters obtained for these atoms will provide direct insight into their paramagetic metal centers. The project includes construction of the instrument, and development of software for data acquisition, data processing and spectral simulation. The initial applications of this new pulsed EPR spectrometer system will be to the catalytic processes of molybdenum enzymes and ferriheme electron-transfer proteins. However, this advanced pulsed EPR instrument will be a powerful tool that will enable the surroundings of paramagnetic metal centers in biological systems to be mapped out in unprecedented detail by biochemists, biophysicists and bioinorganic chemists. A large number of national and international collaborative studies are envisioned once the instrument becomes fully operational, and the software developed in this project will be made generally available to the scientific community.