Pulsed EPR Studies of Biological Manganese Clusters

生物锰簇的脉冲 EPR 研究

• 批准号: 8005178
• 负责人: R David Britt
• 金额: $ 15.3万
• 依托单位: UNIVERSITY OF CALIFORNIA AT DAVIS
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-01-07 至 2011-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8005178
• 关键词: Amino Acids; Applications Grants; Binding; Biological; Biology; Chemistry; Complex; Couples; Electron Nuclear Double Resonance; Electron Spin Resonance Spectroscopy; Electrons; Enzymes; Food; Freezing; Frequencies; Goals; Lasers; Life; Ligation; Location; Manganese; Medicine; Metals; Methods; Molecular; Mutagenesis; Oxidation-Reduction; Oxygen; Physiologic pulse; Plants; Play; Process; Protons; Research; Resolution; Respiration; Role; Sampling; Source; Spectrum Analysis; Structure; System; Technology; Transition Elements; Water; atmospheric carbon dioxide; cofactor; design; instrument; interest; millisecond; oxidation; photosystem II; planetary Atmosphere; research study; tyrosine radical

DESCRIPTION (provided by applicant): The transition metal manganese plays a variety of important roles in biology and medicine. For example, a large number of enzymes use Mn(ll) in their catalytic centers. Along with Mn(ll), the higher oxidation states, Mn(lll) and Mn(IV), are also used in crucial oxygen-centered redox chemistry. Of particular interest is the unique water oxidation chemistry enabled by the tetranuclear Mn cluster of the oxygen evolving complex (OEC) of photosystem II. This cluster couples the high oxidation potential of a proximal tyrosine radical (Yz() to the oxidation of two bound waters, releasing molecular oxygen at the final step of a 5-intermediate cycle. Thus this system is an important example of metalloradical chemistry, and the fact that each state can be generated in high yield with laser flashes makes this photosynthetic system ideal for exploring this intriguing chemistry. We will examine the intermediates of the oxygen evolving cycle with multifrequency (9, 31, 35, and 130 GHz) advanced electron paramagnetic resonance (EPR) methods, including ENDOR, ESEEM, and HYSCORE. These experiments will target the structure of the Mn cluster, its amino acid coordination, the location and function of the Ca2+ and Cl- cofactors, and the binding of substrate waters. We will follow leads from new x-ray crystal structures to target specific issues of high current interest. We will use our high field/frequency (130 GHz) EPR/ENDOR instrument to perform high resolution spectroscopy of the Mn cluster in single crystals of photosystem II. Using a newly assembled rapid freeze quench system, we will cryotrap samples on the millisecond timescale after laser flash sequences, with the ultimate goal of characterizing the final short-lived S4-state of the OEC cycle. This research promises to reveal important new details concerning how a biological metal cluster can produce molecular oxygen from water with an efficiency far greater than we can achieve with our current technologies. Relevance: This grant proposal focuses on understanding this vital life process, which produces the oxygen of our atmosphere that we require for respiration, and biologically activates the electrons and protons from water needed by plants to convert atmospheric carbon dioxide into our primary food sources.

描述（由申请人提供）：过渡金属锰在生物学和医学中发挥着多种重要作用。例如，大量酶在其催化中心使用Mn(II)。与 Mn(II) 一起，较高氧化态的 Mn(III) 和 Mn(IV) 也用于关键的以氧为中心的氧化还原化学。特别令人感兴趣的是由光系统 II 的析氧络合物 (OEC) 的四核 Mn 簇实现的独特的水氧化化学。该簇将近端酪氨酸自由基 (Yz() 的高氧化电位与两个结合水的氧化结合起来，在 5-中间循环的最后一步释放分子氧。因此，该系统是金属自由基化学的一个重要例子，并且事实上，每个状态都可以通过激光闪光以高产率产生，这使得该光合作用系统非常适合探索这种有趣的化学反应，我们将用多频率（9、31、 35 和 130 GHz）先进的电子顺磁共振 (EPR) 方法，包括 ENDOR、ESEEM 和 HYSCORE 这些实验将针对 Mn 簇的结构、其氨基酸配位、Ca2+ 和 Cl- 辅助因子的位置和功能。 ，以及基质水的结合，我们将跟踪新的 X 射线晶体结构的线索，以解决当前关注的特定问题。我们将使用我们的高场/频率 (130 GHz) EPR/ENDOR 仪器。对光系统 II 单晶中的 Mn 簇进行高分辨率光谱分析。使用新组装的快速冷冻淬火系统，我们将在激光闪光序列后以毫秒时间尺度冷冻捕获样品，最终目标是表征 OEC 循环的最终短暂 S4 状态。这项研究有望揭示有关生物金属簇如何从水中产生分子氧的重要新细节，其效率远远高于我们现有技术所能达到的效率。相关性：这项拨款提案的重点是了解这一重要的生命过程，该过程产生我们呼吸所需的大气中的氧气，并以生物方式激活植物所需的水中的电子和质子，将大气中的二氧化碳转化为我们的主要食物来源。