Department of Chemistry, Mississippi State University, Mississippi State, Mississippi 39762, USA.
Langmuir. 2013 Sep 3;29(35):10990-6. doi: 10.1021/la402239h. Epub 2013 Aug 21.
The role of cysteine residues in the protein binding kinetics and stability on gold nanoparticles (AuNP) was studied using AuNP localized surface plasmon resonance (LSPR) in combination with an organothiol (OT) displacement method. GB3, the third IgG-binding domain of protein G, was used to model protein-AuNP adsorption. While wild-type GB3 (GB30) contains no cysteine residues, bioengineered GB3 variants containing one (GB31) and two (GB32) cysteine residues were also tested. The cysteine content has no significant effect on GB3 binding kinetics with AuNPs, and most protein adsorption occurs within the first few seconds upon protein/AuNP mixing. However, the stability of GB3 on the AuNP surface against OT displacement depends strongly on the cysteine content and the age of the AuNP/GB3 mixture. The GB30 covered AuNPs can be completely destabilized and aggregated by OTs, regardless of the age of the GB30/AuNP mixtures. Long-time incubation of GB31 or GB32 with AuNPs can stabilize AuNPs against the OT adsorption inducted aggregation. This study indicates that multiple forces involved in the GB3/AuNP interaction, and covalent binding between cysteine and AuNP is essential for a stable protein/AuNP complex.
使用金纳米粒子（AuNP）局部表面等离子体共振（LSPR）结合有机硫醇（OT）置换法研究半胱氨酸残基在蛋白质与 AuNP 结合动力学和稳定性中的作用。GB3 是蛋白 G 的第三个 IgG 结合结构域，用于模拟蛋白-AuNP 吸附。野生型 GB3（GB30）不含半胱氨酸残基，而含有一个（GB31）和两个（GB32）半胱氨酸残基的工程 GB3 变体也进行了测试。半胱氨酸含量对半胱氨酸含量对 GB3 与 AuNP 结合动力学没有显著影响，并且大多数蛋白质吸附发生在蛋白质/AuNP 混合后的最初几秒钟内。然而，GB3 在 AuNP 表面上对 OT 置换的稳定性强烈依赖于半胱氨酸含量和 AuNP/GB3 混合物的年龄。无论 AuNP/GB30 混合物的年龄如何，GB30 覆盖的 AuNP 都可以被 OT 完全去稳定和聚集。GB31 或 GB32 与 AuNP 长时间孵育可以稳定 AuNP ，使其免受 OT 吸附诱导的聚集。这项研究表明，GB3/AuNP 相互作用涉及多种力，并且半胱氨酸与 AuNP 之间的共价结合对于稳定的蛋白/AuNP 复合物是必不可少的。
