Chemistry Department, Missouri University of Science and Technology, Rolla, MO 65401, United States.
J Colloid Interface Sci. 2012 Apr 1;371(1):144-9. doi: 10.1016/j.jcis.2011.12.052. Epub 2011 Dec 27.
Using antioxidants is an important means of treating lead poisoning. Prior in vivo studies showed marked differences between various chelator antioxidants in their ability to decrease both blood Pb(II) levels and oxidative stress resulting from lead poisoning. The comparative abilities of NAC and NACA to Pb(II) were studied in vitro, for the first time, to examine the role of the -OH/-NH(2) functional group in antioxidant binding behavior. To assay the antioxidant-divalent metal interaction, the antioxidants were probed as solid surfaces, adsorbing Pb(II) onto them. Surface characterization was carried out using X-ray photoelectron spectroscopy (XPS) analysis to quantify Pb(II) in the resulting adducts. XPS of the Pb 4f orbitals showed that more Pb(II) was chemically bound to NACA than NAC. In addition, the antioxidant surfaces probed via point-of-zero charge (PZC) measurements of NAC and NACA were obtained to gain further insight into the Pb-NAC and Pb-NACA binding, showing that Coulombic interactions played a partial role in facilitating complex formation. The data correlated well with solution analysis of metal-ligand complexation. UV-vis spectroscopy was used to probe complexation behavior. NACA was found to have the higher binding affinity as shown by free Pb(II) available in the solution after complexation from HPLC data. Electrospray ionization mass spectrometry (ESI-MS) was applied to delineate the structures of Pb-antioxidant complexes. Experimental results were further supported by density functional theory (DFT) calculations of supermolecular interaction energies (E(inter)) showing a greater interaction of Pb(II) with NACA than NAC.
使用抗氧化剂是治疗铅中毒的重要手段。先前的体内研究表明，各种螯合抗氧化剂在降低血铅（II）水平和减轻铅中毒引起的氧化应激方面的能力存在显著差异。首次在体外研究了 NAC 和 NACA 对 Pb（II）的比较能力，以研究-OH/-NH2 官能团在抗氧化剂结合行为中的作用。为了研究抗氧化剂-二价金属相互作用，将抗氧化剂作为固体表面，吸附 Pb（II）在它们上面。使用 X 射线光电子能谱（XPS）分析进行表面特性研究，以定量测定生成的加合物中的 Pb（II）。Pb 4f 轨道的 XPS 表明，NACA 与 Pb（II）的化学结合量多于 NAC。此外，通过 NAC 和 NACA 的零电荷点（PZC）测量来探测抗氧化剂表面，以进一步了解 Pb-NAC 和 Pb-NACA 结合，表明库仑相互作用在促进络合形成中起部分作用。数据与金属配体络合的溶液分析很好地相关。使用紫外可见光谱法（UV-vis）来探测络合行为。从 HPLC 数据可知，NACA 具有更高的结合亲和力，即络合后溶液中剩余的游离 Pb（II）。应用电喷雾电离质谱（ESI-MS）来描绘 Pb-抗氧化剂络合物的结构。实验结果进一步得到密度泛函理论（DFT）计算的超分子相互作用能（E(inter)）的支持，表明 Pb（II）与 NACA 的相互作用大于 NAC。
