Britt R D, Peloquin J M, Campbell K A
Department of Chemistry, University of California, Davis 95616, USA.
Annu Rev Biophys Biomol Struct. 2000;29:463-95. doi: 10.1146/annurev.biophys.29.1.463.
Photosystem II uses visible light to drive the oxidation of water, resulting in bioactivated electrons and protons, with the production of molecular oxygen as a byproduct. This water-splitting reaction is carried out by a manganese cluster/tyrosine radial ensemble, the oxygen -evolving complex. Although conventional continuous-wave, perpendicular -polarization electron paramagnetic resonance (EPR) spectroscopy has significantly advanced our knowledge of the structure and function of the oxygen-evolving complex, significant additional information can be obtained with the application of additional EPR methodologies. Specifically, parallel-polarization EPR spectroscopy can be use to obtain highly resolved EPR spectra of integer spin Mn species, and pulsed EPR spectroscopy with electron spin echo-based sequences, such as electron spin echo envelope modulation and electron spin echo-electron nuclear double resonance, can be used to measure weak interactions obscured in continuous-wave spectroscopy by inhomogeneous broadening.
光系统II利用可见光驱动水的氧化，产生生物活化的电子和质子，并产生分子氧作为副产物。这种水分解反应是由锰簇/酪氨酸自由基集合体（即放氧复合体）进行的。尽管传统的连续波、垂直极化电子顺磁共振（EPR）光谱学极大地推进了我们对放氧复合体结构和功能的认识，但应用其他EPR方法可以获得大量额外信息。具体而言，平行极化EPR光谱学可用于获得整数自旋锰物种的高分辨率EPR光谱，而基于电子自旋回波序列的脉冲EPR光谱学，如电子自旋回波包络调制和电子自旋回波-电子核双共振，可用于测量连续波光谱中因不均匀展宽而被掩盖的弱相互作用。
