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: 6271614
• 负责人: LAWRENCE William JOHNSON
• 金额: $ 18.63万
• 依托单位: YORK COLLEGE
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-06-01 至 1999-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6271614
• 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.

该提案中描述的研究是延续，扩展和 修改我们目前的MBR赠款进行的工作。 这是一项针对5K固态中简单卟啉的研究 他们使用单个位点的电子地面和激发状态特性 激发，光孔燃烧和鲜明的效果。 基本 推动这项研究的假设是激发状态和 低能NPI*过渡的存在。 在我们的工作阶段 将研究这些分子的自由碱基和金属复合形式：例如 斑岩，氯磷脂，四氮嗪。 这些简单的卟啉是父母 生物医学重要的部分的化合物（例如，hemes，细胞色素， 叶绿素和光动力光敏剂）。 卟啉是并且有 被积极研究，但是大多数光谱数据sis来自房间 温度解决方案仅产生宽带。 我们的方法是 将分子放在n-烷烃宿主晶体中；在液体氦气中 获得高度分辨（约2 cm-1）光谱的温度。 这 然后可以在特定晶体环境中的分子光谱 通过使用单个站点兴趣隔离。 这个高分辨率可以是 通过使用光孔燃烧，可以进一步改善。 当分子是 溶解在基质中，其电子光谱不均匀 扩大；当使用狭窄的带宽激光进行激发时，它是 有时可能会在不均匀的宽带中燃烧孔； 孔由光化学，瞬态存储或分子产生 重新定位。 当单个位点光谱的狭窄带或光学带 孔与鲜明的效果相结合，它们提供了敏感的特点 分子电子状态。 我们的整体方法涉及增长 单一混合晶体（卟啉/N-烷烃）或使低温 玻璃解决方案。 样品浸入液体N2或HE和 获得的吸收或发射光谱。 制作单个站点光谱或 光孔被窄带激光燃烧并扫描。 对于史塔克 效应实验，将面向仪的晶体放置在 电极。 电场可以应用直流或脉冲 取决于需求。 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，偶极矩，pi pi*和npi*起源 来自这些在生物医学上重要的发色团中的能量，耦合等。 （现在特别有趣的是，我们似乎正在寻找有力的证据 对于低能pi*的存在，其中一些过渡 简单的卟啉）。 这项研究将涉及两名MBRS学生。 每个 一个人将负责单独的发色团，并将执行 制备，纯化并运行低和中分辨率光谱。 激光 PI将进行Stark实验。 大多数光谱学 这些发色团现在可用的数据是低分辨率的 电子带的实质性不均匀拓宽。 光学的 漏洞，单位点激发和鲜明的效果将提供 这些生物医学重要的电子状态的清晰图片 分子。