Understanding How Thiolates Promote Dioxygen Chemistry

了解硫醇盐如何促进双氧化学

• 批准号: 10444825
• 负责人: Julia A Kovacs
• 金额: $ 42.82万
• 依托单位: UNIVERSITY OF WASHINGTON
• 依托单位国家: 美国
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-05-01 至 2026-03-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10444825
• 关键词: Acute; Affect; Amines; Anabolism; Azides; Bacteria; Bacterial Infections; Binding; Binding Sites; Bond-It; Cancerous; Cations; Chemistry; Complex; Coupled; Crystallization; Cysteine; Cysteine dioxygenase; Deuterium; Dioxygen; Electrochemistry; Electron Transport; Enzymes; Freezing; Goals; Hydrogen; Hydrogen Bonding; Hydrogenase; In Situ; Iron; Isomerism; Isotopes; Kinetics; Ligands; Liquid substance; Measures; Modeling; Monitor; Monobactams; Mossbauer Spectroscopy; Neoplasm Metastasis; Nitrogen; Oxidation-Reduction; Oxygen; Pathway interactions; Play; Positioning Attribute; Production; Protons; Reaction; Reporting; Resistance; Source; Spectrum Analysis; Sulfur; Testing; Time; Tumor Suppressor Proteins; Vertebral column; Work; absorption; analog; antineoplastic antibiotics; aqueous; beta-Lactams; carbene; cold temperature; cryogenics; density; enzyme mechanism; experimental study; fighting; follow-up; instrument; isopenicillin N; nervous system disorder; novel anticancer drug; oxidation; prevent; scaffold; small molecule; time interval; tumor; vibration; weapons

Project Summary Cysteinate-ligated non-heme iron superoxo intermediates (RS-FeIII-O2•–) play a key role in the mechanisms of isopenicillin N-synthase (IPNS) and cysteine dioxygenase (CDO). The former provides our only source of β- lactam antibiotics, and the latter is known to prevent metastases of cancerous tumors and neurological disorders. Very little is known about the mechanisms of these reactions, the understanding of which will facilitate the synthesis of new anticancer drugs and antibiotics to which bacteria are not yet resistant. Very few well- characterized FeIII-O2•– compounds have been reported, and only two include a thiolate in the coordination sphere. Our group reported the first and only example of an RS-FeIII-O2•– capable of cleaving strong C-H bonds on par with cysteine β-C-H bond cleaved by IPNS. The goal of the work proposed herein will be to determine whether ligand constraints can be used to alter the reaction pathway of our RS-FeIII-O2•– from that of IPNS to that of CDO. We will incorporate β-hydrogens into our aliphatic thiolate ligand and determine whether intramolecular β C-H bond cleavage occurs, and β-deuteriums to see if that stabilizes the FeIII-O2•–, and if so, determine the kinetic isotope effect to provide additional support for intramolecular β-C-H bond cleavage. We will determine whether the trans thiolate influences the potency of our RS-FeIII-O2•– with respect to C-H bond cleavage by exploring the O2 chemistry of our mixed alkoxide/thiolate-ligated FeII complex. We will use Mossbauer spectroscopy and spectro-electrochemistry to provide evidence for the involvement of proton coupled electron transfer in the conversion of our putative high valent O=(R)S-FeIV=O to the corresponding O=(R)S-FeIII-OH and obtain the FeIIIO–H bond strength from the slope of the Pourbaix (pH vs E1/2) diagram. We will also examine the effects of redox inactive Lewis acidic cations and protons on the ability of our crystallographically characterized cis RS-FeIV=O to cleave strong C-H bonds, and determine how the thiolate affects this reactivity by synthesizing the corresponding cis RO-FeIV=O compound and examining pH-dependent redox potentials using spectro- electrochemistry and comparing the O–H bond strengths, obtained from the slope of the Pourbaix (pH vs E1/2) diagram, for cis RO-FeIII-OH versus cis RS-FeIII-OH. We will insert a methylene group into the ligand scaffold of our crystallographically characterized cis RS-FeIV=O to determine whether ligand constraints prevent intramolecular oxo atom transfer. Lastly, we will determine whether the synergistic interaction between a 𝛑- donating thiolate and 𝛑-accepting CO ligands facilitates hydrogenase (H2-ase) promoted H2 production and H2 cleavage.

项目概要 半胱氨酸连接的非血红素铁超氧中间体 (RS-FeIII-O2•–) 在机制中发挥关键作用 异青霉素 N-合酶 (IPNS) 和半胱氨酸双加氧酶 (CDO)。前者提供了我们唯一的β-来源 内酰胺抗生素，已知后者可以预防癌性肿瘤和神经系统疾病的转移。 人们对这些反应的机制知之甚少，了解这些反应将有助于 合成新的抗癌药物和细菌尚未产生耐药性的抗生素。很少有好的—— 已报道了具有特征的 FeIII-O2•– 化合物，并且只有两种在配位中包含硫醇盐 领域。我们的小组报告了第一个也是唯一一个能够裂解强 C-H 键的 RS-FeIII-O2•– 的例子 与 IPNS 裂解的半胱氨酸 β-C-H 键相同。本文提出的工作目标是确定 是否可以使用配体约束来改变我们的 RS-FeIII-O2•– 的反应途径，从 IPNS 改为 CDO 的。我们将把 β-氢结合到我们的脂肪族硫醇盐配体中，并确定分子内是否 发生 β C-H 键断裂，并用 β-氘检查是否稳定 FeIII-O2•–，如果是，则确定 动力学同位素效应为分子内 β-C-H 键裂解提供额外支持。我们将确定 反式硫醇盐是否影响我们的 RS-FeIII-O2•– 在 C-H 键裂解方面的效力 探索我们的混合醇盐/硫醇盐连接的 FeII 复合物的 O2 化学。我们将使用穆斯堡尔 光谱学和光谱电化学为质子耦合电子的参与提供证据 将我们假定的高价 O=(R)S-FeIV=O 转化为相应的 O=(R)S-FeIII-OH 并 从 Pourbaix（pH 与 E1/2）图的斜率获得 FeIIIO-H 键强度。我们还将检查 氧化还原惰性路易斯酸性阳离子和质子对我们晶体学表征能力的影响 cis RS-FeIV=O 以裂解强 C-H 键，并通过合成确定硫醇盐如何影响这种反应性 相应的顺式 RO-FeIV=O 化合物并使用光谱检查 pH 依赖性氧化还原电位 电化学并比较 O-H 键强度，从 Pourbaix 斜率获得（pH 与 E1/2） 图表，顺式 RO-FeIII-OH 与顺式 RS-FeIII-OH。我们将在配体支架中插入一个亚甲基 我们的晶体学特征 cis RS-FeIV=O 以确定配体限制是否阻止 分子内氧原子转移。最后，我们将确定 𝛑- 之间是否存在协同相互作用 提供硫醇盐和𝛑-接受 CO 配体促进氢化酶 (H2-ase) 促进 H2 产生和 H2 分裂。