TRANSIENT MAGNETIC CIRCULAR DICHROISM

瞬态磁性圆二色性

• 批准号: 3295063
• 负责人: DAVID S. KLIGER
• 金额: $ 13.01万
• 依托单位: UNIVERSITY OF CALIFORNIA SANTA CRUZ
• 依托单位国家: 美国
• 财政年份: 1987
• 资助国家: 美国
• 起止时间: 1987-07-01 至 1990-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3295063
• 关键词: circular magnetic dichroism; conformation; cytochrome oxidase; cytochromes; hemoglobin; magnetic field; myoglobin; photochemistry; photolysis; porphyrins; tautomer; triplet state

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.

将开发一种新技术来延长时间 磁圆二色性 (MCD) 测量的分辨率 从毫秒时间机制来看，标准技术可以 解决，到纳秒时间制度。 MCD 将在 通过应用强磁力激光光解样品 场（100 kgauss）并用最近证明的测量 纳秒测量圆二色性 (CD) 的方法 时间尺度。 瞬态 MCD 技术具有广泛的应用范围 潜在的应用，因为 MCD 可以在任何光下诱导 通过足够强的磁场吸收样品。 这是 与 CD 不同，CD 需要手性样本，而线性 二色性，需要定向样品。 一个有效的 高时间分辨率 MCD 信号测量技术 将成为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。 自从 生物过程取决于生物的结构特性 分子并且本质上是动态的，这种联系显然是 巨大的潜在效用。 这项研究的目标是 开发并评估瞬时 MCD 的有用性 技术作为生物物理学研究的工具。 该方法的最初应用将针对激发态 游离碱卟啉。 它们强烈的、经过充分研究的基态 MCD、合适的激发态寿命以及缺乏光谱 基态和激发态吸收之间的重叠提供 检测瞬态 MCD 的绝佳条件。 瞬态 还将获得铜的激发态的 MCD 光谱 卟啉和钌双卟啉。 此外，MCD 将获得由以下生成的基态瞬变的光谱 7-羟基黄酮的光互变异构，光解离 碱性溶剂中四苯基卟啉镍的轴向配体， 以及碳单氧肌红蛋白的光解作用。 最后， 细胞色素蛋白的瞬时 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。