Simulation Of Mononuclear Molybdenum Enzyme By Dithiolate Modified Cyclodextrin

Owning to hydrophilic exteriors and hydrophobic cavities of appropriate dimension of cyclodextrins which are similar to natural enzymes, much efforts have been paid to the area of cyclodextrin-based artificial enzymes in recent years. The chemical modification of natural cyclodextrins makes the recognition ability of cyclodextrin derivatives tunable. From the viewpoint of biomimetic synthesis, the combination of cyclodextrin (recognizing module) with molybdenum (tungsten) auxiliary factor model complexes (catalytic module), will be able to better mimic the function and physiological processes of natural enzymes.By modifying the hydroxy group on the primary rim, we indroduced dithiolate onto the main ring of β-cyclodextrin and have synthesized biomimetic complex of β-cyclodextrin which simulates natural molybdenum enzyme.And biomimetic catalysis, spatial configuration and spectroscopic properties of the target complex was investigated as well. Our results can be concentrated into two points:1. Maleonitriledithiolate modified β-Cyclodextrin:self-Inclusion and configuration-response to metal ionsThe self-inclusion of maleonitriledithiolate-modified β-cyclodextrin (mono [6-deoxy-6-(2-butene-dinitrile-2,3-dimercapto)]-β-cyclodextrin, 6-mnt-β-cyclodextrin) was studied by circular dichroism (CD) spectroscopy,’H-NMR spectroscopy, isothermal titration calorimetry (ITC), and chemical titration methods. Chemical titration experiments indicate that sodium dodecyl sulfate (SDS) is able to effectively dissociate the configuration of 6-mnt-β-cyclodextrin, as well as Cu2+ and Co2+ did in solution. The experimental data suggest that 6-mnt-β-cyclodextrin preferred self-inclusion in aqueous solution, which could be reversibly unlocked by metal ions. In its unlocked conformation,6-mnt-β-cyclodextrin is able to include Neutral Red (NR) and exhibits host-guest interactions. Upon removal of the "key" metal ion,6-mnt-β-cyclodextrin liberates the guest molecule and restores its self-inclusion.2. The simulation of molybdenum enzymes by using dithiolate modified cyclodextrin:syntheses and propertiesWe designed a new articical molybdenum enzyme by using dithiolate modified cyclodextrin. The structure of the biomimetic maleonitriledithiolate-modified β-cyclodextrin was studied by infrared spectroscopy (IR), ultraviolet and visible spectrum (UV), circular dichroism (CD),1H NMR spectroscopy, mass spectrometry (MS) and X-ray photoelectron spectroscopy (XPS). Experimental data showed that the valence of the metal center atom of the compound was + 5, which was different from the simple mixture of raw material and had certain catalytic activity. Acorrding to literatures, we selected styrene as the substrate and tested the enzyme activity of the cyclodextrin derivatives by oxidizing the styrene into benzaldehyde. The catalysis efficiency of the bionic enzyme complex was studied by changing the type of catalyst, gas chromatography (GC) and gas chromatography-mass spectrometer (GC-MS). The design of the bionic molybdenum enzyme of cyclodextrin was finished preliminary.