Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK.
J R Soc Interface. 2010 Apr 6;7 Suppl 2(Suppl 2):S257-64. doi: 10.1098/rsif.2009.0399.focus. Epub 2009 Dec 9.
A critical requirement in the proposed chemical model of the avian magnetic compass is that the molecules that play host to the magnetically sensitive radical pair intermediates must be immobilized and rotationally ordered within receptor cells. Rotational disorder would cause the anisotropic responses of differently oriented radical pairs within the same cell to interfere destructively, while rapid molecular rotation would tend to average the crucial anisotropic magnetic interactions and induce electron spin relaxation, reducing the sensitivity to the direction of the geomagnetic field. So far, experimental studies have been able to shed little light on the required degree of ordering and immobilization. To address this question, computer simulations have been performed on a collection of radical pairs undergoing restricted rigid-body rotation, coherent anisotropic spin evolution, electron spin relaxation and spin-selective recombination reactions. It is shown that the ordering and motional constraints necessary for efficient magnetoreception can be simultaneously satisfied if the radical pairs are uniaxially ordered with a moderate order parameter and if their motional correlation time is longer than about a quarter of their lifetime.
在鸟类磁场罗盘的拟议化学模型中，一个关键要求是，充当磁敏自由基对中间体宿主的分子必须在受体细胞内固定和旋转有序。旋转无序会导致同一细胞内不同取向的自由基对的各向异性响应产生破坏性干扰，而快速分子旋转则会倾向于平均关键各向异性磁相互作用并诱导电子自旋弛豫，从而降低对地磁场方向的敏感性。到目前为止，实验研究还未能阐明所需的有序化和固定化程度。为了解决这个问题，对一系列经历受限刚体旋转、相干各向异性自旋演化、电子自旋弛豫和自旋选择重组反应的自由基对进行了计算机模拟。结果表明，如果自由基对具有中等有序参数的单轴有序，并且其运动相关时间长于其寿命的约四分之一，则可以同时满足有效磁受体所需的有序化和运动约束。
