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，以延长时间 磁圆二色性（MCD）测量的分辨率 从毫秒时期制度，标准技术可以 解决，到纳秒时间制度。 MCD将被诱导 通过使用强磁性的激光量载样品 田地（100 kgaus），并用最近证明的 测量纳秒上圆二色性（CD）的方法 时间尺度。 瞬态MCD技术具有广泛的 潜在的应用，因为可以在任何光中诱导MCD 通过足够强的磁场吸收样品。 这是 与需要手性样品和线性的CD相反 二分性能，需要取向样本。 有效 用高时间分辨率测量MCD信号的技术 将是生物物理学的重要工具，因为它将提供 结构MCD研究与动力学研究之间的联系。 自从 生物过程取决于生物学的结构特性 分子本质上是动态的，这种联系显然是 巨大的潜在效用。 这项研究的目的是 开发和评估瞬态MCD的实用性 技术作为生物物理研究的工具。 该方法的初始应用将用于激发状态 自由基卟啉。 他们强烈的，良好的基态 MCD，合适的激发态寿命，缺乏光谱 地面和激发状态吸收之间的重叠提供 检测瞬态MCD的良好条件。 瞬态 也将获得MCD光谱的铜 卟啉和双磷脂。 此外，MCD 将获得用于由 7-羟基氟氟酮的光态化，光解离 来自碱性溶剂中镍四苯基卟啉的轴向配体，碱性溶剂， 以及碳氨毒素蛋白的光解。 最后， 细胞色素蛋白的瞬态MCD是脉冲 - 通过光解获得的溶剂化电子降低 将研究苯氰化物。