ELECTRONIC SPECTROSCOPY OF SIMPLE PORPHYRINS

简单卟啉的电子光谱

• 批准号: 6452771
• 负责人: LAWRENCE William JOHNSON
• 金额: $ 3.15万
• 依托单位: YORK COLLEGE
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-06-01 至 2002-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6452771
• 关键词: alkanes; bacteriorhodopsins; chemical synthesis; chlorin; chromophore; dipole moment; electronic spectra; laser spectrometry; metal complex; metalloporphyrins; photochemistry; porphyrin structure

The research described here is a continuation and extension of work being carried out under our current MBRS grant. This is primarily a study of simple, unsubstituted porphyrins in the solid state at 5K with respect to their electronic ground and excited state proteins using site excitation, optical hole-burning and the Stark effect. The fundamental hypothesis of this research is that excited states of porphyrins are more complex than is currently recognized. Porphyrins have been actively studied for years, but most of the spectroscopic data is from room temperature solutions which yield broad bands. Our approach is to place the molecules in n-alkane host crystals or low temperature glasses at liquid helium temperatures. High resolution (approximately 2 cm/-1) spectra can be obtained using single sit excitation or optical hole-burning. When the narrow bands of single site spectra, or optical holes are coupled with the Stark effect, they provide a sensitive probe of molecule's electronic states. We plan to continue to study free base and metal complex forms of these simple molecules (e.g. porphin, chlorin, isobacteriochlorin); they are parent compounds of biomedically important moieties (e.g. hemes, chlorophylls). Of particular interest now in the electronic structure of the simple porphyrins, is that we have found evidence for vibronic coupling between the first and second excited states and for the presence of low energy pi*- n transitions. Both of these observations will be studied further with Stark effect experiments. However, now we will also begin to use our expertise in obtaining high resolution electronic spectra, and the detailed spectral information which we previously obtained on simple prophyrins, to examine the electronic states of biomedically active porphyrin based moieties. Because of our extensive experience with isobacteriochlorin we will start this initiative with sulfite reductase; this enzyme is characterized by the presence of an iron siroheme (iron isobacteriochlorin) exchanged coupled to a Fe4S4 cluster. The primary, long-term objective of this project is to extract detailed ground and excited state information (e.g. vibrational energies, dipole moments, pi/pi* and npi* origin energies, coupling, etc.) from biomedically important porphyrin chromophores and understand their electronic structure.

此处描述的研究是根据我们目前的MBR赠款进行的工作的延续和扩展。这主要是对使用位点激发，光孔燃烧和鲜明的效果相对于其电子地面和激发态蛋白质的简单，未取代的卟啉的研究。这项研究的基本假设是，卟啉激发态比目前认识到的更为复杂。多年来，对卟啉进行了积极研究，但是大多数光谱数据来自产生宽带的室温溶液。我们的方法是将分子放在液体氦气温度下的N-烷烃宿主晶体或低温玻璃杯中。可以使用单点激发或光孔燃烧来获得高分辨率（约2 cm/-1）光谱。当单位光谱的狭窄带或光孔与鲜明的效果相结合时，它们提供了对分子电子状态的敏感探针。我们计划继续研究这些简单分子的自由碱基和金属复合形式（例如卟啉，氯蛋白，等杆菌氯肽）；它们是生物医学重要的部分的母体化合物（例如Hemes，叶绿素）。现在，在简单卟啉的电子结构中特别感兴趣的是，我们发现了第一和第二激发态之间振动耦合以及存在低能PI*-N跃迁的证据。这两个观察结果将通过Stark效应实验进一步研究。但是，现在，我们还将开始使用我们的专业知识来获得高分辨率电子光谱，以及先前在简单的先知蛋白上获得的详细光谱信息，以检查基于生物医学活性卟啉的基于的基于生物医学活跃的基于的电子状态。由于我们在等亚氯氯氯此方面的丰富经验，我们将使用亚硫酸盐还原酶开始这项计划。该酶的特征在于存在与Fe4S4簇耦合的铁siroheme（铁等异氯氯）。该项目的主要长期目标是从生物医学上重要的卟啉发色团中提取详细的地面和激发态信息（例如振动能，偶极矩，Pi/Pi*和NPI*原点，耦合等）并了解其电子结构。