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

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(AuNPs).利用电化学和紫外-可见(UV-Vis)吸收光谱研究了pH和AuNPs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,Cytc和Cytc-AuNPs复合物的结构没有发生明显变化.当pH=2.0时,Cytc和Cytc-AuNPs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AuNPs能促进Cytc和电极之间的电子传输,与修饰了柠檬酸根的AuNPs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Cytc发生不可逆变性.AuNPs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.

Effect of pH and Au Nanoparticles on Cytochrome c Investigated by Electrochemistry and UV-Vis Absorption Spectroscopy

In this paper,gold nanoparticles(NPs)with an average size of(4.7±0.6)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.