The Preparation Of Molecular Assembled Systems With Histidine Or Benzimidazole And Their Actions Toward Superoxide Anion

Biosensors can be fabricated through fixing the biologically active species (such as enzyme, antibody, cell etc.) to the surface of electrode by surface self-assembly monolayers (SAMs) technology. Their potential applications in the fields of chemistry, biology, clinic diagnestics as well as environmental monitoring have been proved. Superoxide dismutase (SOD) is a common metalloenzyme in organism. However, the direct ultilization of natural SOD have many problems such as stability, affinity with biological film, bioavailability and antigenic property etc. The model compounds of superoxide dismutase with the related stucture have low molecular weight, high stability, relatively long half-time and good solubility in liposome. All these can overcome the limitation of natural SOD for actual application. Up to now much attention has been paid to the electrochemical studies on electron transfer of SOD, because it has been recognized that information on direct electron transfer is very useful in understanding the intrinsic thermodynamic and kinetic properties of SOD. Constructing MSOD SAMs system or immobilizing MSOD on gold electrode provides direct electrochemical method for the investigation of SOD simulation.In our work, we synthesized histidine derivatives. Construct MSOD system which contains histidine derivatives with self-assembly ability and immobilize two kinds of MIDB(CuIDB, MnIDB) on gold electrodes. The strcture and the property of these modified elctrodes was studied by electrochemical methods. SOD-like activity of these modified elctrodes towardes superoxide was measured. The main contents are listed as the following:1. 11,11' -dithioldi(N(α)-Boc-N(im)-benzyl-L-histidylundecanoate) (BBDTH), 11,11 ' -dithioldi(N(im)-benzyl-L-histidylundecanoate) (BDTH) 11,11'-dithioldi (L-histidylundecanoate) (DTH) were synthesized. The molecular structures of theintermediates and the target compounds were confirmed by ¹H NMR, GC-MS and LC-MS etc.2. BBDTH/Au SAMs and BBDTH/HT/Au mixed SAMs (the first kind); BDTH/Au SAMs and BDTH/HT/Au mixed SAMs (the second kind); DTH/Au SAMs and DTH/HT/Au mixed SAMs (the third kind) was prepared by self-assembly monolayer technology. The electrochemical cyclic voltammetry and electrochemical impendence spectra were employed to characterize the structure and the property of the above three kinds (six types) SAMs on gold. The results shows that closely packed and well ordered SAMs have been fabricated and their surface coverage is over 99.9%. For the SAMs which belong to the same kind, the coverage is higher than the single SAMs. For the mixed SAMs which belongs to the same kind, the coverage increases with the more ratio of HT. At the same time, for the SAMs which belong to the same type, the coverage increases with the less number of protection group.3. Copper ion was coordinated to the surface of the above-mentioned SAMs systems. The results shows that the amount of coordinated Cu²⁺ decreases with the increase of the ratio of HT for the first and the second kind of modified electrodes. No obvious rule was found for the third kinds of modified electrodes. The amount of coordinated Cu²⁺ increases with the less number of protection group for the same type of modified electrodes.4. MIDB (CuIDB, MnIDB) were linked to the surface of MPA/Au SAMs by use of DCC as coupling reagent. The electrochemical cyclic voltammetry and electrochemical impendence spectra were employed to characterize the structure of the modified electrode, and the result shows that Cu (Mn) IDB was adsorbed on the electrode by chemical adsoption. Cyclic voltammetry has been employed to investigate the electrochemical reduction-oxidation of the SAMs modified electrodes, and the result shows Cu (Mn) IDB possess the redox activity.5. Xanthine-XOD was employed as the generation system of O₂^-, then cyclic voltammetry was employed to investigate the SOD-Iike activity of MIDB/MPA/AuDTH/HT/Cu²⁺/Au and DTH/Mn²⁺( Zn²⁺)/Au modified electrode. The results shows that these modifi...