SULFUR SPECIATION IN PLANT LEAVES/LICHENS, AND STUDIES OF METAL-CYS COMPLEXES US

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 硫是植物的必需元素，可以转化为半胱氨酸，然后转化为其他硫代谢物。目前植物中硫代谢的研究受到目前鉴定硫物种的“湿化学”方法的严重限制，这种方法需要对样品进行消化/加热/销毁，并且只能提供相当不准确的“总有机”和“总无机”硫量。借助硫K边X射线吸收光谱(XAS)，我们将对完整植物叶片中存在的主要硫形态进行详细的形态分析，以阐明硫代谢的关键步骤。我们还将研究加拿大艾伯塔省地区的样本，这些地区暴露在有充分记录的广泛酸性气体排放中，以调查对硫代谢的影响。地衣只从空气中吸收硫磺，是酸气影响的很好的天然监测器。半胱氨酸及其衍生物在医学上用于重金属解毒。半胱氨酸是生物体中发现的21种氨基酸之一，它含有三个协调位点：氨基、硫醇和羧酸基。硫醇基团可以形成强键，并积累软的重金属离子。到目前为止，配位化学的研究主要集中在固态金属络合物上，主要通过元素分析、红外光谱和少数情况下的X射线结晶学进行研究。在接近生理条件的溶液中，人们对它的结构和配位知之甚少。我们将利用金属和硫XAS研究金属中心周围的局域结构，即金属与配体的键距、配位原子的数目和类型，以及铅、镉、汞和银等重金属与半胱氨酸及其衍生物形成的络合物中硫原子周围的电子环境。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Sulfur is an essential element for plants, being converted into cysteine and then to other sulfur metabolites. Current research on sulfur metabolism in plants is severely restricted by the present "wet chemistry" methods for identifying sulfur species, which require digestion/heating/destruction of the sample and only provide rather inaccurate "total organic" vs. "total inorganic" amounts of sulfur. By means of sulfur K-edge X-ray absorption spectroscopy (XAS) we will perform detailed speciation analyses of the major sulfur species present in intact plant leaves to clarify the key steps in the sulfur metabolism. We will also study samples from areas in Alberta, Canada, exposed to well-documented extensive sour gas emissions, to investigate the effects on the sulfur metabolism. Lichens, which only take up sulfur from the air, are great natural monitors for sour gas effects. Cysteine and its derivatives are medically used for heavy metal detoxification. Cysteine, one of 21 amino acids found in living organisms, contains three coordinating sites: the amino, thiol and carboxylate groups. The thiol group can form strong bonds and accumulate ions of soft, heavy metals. Coordination chemical studies have so far been focused on metal complexes in the solid state, mostly by elemental analysis, IR and in a few cases, X-ray crystallography. Little is known about the structure and coordination in solution, near to physiological conditions. We will use metal and sulfur XAS to study the local structure around the metal center, i.e. the metal-ligand bond distances, number and type of coordinating atoms, as well as the electronic environment around the sulfur atom in complexes of heavy metals, e.g. Pb, Cd, Hg and Ag, with cysteine and its derivatives.