High Field and Multi-Frequency EPR in Single Crystals of Sperm Whale Met-Myoglobin : Determination of the Axial Zero-Field Splitting Constant and Frequency Dependence of the Linewidth(Cross-disciplinary Physics and Related Areas of Science and Technology)

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Electron paramagnetic resonance (EPR) measurements for frequencies from 28.5 GHz to 608.1 GHz and magnetic field up to 14T have been performed on single crystals of sperm whale high-spin (S = 5/2) met-myoglobin. The EPR resonance field along the c^*-axis deviates from the g = 5.71 straight line at high frequencies. The axial zero-field splitting constant (D) of the met-myoglobin sample is evaluated to be 9.47 ± 0.05 cm^<-1> by analyzing the resonance fields with the S = 5/2 spin Hamiltonian including the D term. The angular dependence of EPR spectra in the ab plane has been also investigated at high frequencies. Two kinds of EPR spectra are observed corresponding to two kinds of different heme sites in the unit cell. A notable change in the linewidth of the spectrum along the c^*-axis occurs above 350GHz, suggesting that the dominant relaxation process changes around 350GHz. The origins of the linewidth arediscussed.
社団法人日本物理学会の論文
2004-01-15