Antholine W E, Hanna P M, McMillin D R
National Biomedical ESR Center, Biophysics Research Institute, Medical College of Wisconsin, Milwaukee 53226.
Biophys J. 1993 Jan;64(1):267-72. doi: 10.1016/S0006-3495(93)81363-8.
The type 1 copper in Pseudomonas aeruginosa azurin was studied by electron paramagnetic resonance (EPR) spectroscopy at low microwave frequencies. Partially resolved ligand hyperfine structure was observed in the perpendicular region of the spectra at both S-band (2.4 GHz) and L-band (1.1 GHz). A trial and error method, requiring several hundred simulations, has been used to simulate the low frequency EPR data and yield an optimum value of 30 MHz for ACUx, more than one half that previously reported. The fit between the simulated and experimental data is sensitive to changes in the Euler angles and, in particular, to the angle alpha which rotates the Cu A-tensor about the z-axis. Thus, the A- and g-tensors for copper in P. aeruginosa azurin do not appear to be coincident. A value for the Euler angle beta of at least 10 degrees does not disturb the fit between the simulated and experimental data. These studies demonstrate the advantage of evaluating EPR parameters from simulations at more than one frequency, especially at low frequencies where ligand superhyperfine structure may be resolved for type 1 copper.
利用电子顺磁共振（EPR）光谱在低微波频率下研究了铜绿假单胞菌天青蛋白中的1型铜。在S波段（2.4 GHz）和L波段（1.1 GHz）的光谱垂直区域均观察到部分分辨的配体超精细结构。采用一种需要数百次模拟的试错法来模拟低频EPR数据，并得出ACUx的最佳值为30 MHz，这比之前报道的值的一半还多。模拟数据与实验数据之间的拟合对欧拉角的变化很敏感，特别是对使Cu A张量绕z轴旋转的α角很敏感。因此，铜绿假单胞菌天青蛋白中铜的A张量和g张量似乎不重合。欧拉角β至少为10度的值不会干扰模拟数据与实验数据之间的拟合。这些研究证明了在多个频率下，特别是在低频下评估EPR参数的优势，在低频下1型铜的配体超超精细结构可能会被分辨出来。
