Conformationally-flexible, reactive manganese clusters to probe possible mechanisms of oxygen-oxygen bond formation in photosystem II

在地球生命发展的早期阶段，也许最重要的进化突破是蓝藻和现代植物的古老祖先在阳光驱动下将水氧化成氧气。这些生物发现了一种方法，利用海洋表面几乎无限的水和阳光来制造自己的食物。就科学所知，生物只发现了一种方式来完成水的氧化过程，现代植物和光合生物可能仍在使用数十亿年前相同的进化创新，尽管可能已经显著进化。进行这种反应的酶被称为光系统II，尽管这种反应对生物和能源领域至关重要，但关于这种酶的工作原理仍然存在许多问题。Zdilla教授正致力于建立酶活性位点的分子模型，这是一个含有锰和钙的立方体形状的金属原子簇。Zdilla教授开发的工作模型可能会让我们了解光合生物是如何进行这一重要反应的。Zdilla教授通过在费城科学节和费城小学的演讲，继续他对青年和成人社区的参与。Zdilla教授还开发了教育晶体学在线资源数据库（DECOR），这是一个免费的，可下载的晶体学研究教育材料来源。地球上细胞能量的主要来源是太阳，它的可见光能量被光合作用的生物体收集，驱动水氧化成O2，并驱动二氧化碳（CO2）随之减少为有机分子，然后用作燃料和生物结构的原材料。光催化水氧化耦合质子还原也是产生可持续太阳能燃料的重要目标。负责生物水氧化反应的酶是光系统II (PSII)，它是一种多亚基酶，含有四锰-钙-氧簇作为催化活性位点。由于酶的复杂性，直接研究酶往往是一个挑战，生物无机化学家经常转向仿生模型复合物。尽管有数百个合成锰氧簇的例子，但很少显示出令人信服的PSII模型的反应性。Zdilla教授和他的团队通过优先考虑低配位数（提供水结合位点）和簇灵活性（促进分子重排），开发了设计仿生锰簇的新方法。这些方法导致了团簇执行各种各样的困难反应，包括N-N， C-H， C-N和O=O键形成/断裂反应，以及催化水氧化。本项目旨在进一步研究它们的分子机制，这可能有助于了解酶的功能，并为如何设计具有能量目的的优质水氧化催化剂提供线索。Zdilla教授通过在费城科学节和费城小学的演讲，继续他对青年和成人社区的参与。Zdilla教授还开发了教育晶体在线资源数据库（DECOR），这是晶体学研究的免费教育材料来源。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

In the early stages of the development of life on earth, perhaps the most significant evolutionary breakthrough was the sunlight-driven oxidation of water to oxygen (O2) by the ancient ancestors of cyanobacteria and modern plants. These organisms discovered a way to make their own food using the virtually limitless supply of water and sunlight available near the surface of the oceans. As far as science knows, organisms have found only one way to perform this water oxidation process, and it is possible that modern plants and photosynthetic organisms are still using that same evolutionary innovation from billions of years ago, although presumably significantly evolved. The enzyme that performs this reaction is called Photosystem II, and despite the central importance of this reaction to the fields of biology and energy, many questions remain about how this enzyme works. Professor Zdilla is working to build molecular models of the enzyme active site, which is a cube-shaped cluster of metal atoms containing manganese and calcium. The working models developed by Professor Zdilla may lead to insights on how photosynthetic organisms are able to perform this important reaction. Professor Zdilla continues his community engagement of youth and adult communities through talks during the Philadelphia Science Festival and at Philadelphia elementary schools. Professor Zdilla also develops the Database of Educational Crystallographic Online Resources (DECOR), a free, downloadable source of educational materials for the study of crystallography. The primary source of cellular energy on earth is the sun, whose visible light energy is harvested by photosynthetic organisms to drive the oxidation of water to O2 and drive the concomitant reduction of carbon dioxide(CO2) to organic molecules, which are then used as fuel and as raw materials for the construction of living things. Photocatalytic water oxidation coupled to proton reduction is also an important goal for the generation of sustainable solar fuels. The enzyme responsible for the biological water oxidation reaction is photosystem II (PSII), a multi-subunit enzyme containing a tetramanganese-calcium-oxo cluster as the catalytic active site. Since enzymes are often a challenge to study directly due to their complexity, bioinorganic chemists frequently turn to biomimetic model complexes. Despite hundreds of examples of synthetic manganese oxo-cluster, very few show compelling reactivity that models PSII. Professor Zdilla and his group develop new approaches to designing biomimetic manganese clusters by prioritizing low-coordination number(to provide water binding sites) and cluster flexibility (to promote molecular rearrangement). These approaches have resulted in clusters that perform a diverse set of difficult reactions including N-N, C-H, C-N, and O=O bond making/breaking reactions, and catalytic water oxidation. This project seeks to further mechanistically investigate their molecular mechanisms, which may inform understanding of the function of the enzyme, and provide clues on how to design superior water oxidation catalysts for energy purposes. Professor Zdilla continues his community engagement of youth and adult communities through talks during the Philadelphia Science Festival and at Philadelphia elementary schools. Professor Zdilla also develops the Database of Educational Crystallographic Online Resources (DECOR), a free source of educational materials for the study of crystallography.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.