[16a-414-1~9] 12.1 Fabrications and Structure Controls

[16a-414-4] Real-time observation of knetics in absorption onto gas-water interface of ferritin molecules by Quasi Elastic Laser Scattering method

〇Yuji Fujita¹, Ken-ichi Sano¹, Ikezoe Yasuhiro¹ (1.Nippon Institute of Technology)

Keywords:Ferittin, water surface, surface tension

Two-dimensional (2D) crystals formed by nanometer-sized materials are of interest in a wide variety of fields, such as nanoelectronics or dynamic process of self-assembly. Since a protein molecule has identical structure, it becomes an excellent building block for the self-assembly. In particular, the ferritin, which is a ubiquitous protein molecule among living species, has been paid attention due to its unique molecular structure; it is a quasi-spherical hollow shell structure (12 nm outer diameter and 7 nm inner diameter) composed of 24 subunits (∼450 kDa). The molecular cavity of ferritin is capable of storing various inorganic materials such as metal complexes, magnetic materials, and photoresponsive semiconductors. Therefore, the ferritin is expected to make a contribution to diverse applications. So far, there have been many researches on the fabrication of two-dimensional crystal-like molecular film of ferritin on water surface, however, the kinetic process has not been fully understood. Analysis of the scanning electron microscope (SEM) images of the crystals on a molecular scale allows us to know how the protein molecules assembled into a crystal, however, the SEM images do not tell us directly the kinetic process of the crystallization although we are able to discuss the process by analyzing the alignment of molecules. In order to know the process in detail, it is important to investigate the kinetics by an in situ observation technique. In this study, we have developed a non-contact surface tension measurement system by the Quasi Elastic Laser Scattering (QELS) method, and successfully obtained the time course of the surface tension of water during the adsorption process of ferritin. The ferritin we used here is a genetically engineered ferritin, N1-LF, which has a small hydrophobic peptide on the molecular surface. The experimental result shows us that it takes several hours for the ferritin to cover the whole water surface area, and interestingly the viscosity of the water surface keeps changing through the adsorption process, which suggests the formation of molecular film on the water surface by the self-assembly of molecules.