电化学和紫外-可见吸收光谱法研究pH和金纳米粒子对细胞色素c的影响

摘要

In this paper, gold nanoparticles (NPs) with an average size of (4.7 ×.6) nm, capped with mercaptopropionic acid (MPA) ligand, are prepared. The effect of Ph and Au NPs on cytochrome c (Cyt c) is investigated by electrochemistry and UV-Vis absorption spectroscopy. UV-Vis absorption spectra indicate that the structures of Cyt c and Cyt c-Au NPs complex do not change appreciably between Ph=7.5 and Ph=3.0, but their Soret band positions change markedly at Ph=2.0, indicating that low Ph value induces a conformational change in Cyt c. Cyclic voltammetry (CV) result shows that Au NPs capped with MPA enhance electron transfer between Cyt c and the electrode. The data also reveals that the biocompatibility of Au NPs is improved when citric acid ligand is replaced with MPA. The change in Ph value causes a change of peak currents in CV and a shift of peak potential. When Ph value deviates from 7.0, levels of electroactive Cyt c decrease. Significant Ph change induces irreversible denaturing of Cyt c. The Ph at which Cyt c-Au NPs complex denatures completely is one unit higher than that of Cyt c. Combining the results from UV-Vis spectroscopy and CV, we find that addition of Au NPs makes adsorbing state Cyt c more vulnerable to Ph.%制备了粒径均匀、平均粒子尺度为(4.7±0.6) nm,表面修饰3-巯基丙酸(MPA)的金纳米粒子(Au NPs).利用电化学和紫外-可见(UV-Vis)吸收光谱研究了pH和Au NPs对细胞色素c(Cytc)结构的影响.UV-Vis吸收光谱结果表明,pH为7.5-3.0时,Cyt c和Cyt c-Au NPs复合物的结构没有发生明显变化.当pH=2.0时,Cyt c和Cyt c-Au NPs复合物的Soret谱峰位置均发生明显移动,说明pH诱导其构象发生变化.循环伏安(CV)结果表明,表面修饰了MPA的Au NPs能促进Cyt c和电极之间的电子传输,与修饰了柠檬酸根的Au NPs相比,其生物兼容性更好.pH的变化会引起CV中Cytc峰电流的改变和峰电位的移动.随着pH值的降低,Cytc电活性的量逐渐减小,并且pH诱导Cyt c发生不可逆变性.Au NPs的引入使自由态的Cytc耐酸性增强,而使得吸附态的Cytc耐酸能力减弱.