Crystallization of membrane proteins using photoconcentration effect by plasmon resonance

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K05291
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 30010:Crystal engineering-related
• Research Institution: Gunma University
• Principal Investigator: Tetsuo Okutsu 群馬大学, 大学院理工学府, 教授 (20261860)
• Co-Investigator(Kenkyū-buntansha): 堀内 宏明 群馬大学, 大学院理工学府, 准教授 (00334136)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 膜タンパク質 / 結晶成長 / バクテリオロドプシン / 表面プラズモン共鳴

Outline of Final Research Achievements

Crystallization of bacteriorhodopsin was performed by light-induced crystallization on gold nanostructures. The gold nanostructure was formed by gold sputtering on a glass substrate to allow gap-mode plasmon resonance to occur. In the experiment, crystals appeared when light was applied to a sample that had no crystals. The size of the crystals increased in the sample exposed to light. We considered the reason for this. Membrane proteins are adsorbed to the surface of the gold nanoparticles and diffuse over the surface. When gap-mode plasmon resonance occurs, an enhanced electric field is generated between the nanoparticles, an optical tweezers effect occurs, and surface-diffused protein molecules are trapped and concentrated in the gap. The reason why the size of the crystals increased is considered to be that the crystallized places were restricted and the crystals became larger. The results indicated light-induced crystallization of membrane proteins.

Free Research Field

物理化学　結晶工学

Academic Significance and Societal Importance of the Research Achievements

膜タンパク質は水に溶けず結晶化がきわめて難しい。今まで界面活性剤を用いて水に可溶化し塩析して結晶化する方法が提案されていたが、界面活性剤でタンパク質が変性するという問題があった。これを解決するため脂質中で結晶化する方法が提案された。本研究は脂質中での結晶化を、金のナノ構造上で膜タンパク質を吸着させプラズモン共鳴によりギャップに濃縮し結晶化させるものである。
膜タンパク質の結晶化が容易になれば、構造生物学の研究が容易に進むようになり、タンパク質の機能解明と、創薬の進歩が促進される。