Nanostructures Electrochemistry And Spectroscopy Study Of The Impact Of Protein Conformation

Nanomaterials are considered to have the potential applications in biology including bioseparation, molecular diagnostics, drug delivery, drug target, and so on. However, these applications significantly depend on the biosafety of the nanomaterials. Thus, the biosafety research of nanomaterials will provide a basis and guarantee for its further biological applications. As the significant material basis of life activities, protein plays an important role in all life activities. The alteration in the conformational structure of protein will not only affect the performance of its biological functions, but also lead to protein-mediated diseases such as Alzheimer’s disease, Parkinson’s disease, amyloid disease, and so on. We choose study the effects of nanomaterials on the conformational structure of protein here. In this paper, we chose hemoglobin (Hb) and glucose oxidase (GOx) as the research object, and studied the conformational structure changes of Hb induced by gold nanoparticles (AuNPs) and that of GOx induced by graphene oxide GO, respectively, in detail by a combination of electrochemical method, ultraviolet—visible (UV-vis) spectroscopy, fluorescence, circular dichroism (CD), and Fourier transform infrared (FTIR) spectroscopy. The results obtained here not only provide the detailed conformational behavior of molecules on nanomaterials and a theoretical basis for the biofunctionalized application of protein, but also create a framework for analyzing the biosafety of nanomaterials in terms of the biological behavior of biomacromolecules, in order to direct the further applications of the nanomaterials. The main conclusions obtained in this paper are as follows:1. Study the conformational structure changes of Hb induced by AuNPs. In this study, the conformational structure changes of Hb induced by AuNPs were studied in detail by a combination of electrochemical method, ultraviolet—visible spectroscopy, fluorescence, circular dichroism, and Fourier transform infrared spectroscopy. The electrochemical results indicated that the native conformational structure of Hb changed after conjugating with AuNPs, which could result in the exposure of the heme center from the hydrophobic pockets and thus lead to the enhancement in electron transfer rate. The spectroscopic results indicated that AuNPs could result a disturbance of the secondary structure of Hb and induce the exposure of the heme group and tryptophan (Trp) residues to the solvent, leading to the conversion of α-helix to β-sheet structures and unfolding of Hb. Moreover, we studied the influence of AuNPs with different particle size on the conformation of Hb. The results indicated that the smaller particle size of AuNPs is, the greater the conformation of Hb changes.2. The effects of GO on the conformational structure and activity of GOx. In this study, the conformational structure changes of GOx induced by GO were studied in detail by ultraviolet-visible spectroscopy, fluorescence, circular dichroism, and Fourier transform infrared spectroscopy. The spectroscopic results indicated that GOx underwent substantial conformational changes both at secondary and tertiary structure level after assembling with GO. GO could induce the exposure of the FAD active center (flavin adenine dinucleotide) moiety to solvent and Trp residues to a more hydrophobic environment, and lead conversion of α-helix to β-sheet structures, even unfolding of GOx. The catalytic activity evaluation of GOx showed that the activity of GOx decreased significantly with the increase of the GO concentration. The possible reasons of these conformational structure changes of GOx were also discussed.