Kamada Kai, Ito Daiki, Soh Nobuaki
Department of Chemistry and Materials Engineering, Graduate School of Engineering, Nagasaki University , Nagasaki 852-8521, Japan.
Faculty of Agriculture, Saga University , Saga 840-8502, Japan.
Bioconjug Chem. 2015 Oct 21;26(10):2161-6. doi: 10.1021/acs.bioconjchem.5b00464. Epub 2015 Oct 9.
Catalytic performance of horseradish peroxidase (HRP) electrostatically adsorbed on nanometric and semiconducting Fe-doped titanate (FT) nanosheets was successfully manipulated by visible light illumination. A colloidal solution of FT with a narrow band gap corresponding to a visible light region was fabricated through a hydrolysis reaction of metals sources. HRP could be easily bound to the FT at pH = 4 through an electrostatic interaction between them, and the formed HRP-FT was utilized for the visible-light-driven enzymatic reaction. Under exposure to visible light with enough energy for band gap excitation of the FT, catalytic activity of HRP-FT was dramatically enhanced as compared with free (unbound) HRP and was simply adjusted by light intensity. In addition, wavelength dependence of an enzymatic reaction rate was analogous to an optical absorption spectrum of the FT. These results substantiated an expected reaction mechanism in which the photoenzymatic reaction was initiated by band gap excitation of FT followed by transferring holes generated in the valence band of irradiated FT to HRP. The excited HRP oxidized substrates (amplex ultrared: AUR) accompanied by two-electron reduction to regenerate the resting state. In addition, the catalytic activity was clearly switched by turning on and off the light source.
通过可见光照射成功调控了静电吸附在纳米和半导体铁掺杂钛酸盐（FT）纳米片上的辣根过氧化物酶（HRP）的催化性能。通过金属源的水解反应制备了具有对应可见光区域窄带隙的FT胶体溶液。在pH = 4时，HRP可通过它们之间的静电相互作用轻松结合到FT上，并且所形成的HRP-FT用于可见光驱动的酶促反应。在暴露于具有足够能量用于FT带隙激发的可见光下，与游离（未结合）的HRP相比，HRP-FT的催化活性显著增强，并且可通过光强度简单调节。此外，酶促反应速率的波长依赖性类似于FT的光学吸收光谱。这些结果证实了预期的反应机制，其中光酶促反应由FT的带隙激发引发，随后将辐照FT价带中产生的空穴转移到HRP。被激发的HRP氧化底物（超红荧光素：AUR）并伴随双电子还原以再生静止状态。此外，通过打开和关闭光源可明显切换催化活性。
