Artificial Enzyme Based On Host-guest Interaction On Surface Of Gold Nanoparticles And Its Properties

As macromolecular biocatalysts,natural enzymes are essential substances for human metabolism.In various catalytic systems,the excellent catalytic activity of natural enzymes has attracted great attention.However,the inherent instability and complexity of natural enzymes hinder their further development and wider application.Therefore,developing artificial enzymes is extremely important.In this thesis,we design and synthesize polypeptide-based and organometallic photo-modulation artificial enzymes by using cyclodextrins capped gold nanoparticles(AuNP@CDs)as scaffolds through hostguest interaction.These artificial enzymes show excellent catalytic performance.Specific researches are as follows:1.The β-cyclodextrins functionalized gold nanoparticles(AuNP@CDs)with an average diameter of approximately 2.6 nm are designed and synthesized,and their sucessful preparation is proved by various characterization.AuNP@CDs have excellent catalytic capacity for 4-nitrophenol(4-NP),which provides the possibility for cascade catalysis of artificial enzymes.2.Using AuNP@CDs as a scaffold,three kinds of azobenzene modified polypeptides are self-assembled to form peptide-based artificial enzymes(AuNP@CDs-Azo-peptide)through host-guest interaction.The AuNP@CDs-Azo-peptide has hydrolase-like activity,and the positions of imidazole groups on the three types of peptides lead to the different catalytic performance of artificial enzymes.Due to the photoisomerization of azobenzene,AuNP@CDs-Azo-peptide disassembles/assembles under UV/visible light irradiation.AuNP@CDs-Azo-peptide catalyzes the hydrolysis of 4-nitrophenyl acetate(4-NPA)to4-NP,and AuNP@CDs catalyzes the reduction of 4-NP to 4-nitroaniline(4-AP).Therefore,it is expected to realize photo-controlled cascade catalysis.This study provides an interesting strategy for regulating the catalytic activity of peptide-based photomodulated simulated enzymes.3.Using AuNP@CDs as a support,the surface of azobenzene modified triethylenetetramine(Azo-N4)is anchored by host-guest interaction,followed by Zn(II)coordination to form organometallics monolayer to construct a photo-modulated organometallic artificial enzymes.The catalytic site of the artificial enzymes is derived from the outer organometallic layer.The catalytic site derives from the outer organometallic layer.The artificial enzymes can catalyze the hydrolysis of 4-NPA to 4-NP and detect Zn(II)by catalytic signal.Due to the photoisomerization of azobenzene,the supramolecular assembly of host-guest interaction is reversibly modulated by light.The reversible assembly leads to activity modulation and cascade catalysis of AuNP@CDs-Azo-N4-Zn as well as the recovery of AuNP@CDs.This study provides a new idea and reference for the rational design and activity regulation of organometallic artificial enzymes.