ELECTRONIC SPECTROSCOPY OF SIMPLE PORPHYRINS AND BACTERIORHODOPSIN

简单卟啉和细菌视紫红质的电子光谱

• 批准号: 6107221
• 负责人: LAWRENCE William JOHNSON
• 金额: $ 20.71万
• 依托单位: YORK COLLEGE
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-06-01 至 2000-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6107221
• 关键词: alkanes; bacteriorhodopsins; chemical synthesis; chlorin; chromophore; dipole moment; electronic spectra; laser spectrometry; metal complex; metalloporphyrins; photochemistry; porphyrin structure

The research described in this proposal is a continuation, extention and modification of the work being carried out under our current MBRS grant. It is a study of simple porphyrins in the solid-state at 5K with respect to their electronic ground and excited state properties using single site excitation, optical hole-burning and the Stark effect. The fundamental hypothesis driving this research is that the excited states and the presence of low energy Npi* transitions. In this phase of our work both free base and metal complex forms of these molecules will be studied: e.g. porphin, chlorin, tetraazaporphin. These simple porphyrins are the parent compounds of biomedically important moieties (e.g. hemes, cytochromes, chlorophylls and photodynamic photosensitizers). Porphyrins are and have been actively studied, however most of the spectroscopic data sis from room temperature solutions which yield only broad bands. Our approach is to place the molecules in n-alkane host crystals; at liquid helium temperatures highly resolved (about 2 cm-1) spectra are obtained. The spectrum of molecules in a particular crystal environment can then be isolated by using single site-excitation. This high resolution can be improved even more by using optical hole-burning. When a molecule is dissolved in a matrix, its electronic spectrum is inhomogeneously broadened; when a narrow bandwidth laser is employed for excitation it is sometimes possible to burn holes in the inhomogeneously broadened bands; holes result from photochemistry, transient storage or molecular reorientation. When the narrow bands of single site spectra, or optical holes are coupled with the Stark effect, they provide a sensitive proble of molecular electronic states. Our overall methodology involves the growth of single mixed crystals (porphyrin/n-alkane) or making low temperature glassy solutions. The sample is immersed in liquid N2 or He and an absorption or emission spectrum obtained. Single site spectra are made or optical holes burned and scanned with a narrow band laser. For Stark effect experiments, a coniscopically oriented crystal is placed between electrodes. The electric field can be applied either DC or pulsed depending on the need. The primary long-term objective of this project is to use these techniques to extract detailed excited state information (e.g., vibrational energies, dipole moments, pi pi* and npi* origin energies, coupling, etc.) from these biomedically important chromophores. (Of particular interest now is that we seem to be finding strong evidence for the presence of low energy pi* lesser--- n transitions in some of these simple porphyrins). This research will involve two MBRS students. Each one will be responsible for a separate chromophore and will carry out its preparation, purification and run low and medium resolution spectra. Laser and Stark experiments will be done with the PI. Most of the spectroscopic data now available on these chromophores is low resolution because of substantial inhomogeneous broadening of the electronic bands. Optical hole-burning, single site excitation and the Stark effect will provide a clearer picture of the electronic states of these biomedically important molecules.

本提案中描述的研究是一种延续、延伸和 修改我们当前的 MBRS 赠款下正在进行的工作。 这是对 5K 固态简单卟啉的研究 使用单点的电子基态和激发态特性 激发、光学烧孔和斯塔克效应。 基本的 推动这项研究的假设是激发态和 存在低能量 Npi* 跃迁。 在我们这个阶段的工作中 将研究这些分子的游离碱和金属络合物形式：例如 卟啉、二氢卟酚、四氮杂卟啉。 这些简单的卟啉是母体 生物医学重要部分的化合物（例如血红素、细胞色素、 叶绿素和光动力光敏剂）。 卟啉是并且已经 已被积极研究，但是大多数光谱数据来自房间 只产生宽带的温度解决方案。 我们的方法是 将分子置于正烷烃主体晶体中；在液氦 获得高分辨率（约 2 cm-1）温度光谱。 这 特定晶体环境中的分子光谱可以是 通过使用单位点激发进行分离。 这个高分辨率可以 通过使用光学烧孔技术可以进一步改善。 当一个分子是 溶解在基体中，其电子能谱不均匀 扩大；当采用窄带宽激光器进行激发时，它是 有时可能会在不均匀加宽的带中烧孔； 空穴是由光化学、瞬时存储或分子产生的 重新定位。 当单点光谱或光学的窄带 空穴与斯塔克效应相结合，它们提供了一个敏感的问题 分子电子态。 我们的整体方法论涉及增长 单混合晶体（卟啉/正烷烃）或低温制备 玻璃状溶液。 将样品浸入液氮或氦气中 获得吸收或发射光谱。 制作单点光谱或 用窄带激光烧制和扫描光学孔。 为了斯塔克 效应实验中，将圆锥形取向的晶体放置在 电极。 电场可以是直流电场，也可以是脉冲电场 根据需要。 该项目的主要长期目标是 使用这些技术来提取详细的激发态信息 （例如，振动能量、偶极矩、pi pi* 和 npi* 原点 来自这些生物医学上重要的发色团的能量、耦合等）。 （现在特别有趣的是，我们似乎正在找到强有力的证据 对于其中一些中存在低能量 pi* lesser--- n 跃迁 简单卟啉）。 这项研究将涉及两名 MBRS 学生。 每个 一个人将负责一个单独的发色团并执行其 制备、纯化和运行低分辨率和中分辨率光谱。 激光 Stark 实验将用 PI 进行。 大多数光谱 目前这些发色团的可用数据分辨率较低，因为 电子能带的显着不均匀展宽。 光学的 烧孔、单点激发和斯塔克效应将提供 更清晰地了解这些具有生物医学重要性的电子状态 分子。