Nanoscale Designing of Iron-Sulfur Active Center in Nitrogenase towards Nano-biomimetic Enzyme

点击翻译按钮获取中文摘要

The aim of this research has focused on the creation of nanoscale biomimetic enzyme by unveiling the function and mechanism of an iron-sulfur active center in nitrogenase enzyme. To achieve this research target, two methodologies have been developed ; (1) The production technique of organometallic and molecular clusters has been refined by laser vaporization and molecular beam in order to generate functional cluster efficiently through gas phase reactions. (2) The soft-landing method using self-assembled monolayer on a gold substrate was broadened toward various substrates, and their characteristics were evaluated by infrared reflection absorption spectroscopy (IRAS) and temperature programmed desorption spectroscopy.Functional clusters, such as organometallic cluster of vanadium-benzene, could be soft-landed efficiently onto the self-assembled monolayer on a gold substrate compared to a bare gold substrate. The adsorption state and thermal stability of V(benzene)_2 sandwich clusters soft-landed onto a self-assembled monolayer of different chain-length n-alkanethiols (C_n-SAM, n = 8, 12, 16, 18, and 22) were studied. The IRAS measurement confirmed that V(benzene)_2 clusters are molecularly adsorbed and maintain a sandwich structure on all of the SAM substrates. In addition, the clusters supported on the SAM substrates are oriented with their molecular axes tilted 70-80° off the surface normal. An Arrhenius analysis of the TPD spectra reveals that the activation energy for the desorption of the supported clusters increases linearly with the chain-length of the SAMs. For the longest chain C_<22>-SAM, the activation energy reaches around 150 kJ/mol, and the thermal desorption of the supported clusters can be considerably suppressed near room temperature, which is superior to a silicon substrate covered with hydrocarbon molecules.