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*This article was first published on the "Nanoenzymes" public account, January 12, 2021
*Editor: Yu Jiyuan
Hello everyone, today I want to share with you the article Photo-Controllable Catalysis and Chiral Monosaccharide Recognition Induced by Cyclodextrin Derivatives published by the Supramolecular Chemistry Research Group of Professor Liu Yu of Nankai University on January 5, 2021 in Angwandte Chemie. This paper creatively constructs a photoreactive supramolecular catalytic system composed of polycationic α-cyclodextrin (6-Iz-α-CD) and gold nanoparticles (AuNP). (Figure 1)
Figure 1. Light-controlled AuNP@6-Iz-α-CD catalytic activity and chirality identification catalytic process
Citric acid-modified AuNP has good glucosoid oxidase (GOx) activity, which can catalyze the oxidation of glucose into gluconic acid while producing H2O2, which in turn measures glucose content by catalyzing the color development reaction of H2O2 with TMB. The catalytic reaction of AuNP oxidation of glucose sugar is similar to that of GOx, and the reaction formula is shown in the following formula:
Therefore, AuNP is regarded as a mimetic enzyme of glucose oxidase, which is characterized by high catalytic activity, good stability, low cost, and can regulate enzyme activity by controlling size and surface modification. However, AuNP also has problems such as poor substrate selectivity. To this end, the work explored the development of a selectively catalytic AuNP.
AuNP and 6-Iz-α-CD constructed a supramolecular catalytic system by non-covalent interaction AuNP@6-Iz-α-CD (Figure 2), which was tested to have glucose-like oxidase activity, and the cavity of 6-Iz-α-CD can identify chiral monosaccharide molecules, thereby achieving selective catalysis of glucose of different chiral properties (Figure 3, Figure 4). In this process, the substrate needs to enter the cavity, so that the aldehyde group is oxidized into an acid by a reaction of cyclodextrin contact with AuNP. Since the sodium D-gluconate generated by the reaction has a high bond with the 6-Iz-α-CD cavity and the positive charge adsorption hinders its separation, D-glucose cannot enter the cavity to participate in the reaction, and the reaction is terminated. The affinity of sodium L-gluconate with the 6-Iz-α-CD cavity is very weak and does not prevent L-glucose from continuing to respond.
Figure 2. (a) Add SPR of AuNP with different concentrations of 6-Iz-α-CD. (b) Ζ potential α of AuNP at different concentrations ([Au] = 7.96×10-4 g/L, [6-Iz-α-CD] = 0 to 1.8×10-4 M) at different concentrations of AuNP. (c) DLS analysis of AuNP@6-Iz-α-CD in aqueous solution. (d) Fourier transform infrared spectra of 6-Iz-α-CD and AuNP@6-Iz-α-CD.
Figure 3. (a) (b) AuNP@6-Iz-α-CD catalyze substrates of different concentrations and chiralities. (c) (d) AuNP@6-Iz-α-CD catalyze substrates of varying lengths and different chiralities. (e) (f) Simulate the catalytic process of different chiral monosaccharide assemblies.
Figure 4. AuNP@6-Iz-α-CD for rapid color recognition of different chiral monosaccharides
In addition, the work introduced light-responsive azobenzene-modified diphenylalanine (Azo-FF) as a guest molecule to control the catalytic activity of supramolecular systems. The affinity of Azo-FF with the cyclodextrin cavity is affected by irradiation. After visible light irradiation at 450 nm, the affinity of the catalyst became higher, azobenzene competitively entered the cyclodextrin cavity, hindering chiral monosaccharides from entering the cavity to bind to the substrate, diphenylalanine reduced the catalytic activity of AuNP aggregation, and Azo-FF formed a fiber network to separate AuNP@6-Iz-α-CD from the solution. This process is reversible and when irradiated with UV AuNP@6-Iz-α-CD catalytically recovered. Therefore, the catalytic activity of AuNP@6-Izα-CD can be regulated by changing irradiation. (Figure 5)
Figure 5. Catalysts were taken as (a)AuNP, (b) AuNP@6-Izα-CD([Au] = 7.96×10-4 g/L, [6-Iz-α-CD] = 4×10-5 M, [4-NP] = 5×10-5 to 3×10-4 M) and (c) AuNP@6-Iz-α-CD + Azo-FF([Azo-FF] = 0 to 8×10-5 M, [4-NP] = 1×10-4 M), respectively, to catalyze 4-NP reduction. (d) Changes in ultraviolet absorption of AuNP @6-Iz-α-CD with different equivalents of Azo-FF. (e) Observation of the morphology of AuNP@6-Iz-α-CD + Azo-FF by TEM and (f) SEM.
In summary, this paper develops a light-controlled supramolecular catalytic system. AuNP@6-Iz-α-CD has a special glucose-like oxidase activity, which can identify catalytic oxidation of chiral monosaccharides and regulate its catalytic activity with light-responsive Azo-FF as the object molecule, which is a creative work in the catalysis of AuNP enzyme activity and the intelligent response of supramolecular systems.
Original link:
https://onlinelibrary.wiley.com/doi/epdf/10.1002/anie.202017001
Written by: Wang Yuting
Reviewer: Li Sirong, Xu Gengchen
Editor: Xu Gengchen