TRANSIENT MAGNETIC CIRCULAR DICHROISM

一项新技术将被开发出来， 磁圆二色性测量的分辨率 从毫秒时间制度，标准技术可以 解决，到纳秒时间制度。 MCD将在 激光光解样品的应用强磁场 磁场（100 kgauss），并使用最近演示的 在纳秒上测量圆二色性的方法 时间尺度 瞬态MCD技术具有广泛的 潜在的应用，因为MCD可以在任何光- 通过足够强的磁场吸收样品。 这是 与需要手性样品的CD相反， 二向色性，这需要定向的样品。 有效 高时间分辨率MCD信号测量技术 将是生物物理学的一个重要工具，因为它将提供 结构MCD研究和动力学研究之间的联系。 以来 生物过程依赖于生物的结构特性 分子和动态的性质，这种联系显然是 巨大的潜在效用。 这项研究的目标是 开发和评估瞬态MCD的有用性 技术作为生物物理研究的工具。 该方法的初步应用将在激发态 自由基卟啉。 它们强烈的，被充分研究的基态 MCD，合适的激发态寿命，和光谱的缺乏， 基态和激发态选择之间的重叠提供了 检测瞬态MCD的优良条件。 瞬态 对于铜的激发态也将得到MCD谱 卟啉和钌双卟啉。 此外，MCD 光谱将获得基态瞬态产生的 7-羟基黄酮的光互变异构， 在碱性溶剂中从镍四苯基卟啉得到轴向配体， 以及碳一氧肌红蛋白的光解。 最后 细胞色素蛋白质的瞬时MCD已被“脉冲- 通过光解获得的溶剂化电子“还原” 将研究亚铁氰化物。

A new technique will be developed which extends the time resolution of magnetic circular dichroism (MCD) measurements from the millisecond time regime, which standard techniques can resolve, to the nanosecond time regime. MCD will be induced in a laser-photolysed sample by application of a strong magnetic field (100 kgauss) and measured with a recently demonstrated method of measuring circular dichroism (CD) on a nanosecond time scale. The transient MCD technique has a wide range of potential applications since MCD can be induced in any light- absorbing sample by a sufficiently strong magnetic field. This is in contrast to CD, which requires a chiral sample, and linear dichroism, which requires an oriented sample. An effective technique for measuring MCD signals with high time resolution would be an important tool for biophysics since it would provide a link between structural MCD studies and kinetic studies. Since biological processes depend on structural properties of biological molecules and are dynamic in nature, this linkage is clearly of great potential utility. The goal of this research will be to develop and assess the usefulness of the transient MCD technique as a tool for biophysical studies. Initial application of the method will be made to excited states of free-base porphyrins. Their intense, well-studied ground state MCD, suitable excited state lifetimes, and the lack of spectral overlap between ground and excited state absorptions provide excellent conditions for detecting transient MCD. Transient MCD spectra will also be obtained for excited states of copper porphyrins and Ruthenium biporphyrins. In addition, MCD spectra will be obtained for ground state transients generated by phototautomerization of 7-hydroxyflavone, photodissociation of axial ligands from nickel tetraphenylporphyrin in basic solvents, and the photolysis of carbonmonoxymyoglobin. Finally, the transient MCD of cytochrome proteins that have been "pulse- reduced" by solvated electrons obtained by photolysis of ferrocyanide will be studied.