Study About The Effects Of Nano-sized Aluminum Compounds On Coenzymes And Related Dehydrogenases Activity

In recent years, the potential effects of nanoparticles, which cause unforeseen health or environmental hazards to human beings or other animal species, have attracted considerable concerns in the whole world. The interaction between nano-sized aluminum compounds and organics may change the properties of the organism, therefore, nano-aluminum compounds are considered as potential environmental pollutants. Under physiological conditions of biological systems, nano-sized oxides and hydroxides may be the exact species of aluminum. In this study, nano-sized aluminum compounds were synthesized and the adsorption of adenine dinucleotide (NAD+) and adenine dinucleotide phosphate (NADP+) on the synthesis nanoparticles were investigated. The experiments involved the adsorption mechanism and the impact on the biological systems. Meanwhile, electrochemical methods were performed to study the effect of different species of aluminum compounds on the activity of NAD(H)/NADP(H)-dependent dehydrogenases. The fluorescence and circular dichroism spectroscopy were applied to interpret the proposed mechanism. The main results can be concluded as follows:1. Nano-sized α-Al2O3, γ-Al2O3and y-AlOOH were synthesized. And the adsorption behavior of NAD+on crystallized nano-sized γ-AlOOH,γ-Al2O3and α-Al2O3were investigated by using batch adsorption experiments and modern analytical methods. The methods included UV-vis, ICP, XRD, TG-DTA, XPS, ATR-FTIR and fluorescence spectroscopy over a range of different NAD+/NADP+concentrations, pH conditions and ionic strength conditions. The results showed that the adsorption capacity exhibited a strong dependence on pH values, that is, the amount of adsorbed coenzymes decreased as the pH values increased. Moreover, the facts indicated that the ligand adsorption also depended on the concentration of ionic-strength, which is the typical property of outer-sphere complex fashion. All observations suggested that NAD+on α-Al2O3and γ-AlOOH were predominantly adsorbed in outer-sphere mode. While in situ ATR-FTIR and XPS spectra of adsorbed NAD+indicated that there was some minor inner-sphere mode coupled with the outer-sphere coating on γ-Al2O3surface. Under the experimental conditions, the conformation of NAD+/NADP+changed with the addition of nanoparticles.2. The adsorption behavior of NADP+on nano-sized γ-AlOOH, γ-Al2O3and α-Al2O3were studied by using modern analytical methods. The results showed that the adsorption capacity exhibited a strong dependence on pH values. As3<pH value<5, the amount of adsorbed NADP+was lower than previously expected, due to the competition of solution-based Al(Ⅲ). All observations suggested that NADP+on α-Al2O3and y-AlOOH were predominantly adsorbed in outer-sphere fashions. While in situ ATR-FTIR and TG spectra indicated that there was some minor inner-sphere mode coupled with the outer-sphere complex on y-Al2O3surface. Under the experimental conditions, the conformation of NAD+/NADP+changed with the addition of nanoparticles. The results showed the bioavailability of NAD(H)/NADP(H)-dependent dehydrogenase can be influenced with the addition of nanoparticles.3. The research of the multi-wall carbon nanotube and graphene modified electrode were studied with the influence of Al(III) and Al13on the activity of the NAD(H)/NADP(H)-dependent dehydrogenases in solutions. The CRG/CHIT modified electrode was prepared and used to monitor the amperometric response of NADH and NADPH, which was applied to detect the activity of alcohol dehydrogenase (ADH) and glutathione reductase (GR). It was found that not only over potential of NADH/NADPH on the bare glassy carbon electrode was reduced, but also nano-sized Al2O3and AlOOH had been identically determined to display inhibition on activity of GR and ADH. According to Lineweaver Burk double reciprocal plot, the values of Michaelis constant Km for related dehydrogenases were calculated under different concentrations of nano-sized Al2O3and AlOOH added to the system. The properties of Km and Vmax indicated that the roles of nano-sized Al2O3and AlOOH in the ADH and GR catalytical system were ascribed as anti-competitive inhibitors. Moreover, fluorescence spectroscopy and circular dichroism (CD) spectra were applied to reveal the fact that nano-sized Al2O3and AlOOH could induce the conformational changes of both coenzymes and the related dehydrogenases, and then the unfavorable structural changes of substrate and enzyme would induce the change of enzyme activity. In a word, the results proved that the amperometric i-t curve could be applied as an effective tool to monitor the enzyme activity in the biological system due to its perfect property of stability, sensitivity and easy operation.