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: 6217803
• 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/6217803
• 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.

本提案中所述的研究是本方案的延续、延伸和 根据我们目前的MBR赠款对正在进行的工作进行修改。 这是一项关于5K固体中简单的卟啉的研究。 用单格点研究它们的电子基态和激发态性质 激发、光学烧孔和斯塔克效应。最基本的 推动这项研究的假设是，激发态和 存在低能NPI*跃迁。在我们这一阶段的工作中， 这些分子的游离碱和金属络合物形式将被研究。 卟啉，氯化，四氮杂吗啡。这些简单的卟啉是母体 生物医学上重要部分的化合物(例如，亚铁血红素，细胞色素， 叶绿素和光动力光敏剂)。卟啉是并且已经 进行了积极的研究，但大部分光谱数据都是从房间中获得的 只产生宽带的温度溶液。我们的方法是 将分子放入正构烷烃主体晶体中；放在液氦中 获得了高分辨(约2 cm-1)的温度谱。这个 特定晶体环境中的分子光谱可以 采用单点激励隔离。这种高分辨率可以 通过使用光学烧孔，改进得更多。当一个分子是 溶解在基质中，其电子光谱是不均匀的 展宽；当使用窄带宽激光进行激励时， 有时可能在不均匀加宽的带子上烧孔； 空洞是由光化学、瞬时存储或分子引起的 重新定位。当单点光谱的窄带，或光学 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 单一混合晶体(卟啉/正构烷烃)或制造低温 玻璃般的解决方案。将样品浸入液态氮气或He和An中 获得吸收光谱或发射光谱。单点光谱被制作或 用窄带激光烧制和扫描光学孔。为了斯塔克 效应实验中，锥形取向的晶体被放置在 电极。电场既可以是直流的，也可以是脉冲的 视需要而定。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、圆周率pi*和npi*原点 能量、耦合等)来自这些生物医学上重要的发色团。 (现在特别有趣的是，我们似乎找到了强有力的证据 对于其中一些中存在的低能pi*较少-n跃迁 简单的卟啉)。这项研究将涉及两名MBR学生。每个人 一个人将负责一个单独的发色团，并将执行其 制备、纯化并运行中低分辨率光谱。激光 斯塔克的实验将与PI一起进行。大部分的光谱 目前在这些发色团上获得的数据分辨率较低，因为 电子能带的显著不均匀展宽。光学 烧孔、单位激发和斯塔克效应将提供 更清楚地了解这些生物医学上重要的电子状态 分子。