Tomizaki Kin-Ya, Yamaguchi Yuichi, Tsukamoto Naoyuki, Imai Takahito
Department of Materials Chemistry, Ryukoku University, Seta, 520-2194 Otsu, Japan.
Innovative Materials and Processing Research Center, Ryukoku University, Seta, 520-2194 Otsu, Japan.
Protein Pept Lett. 2018;25(1):56-63. doi: 10.2174/0929866525666171214113324.
Gold nanoparticles are promising nanomaterials for catalytic reactions, sensing/imaging systems, photonic/plasmonic devices, and electronics because of their unique physical and chemical properties. To date, significant catalytic activities of gold nanoparticles have been reported for reactions such as carbon monooxide oxidation and 4-nitrophenol reduction, and diverse gold nanoparticle morphologies such as nanospheres, wires, rods, and cubes have been achieved using a variety of capping/stabilizing organic molecules. However, there are few reports on the simultaneous assembly of peptides forming secondary structures and metallic nanoparticles into peptide-metallic particle hybrids under mild aqueous conditions and demonstration of their use as catalysts. Furthermore, the gold nanoribbon surfaces are covered with β-sheet structures, disrupting the access of substrates to the active sites, thereby possibly inhibiting their catalytic activity.
The main objective of this study is design, synthesis, and characterization of peptidegold nanoparticle hybrids that are prepared by an α-helical conformation of a template and examination of the catalytic activities of the hybrids.
We here report (i) the design, synthesis, and characterization of a new template peptide, RU025, that tends to form an α-helical conformation and self-assembles into network nanoarchitectures in aqueous solution through possibly hydrophobic and electrostatic interactions, (ii) the characterization of gold seed crystals synthesized by mixing RU025 and HAuCl4, (iii) the characterization of peptide-gold nanoparticle hybrids directed by crystal growth with NaBH4 and the dependence on the conditions used for nucleation, and (iv) the catalytic activities of the hybrids towards the reduction of 4-nitrophenol to 4-aminophenol in the presence of excess NaBH4.
We demonstrated the design, synthesis, and characterization of a new template peptide, RU025, that tends to form an α-helical conformation and self-assembles into network nanoarchitectures in aqueous solution. Gold seed crystals were synthesized by mixing RU025 and HAuCl4 in a 1:2 molar ratio, followed by further reduction of the gold seed crystals with NaBH4. This reaction afforded worm-like gold nanoparticles embedded in the peptide self-assemblies. The peptide-gold nanoparticle hybrids exhibited catalytic activities for the Langmuir-Hinshelwood type reduction of 4-nitrophenol to 4-aminophenol in the presence of excess NaBH4, with an activation energy of 33 kJ mol-1.
The size and morphology of gold nanoparticles can be tuned in the nanometer range by altering the peptide concentration relative to HAuCl4 and by changing the nucleation time. This method for constructing peptide-metallic nanoparticle hybrids, in which metallic nanoparticles are dispersed in the peptide self-assemblies, provides highly reactive catalysts.
由于其独特的物理和化学性质，金纳米颗粒是用于催化反应、传感/成像系统、光子/等离子体器件及电子产品的有前景的纳米材料。迄今为止，已报道金纳米颗粒对一氧化碳氧化和4-硝基苯酚还原等反应具有显著的催化活性，并且使用各种封端/稳定有机分子已实现了多种金纳米颗粒形态，如纳米球、纳米线、纳米棒和纳米立方体。然而，关于在温和的水性条件下将形成二级结构的肽与金属纳米颗粒同时组装成肽-金属颗粒杂化物并证明其作为催化剂的用途的报道很少。此外，金纳米带表面覆盖有β-折叠结构，这会干扰底物进入活性位点，从而可能抑制其催化活性。
本研究的主要目的是设计、合成和表征通过模板的α-螺旋构象制备的肽-金纳米颗粒杂化物，并研究该杂化物的催化活性。
我们在此报告（i）一种新的模板肽RU025的设计、合成和表征，该肽倾向于形成α-螺旋构象，并通过可能的疏水和静电相互作用在水溶液中自组装成网络纳米结构；（ii）通过混合RU025和HAuCl4合成的金晶种的表征；（iii）用NaBH4通过晶体生长引导的肽-金纳米颗粒杂化物的表征以及对成核所用条件的依赖性；（iv）在过量NaBH4存在下，该杂化物对4-硝基苯酚还原为4-氨基苯酚的催化活性。
我们证明了一种新的模板肽RU025的设计、合成和表征，该肽倾向于形成α-螺旋构象，并在水溶液中自组装成网络纳米结构。通过以1:2的摩尔比混合RU025和HAuCl4合成金晶种，然后用NaBH4进一步还原金晶种。该反应得到嵌入肽自组装体中的蠕虫状金纳米颗粒。在过量NaBH4存在下，肽-金纳米颗粒杂化物对4-硝基苯酚还原为4-氨基苯酚的Langmuir-Hinshelwood型反应表现出催化活性，活化能为33 kJ mol-1。
通过改变相对于HAuCl4的肽浓度和改变成核时间，可以在纳米范围内调节金纳米颗粒的尺寸和形态。这种构建肽-金属纳米颗粒杂化物的方法，其中金属纳米颗粒分散在肽自组装体中，提供了高活性催化剂。
