[22a-D315-1~6] 3.1 Basic optics and frontier of optics

▲ [22a-D315-4] Protein Assembly Formed by Cooperative Optical Trapping at Solution Surface

〇(M2)Wei-Hsiang Chiu¹, Po-Wei Yi^1,2, Roger Bresoli-Obach³, Johan Hofkens³, Eri Chatani⁴, Shuichi Toyouchi¹, Hiroshi Masuhara¹ (1.National Yang Ming Chiao Tung Univ., Taiwan, 2.NAIST, Japan, 3.KU Leuven, Belgium, 4.Kobe Univ., Japn)

Keywords:optical trapping, protein assembly, solution surface

Optical trapping is a powerful technique for manipulating nano- and microscale objects such as particles and molecules. We have been studying optical trapping of a protein, lysozyme, at the solution surface, where a highly concentrated lysozyme assembly formed and further extended to the outside of focus. This phenomenon has been considered to be one kind of “Liquid-Liquid Phase Separation (LLPS)” which is a vital process that touches various cell functions. In this work, we extended the trapping targets from single component protein solution to mixed solution by adding polyethylene glycol (PEG), which is a well-known crowding agent. The cooperative trapping behavior has been studied by applying transmission/fluorescence imaging and Raman micro-spectroscopy. A 1064 nm laser was tightly focused at the solution surface of lysozyme solution. For such relatively low concentration of lysozyme, it led to no protein assembly formation even the trapping laser irradiation over 10 min. However, by adding PEG, a protein assembly has formed under trapping laser irradiation and expanded with time at the surface of mixed solution. These results suggest that the large excluded volume of PEG as a crowding agent modifies lysozyme protein-protein interaction.