The Study on Light-Chemical Energy Conversion of Core Duo Photocatalytic System by Fluorophores-Modified Zinc-Carboxyphenylethynyl Porphyrin (ZnPE1) Myoglobin Mutants

• Main Authors: Chang, Shih-Ying, 張世穎
• Other Authors: Wu, Tung-Kung
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/81717747656472912780

碩士 === 國立交通大學 === 分子醫學與生物工程研究所 === 100 === 　　Currently, the world’s supply of fossil fuels is being consumed at an alarming rate, and, because sunlight is plentiful, solar power has become one of the most popular areas in the development of alternative, renewable energy sources. In a previous study, an artificial, protein-based, photo-chemical, energy-conversion system, which mimicked a natural photosystem, was constructed by using ZnPP-Myoglobin/ZnPE1-Myoglobin as a photocatalyst, and the results showed that ZnPE1-MbV68L had the best catalytic velocity. During photoirradiation, the relaxation of the secondary structure caused by light and thermal energy (due to temperature increases) causes the decomposition of photoenzymes, releasing porphyrin from the heme pocket and causing the aggregation effect in the buffer solution. Consequently, the function of the photoenzymes will be lost, creating the need to improve photocatalytic velocity during the limited lifetime of the photoenzymes. 　　The strategy of using various fluorophores (i.e., I14, P28, Eosin and Texas Red) covalently conjugated to the reconstituted ZnPE1-Mb mutants because of the absorption of fluorophores can assist in extending the absorbance region, and it can be assumed that the construction of the Core Duo photocatalytic complex will improve the catalytic velocity of the conversion of light energy to chemical energy. In addition, fluorescence images of SDS-PAGE, MALDI-TOF, and UV-Vis/fluorescence spectra and circular dichroism (CD) have been used to characterize the biophysical and optic properties of the fluorophore-ZnPE1Mb mutants, which confirmed that the fluorophores and prosthetic groups have been conjugated and reconstituted successfully in the correct location in heme pocket of Mb. In addition, the redox potential of fluorophore-ZnPE1Mb mutants was confirmed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques to estimate the energy level between the fluorophores and ZnPE1, and the results showed that the Core Duo photocatalytic system functions reasonably. Next, we performed the conversion of light energy to chemical energy of NADP+ reduction utilizing different fluorophore-ZnPE1Mb mutants as the photoenzyme and photoirradiated at 352/419, 419/419, and 419/580 nm wavelengths, respectively. The energy conversion can be observed in the artificial photocatalytic system. 　　To summarize, based on the results of photocatalytic velocity, the velocity of the NADP+ reduction using suitable wavelength light for excitation of every fluorophore-ZnPE1Mbmut is approximately 30% greater than that of the system using lights of non-suitable wavelengths. Moreover, the concept of this artificial Core Duo photocatalytic system that can absorb light in the widest possible wavelength region will be realized as a potential bio-photosentizer and applied as a more efficient photocatalytic system for the development of renewable energy due, in part, to the very important information developed in this study.