BIOLOGICAL CHEMISTRY OF SULFUR AND SELENIUM

这项研究的主要目标是描述生物学特征， 硫和硒化学虽然生物化学 这两个基本要素一直是广泛研究的主题， 一些对它们的生物化学至关重要的反应还没有被 表征了此外，由于生物系统的复杂性，大多数 研究已经在水溶液中使用高度纯化的化合物。在 最先进的高场核磁共振技术 (NMR)光谱学和现代分离方法将用于 表征硫和硒的生物化学， 完整红细胞和水溶液中。 本申请中提出的研究的主要目的是 表征生物中二硫键的可逆形成 分子。二硫键的可逆形成被用于生物学 运输还原当量，调节新陈代谢， 对蛋白质的稳定性和作为细胞防御系统。有四 主要研究方向。(i)来描述 完整红细胞对巯基氧化引起的氧化应激的反应 通过硫醇/二硫键交换在外表面上的基团，以及 确定这作为减少血浆中 二硫化物，包括含硫醇药物的二硫化物， 卡托普利和青霉胺。(ii)为了开发非侵入性的方法， 通过NMR测量细胞内氧化还原电位。此类方法将 具有许多应用，例如测定硫醇的响应 肿瘤和其他组织中的系统进行放射和化学治疗。（三） 为了表征形成的动力学和热力学， 合成肽、肽激素和 巯基/二硫键交换反应。知识是 从这些研究中获得的信息将有助于制定有效的 在肽和蛋白质中形成二硫键的方法 “专为特定应用而设计”。 (iv)为了表征动力学 和细胞内巯基/二硫键交换反应的热力学 由巯基转移酶（TTase）催化。两者的氧化还原电位 将测定TTase活性位点的半胱氨酸残基， 酶催化反应的机理将被表征。 生物化学研究的长期目标 硒是决定为什么自然选择硒，而不是硫， 谷胱甘肽过氧化物酶（GSH-Px）的活性位点，并阐明 无机硒被纳入21世纪的机制 氨基酸硒代半胱氨酸在拟议的研究中， 含硒化合物的性质将在以下方面表征： 氧化还原反应的动力学和热力学。等 基本信息不仅有助于我们理解 为什么大自然选择硒作为GSH-Px的活性位点， 硒药物的可能发展。

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.