Departament de Química Analítica, Facultat de Química Universitat de Barcelona, Martí i Franquès 1-11, E-08028 Barcelona, Spain.
Metallomics. 2011 Aug;3(8):838-46. doi: 10.1039/c1mt00028d. Epub 2011 Jun 20.
Isothermal Titration Calorimetry (ITC) was used to study the binding of Cd(2+) by phytochelatins ((γGlu-Cys)(n)-Gly, PC(n); n = 1-5) and their selected fragments (Cys, Cys-Gly and γGlu-Cys) in order to understand the influence of the chain length on the complex stabilities and the origin of the enhanced affinities in Tris buffer at pH 7.5 and 8.5 and at 25 °C. Different complexes are formed with glutathione (GSH) and its fragments, Cys, Cys-Gly and γGlu-Cys, and their stabilities depend on the corresponding pK(a) value of the thiol group in the ligands. The stability of Cd-PC(n) complexes increases moving towards higher PC(2-5), as well as the complexing capacity expressed as the number of metal ions that can be bound by one ligand molecule. The affinity of Cd(2+) for the PC(n) can be described by the following GSH < PC(2) < PC(3)≤ PC(4)≤ PC(5) sequence. On the basis of these thermodynamic data it is possible to explain the abundance of certain Cd-PC(n) complexes found in nature. The comprehension of the thermodynamic rules that govern the interactions of Cd(2+) with PC(n) and their constituents is of great service in the research with real plant samples subjected to metal stress and in the development of new strategies of bio/phytoremediation.
等温热力学滴定法 (ITC) 被用于研究 Cd(2+)与植物螯合肽 ((γGlu-Cys)(n)-Gly, PC(n); n = 1-5) 及其选定片段 (Cys、Cys-Gly 和 γGlu-Cys) 的结合情况，以了解链长对复合物稳定性的影响以及在 pH 7.5 和 8.5 的 Tris 缓冲液中和 25°C 下增强亲和力的起源。与谷胱甘肽 (GSH) 及其片段 Cys、Cys-Gly 和 γGlu-Cys 形成不同的复合物，其稳定性取决于配体中巯基的相应 pK(a) 值。Cd-PC(n) 复合物的稳定性随着 PC(2-5) 的增加而增加，以及作为可以与一个配体分子结合的金属离子数的络合能力也增加。Cd(2+)与 PC(n)的亲和力可以用以下 GSH < PC(2) < PC(3)≤ PC(4)≤ PC(5) 顺序来描述。基于这些热力学数据，可以解释自然界中存在的某些 Cd-PC(n) 复合物的丰富度。理解控制 Cd(2+)与 PC(n)及其组成部分相互作用的热力学规则对于研究受金属胁迫的实际植物样品和开发新的生物/植物修复策略非常有帮助。
