X RAY AND CHEMICAL STUDIES OF METALLOPORHYRINS

提出了一系列新型金属卟啉化合物的合成与表征方法。 这项工作将强调但不限于铁卟啉衍生物。 提出用于研究的大多数类别的化合物与发展对血红素蛋白衍生物的理解有关，血红素蛋白衍生物执行广泛的生物学功能，包括氧利用和运输、基于NO的信号传导、电子传递、药物代谢和各种其他酶促过程。 另一类衍生物与对光合反应重要的物种有关。 三维X射线晶体结构测定的方法将被应用于确定分子结构和金属卟啉立体化学的各个细节方面。 其他适用的方法包括通过体温度依赖性磁化率和电子顺磁共振（EPR）测量表征磁性。 Mssbauer光谱，振动和UV-vis-near-IR光谱，电化学性质和分子力学计算。研究目标，在最广泛的条款，是实现金属卟啉的结构和物理性质的合成，特别是因为这些关系涉及到基于血红素的生物过程的理解。 在某种程度上，这将是通过建立可能的立体化学特征的金属卟啉基团在其生物环境中，并模拟特定的辅基的行为选择血红素蛋白。 这些研究有望提供蛋白质结构如何调节金属卟啉几何形状以及如何用相同的基本铁原卟啉IX单元进行各种各样的生物过程的理解。 要研究的铁卟啉酸盐包括合成类似物的双（组氨酸）-连接的细胞色素B和C，以检查功能，如轴向配体取向如何影响其电子结构和氧化还原性能。另一个重要的研究目标是探索金属卟啉中的电子相互作用;详细的研究将研究具有潜在的分子内和/或分子间途径的系统中的耦合。 这些研究包括具有氧化或还原卟啉核的物质，其中π-自由基自旋耦合是显著的。

The synthesis and characterization of a variety of new metalloporphyrin compounds is proposed. The work will emphasize, but will not be limited to, iron porphyrinate derivatives. Most classes of compounds proposed for study are related to developing an understanding of hemoprotein derivatives, which carry out a wide range of biological functions including oxygen utilization and transport, NO-based signaling, electron transport, drug metabolism and a variety of other enzymatic processes. Another class of derivatives is related to species important to photosynthetic reactions. The methods of three-dimensional X-ray crystal structure determination will be applied to define molecular structures and various detailed aspects of metalloporphyrin stereochemistry. Other methodologies to be applied, as appropriate, include characterization of magnetic properties by bulk temperature-dependent susceptibility and electron paramagnetic resonance (EPR) measurements. Mssbauer spectroscopy, vibrational and UV-vis-near-IR spectroscopy, electrochemical properties, and molecular mechanics calculations. The research objectives, stated in the broadest terms, are to achieve a synthesis of the structural and physical properties of metalloporphyrins, particularly as these relationships pertain to an understanding of hemoprotein-based biological processes. In part, this will be accomplished by establishing possible stereochemical features of a metalloporphyrin group in its biological environment and to model specific prosthetic group behavior of selected hemoproteins. Such studies are expected to provide understanding of how protein structures could modulate metalloporphyrin geometry and how a wide variety of biological processes can be carried out with the same fundamental iron protoporphyrin IX unit. Iron porphyrinates to be studied include synthetic analogues of bis(histidine)-ligated cytochromes b and c to examine how features such as axial ligand orientation affect their electronic structure and oxidation-reduction properties. Another significant research objective is the exploration of electronic interactions in metalloporphyrins; detailed studies will examine coupling in systems with potential intra- and/or intermolecular pathways. Included in such studies are species with oxidized or reduced porphyrin cores in which pi-radical spin coupling is significant.