Leu Bogdan M, Timothy Sage J, Zgierski Marek Z, Wyllie Graeme R A, Ellison Mary K, Robert Scheidt W, Sturhahn Wolfgang, Ercan Alp E, Durbin Stephen M
Steacie Institute for Molecular Science, National Research Council of Canada, Ottawa, Ontario, Canada K1A OR6.
J Phys Chem Solids. 2005 Dec;66(12):2250-2256. doi: 10.1016/j.jpcs.2005.09.075.
High-resolution X-ray measurements near a nuclear resonance reveal the complete vibrational spectrum of the probe nucleus. Because of this, nuclear resonance vibrational spectroscopy (NRVS) is a uniquely quantitative probe of the vibrational dynamics of reactive iron sites in proteins and other complex molecules. Our measurements of vibrational fundamentals have revealed both frequencies and amplitudes of (57)Fe vibrations in proteins and model compounds. Information on the direction of Fe motion has also been obtained from measurements on oriented single crystals, and provides an essential test of normal mode predictions. Here, we report the observation of weaker two-quantum vibrational excitations (overtones and combinations) for compounds that mimic the active site of heme proteins. The predicted intensities depend strongly on the direction of Fe motion. We compare the observed features with predictions based on the observed fundamentals, using information on the direction of Fe motion obtained either from DFT predictions or from single crystal measurements. Two-quantum excitations may become a useful tool to identify the directions of the Fe oscillations when single crystals are not available.
在核共振附近进行的高分辨率X射线测量揭示了探针原子核的完整振动光谱。因此，核共振振动光谱（NRVS）是蛋白质和其他复杂分子中活性铁位点振动动力学的独特定量探针。我们对振动基频的测量揭示了蛋白质和模型化合物中（57）Fe振动的频率和振幅。通过对取向单晶的测量也获得了有关Fe运动方向的信息，这为正常模式预测提供了重要检验。在此，我们报告了对模拟血红素蛋白质活性位点的化合物中较弱的双量子振动激发（泛音和组合）的观测。预测强度强烈依赖于Fe运动的方向。我们使用从DFT预测或单晶测量中获得的有关Fe运动方向的信息，将观测到的特征与基于观测到的基频的预测进行比较。当没有单晶时，双量子激发可能会成为识别Fe振荡方向的有用工具。
