BIOLOGICAL CHEMISTRY OF SULFUR AND SELENIUM

这项研究的广泛目标是描述生物的特征 硫和硒的化学。尽管生物化学 这两个基本要素一直是广泛研究的主题， 它们的生物化学反应中的一些核心反应还没有 特色化的。此外，由于生物系统的复杂性，大多数 研究已经在水溶液中使用了高纯度的化合物。在 拟议的研究，最先进的高场核磁共振 (核磁共振)光谱和现代分离方法将用于 硫和硒的生物化学特征 完整的红细胞和水溶液中。 本申请中提出的研究的一个主要目标是 表征生物中二硫键的可逆形成 分子。二硫键的可逆形成在生物学中的应用 运输还原等价物，调节新陈代谢，提供 对蛋白质和作为细胞防御系统的稳定性。一共有四个 建议研究的主要部分。(I)描述以下方面的反应： 完整红细胞对硫醇氧化所致氧化应激的影响 通过硫醇/二硫化物交换在外表面上基团，并 确定这作为降低血浆浓度的机制的意义 二硫化物，包括含有硫醇的药物的二硫化物，如 卡托普利和青霉胺。(Ii)开发非侵入性治疗方法 核磁共振测定细胞内氧化还原电势。这些方法将 有许多应用，例如测定硫醇的响应 肿瘤和其他组织中的系统对放射和化疗的敏感性。(Iii) 以表征形成和形成的动力学和热力学 合成肽、肽激素和合成肽中二硫键的还原 通过硫醇/二硫键交换反应产生的神经毒素。即将到来的知识 通过这些研究，将有助于开发有效的 多肽和蛋白质中二硫键的形成方法 专为特定应用而设计。(四)确定动力学特征 和细胞内硫醇/二硫键交换反应的热力学 由硫醇转移酶(TTase)催化。两者的氧化还原电势 将测定TTase活性部位的半胱氨酸残基，并 将对该酶催化反应的机理进行表征。 生物化学研究的远期目标 硒决定了为什么大自然选择了硒，而不是硫， 谷胱甘肽-过氧化物酶(GSH-Px)的活性部位及阐明 无机硒进入21世纪的机制 氨基酸，硒半胱氨酸。在拟议的研究中，基本的 含硒化合物的性质将用下列术语来表征 他们的氧化还原反应的动力学和热力学。是这样的 基本信息不仅有助于我们理解 为什么自然界选择硒作为GSH-PX的活性部位，也是为了 有可能开发出新的硒芯片。

The broad objectives of this research are to characterize the biological chemistry of sulfur and selenium. Although the biological chemistry of these two essential elements has been the subject of extensive research, some reactions central to their biological chemistry have not been characterized. Also, because of the complexity of biological systems, most studies have used highly purified compounds in aqueous solution. In the proposed research, state-of-the-art high field nuclear magnetic resonance (NMR) spectroscopy and modern separation methods will be used to characterize the biological chemistry of sulfur and selenium both in intact red blood cells and in aqueous solution. A major objective of the research proposed in this application is to characterize the reversible formation of disulfide bonds in biological molecules. The reversible formation of disulfide bonds is used in biology to transport reducing equivalents, to regulate metabolism, to provide stability to proteins and as a cellular defense system. There are four major parts to the proposed research. (i) To characterize the response of intact red blood cells to oxidative stress caused by oxidation of thiol groups on the exofacial surface by thiol/disulfide exchange, and to determine the significance of this as a mechanism for reduction of plasma disulfides, including disulfides of thiol-containing drugs such as captopril and penicillamine. (ii) To develop methods for the noninvasive measurement of intracellular redox potential by NMR. Such methods will have many applications, for example to determine the response of thiol systems in tumors and other tissues to radiation and chemotherapy. (iii) To characterize the kinetics and thermodynamics of the formation and reduction of disulfide bonds in synthetic peptides, peptide hormones and neurotoxins by thiol/disulfide exchange reactions. The knowledge to be gained from these studies will contribute to the development of effective methods for the formation of disulfide bonds in peptides and proteins "engineered" for specific applications. (iv) To characterize the kinetics and thermodynamics of intracellular thiol/disulfide exchange reactions catalyzed by thioltransferase (TTase). The redox potential of the two cysteine residues at the active site of TTase will be determined and the mechanism of the enzyme catalyzed reactions will be characterized. The long term objectives of the research on the biological chemistry of selenium are to determine why nature chose selenium, rather than sulfur, for the active site of glutathione-peroxidase (GSH-Px) and to elucidate the mechanism by which inorganic selenium is incorporated into the 21st amino acid, selenocysteine. In the proposed research, the fundamental properties of selenium-containing compounds will be characterized in terms of the kinetics and thermodynamics of their redox reactions. Such fundamental information will contribute not only to our understanding of why nature chose selenium for the active site of GSH-Px but also to the possible development of selenodrugs.