Probing a chemical compass: novel variants of low-frequency reaction yield detected magnetic resonance
Probing a chemical compass: novel variants of low-frequency reaction yield detected magnetic resonance
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DOI：
10.1039/c4cp04095c
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发表时间：
2015-01-01
影响因子：
3.3
通讯作者：
Timmel, Christiane R.
中科院分区：
文献类型：
--
作者：
Maeda, Kiminori;Storey, Jonathan G.;Timmel, Christiane R.
我们提出了一个类胡萝卜素卟啉富勒烯三元组的研究以前显示作为一个化学罗盘：光生类胡萝卜素富勒烯自由基对重组率敏感的方向施加磁场。为了表征该系统，我们开发了一种时间分辨低频反应产率检测磁共振（TR-LF-RYDMR）技术;改变施加的静态和36 MHz振荡磁场的相对取向的效果被证明是强烈依赖于振荡磁场的强度。RYDMR是一种用于诊断反应速率或产量的磁场敏感性中自由基对机制参与的诊断测试，并且先前已应用于动物行为实验中，以验证基于自由基对的中间体参与候鸟的磁罗盘感。RYDMR的光谱选择规则在微波频率下被很好地理解，所谓的“高场近似”是有效的，但在较低的频率下需要不同的模型。例如，最近研究了旋转坐标系近似的分解，但迄今为止对取向效应的关注较少。在这里，我们获得的物理见解不同的磁相互作用的相互作用，影响低频RYDMR实验中进行的具有挑战性的制度，其中静态和振荡施加的磁场以及内部的电子-核超精细相互作用是相当的幅度。我们的观察有助于解释现有的RYDMR为基础的动物行为研究，并将告知未来的应用程序的技术，以进一步验证和表征生物受体参与鸟类磁感受。
We present a study of a carotenoid-porphyrin-fullerene triad previously shown to function as a chemical compass: the photogenerated carotenoid-fullerene radical pair recombines at a rate sensitive to the orientation of an applied magnetic field. To characterize the system we develop a time-resolved Low-Frequency Reaction Yield Detected Magnetic Resonance (tr-LF-RYDMR) technique; the effect of varying the relative orientation of applied static and 36 MHz oscillating magnetic fields is shown to be strongly dependent on the strength of the oscillating magnetic field. RYDMR is a diagnostic test for involvement of the radical pair mechanism in the magnetic field sensitivity of reaction rates or yields, and has previously been applied in animal behavioural experiments to verify the involvement of radical-pair-based intermediates in the magnetic compass sense of migratory birds. The spectroscopic selection rules governing RYDMR are well understood at microwave frequencies for which the so-called 'high-field approximation' is valid, but at lower frequencies different models are required. For example, the breakdown of the rotating frame approximation has recently been investigated, but less attention has so far been given to orientation effects. Here we gain physical insights into the interplay of the different magnetic interactions affecting low-frequency RYDMR experiments performed in the challenging regime in which static and oscillating applied magnetic fields as well as internal electron-nuclear hyperfine interactions are of comparable magnitude. Our observations aid the interpretation of existing RYDMR-based animal behavioural studies and will inform future applications of the technique to verify and characterize further the biological receptors involved in avian magnetoreception.