Protein crystallization induced by poly(ethylene) glycol : A small angle x-ray scattering study(Poster session 1, New Frontiers in Colloidal Physics : A Bridge between Micro- and Macroscopic Concepts in Soft Matter)

Abstract

この論文は国立情報学研究所の電子図書館事業により電子化されました。水溶性高分子が球状タンパク質分子間にどのような相互作用をどのようなメカニズムで誘起するのかを知ることは、タンパク質溶液の制御(安定化や結晶化など)のために重要である。また、通常電荷を持ち、静電的に安定化しているタンパク質溶液の構造を、電荷を持たない水溶性の高分子が不安定化するメカニズムはソフトマターの液体構造という視点からも興味深い。本研究では、モデルタンパク質として直径約8nmのグルコースイソメラーゼを用い、水溶性高分子ポリエチレングリコールが誘起するタンパク質の溶液構造変化を、X線小角散乱法によって測定した。Proteins in aqueous solutions usually have surface charges which stabilize the solution. By adding salt or changing pH of the solution to decrease the electrostatic stabilization induces the molecular aggregation. On the other hand, it is well known that water-soluble polymers such as polyethylene glycol can destabilize protein solutions. Since these polymers often do not have any charges, it is believed that the primary mechanism of the destabilization is the depletion attraction at so-called protein limit, where the size of polymers is much larger than that of proteins. The real situation is, however, far more complicated than the model in theories. For example, the size of typical proteins (a few nanometers) is more or less similar to that of polymers frequently used for protein solutions. Moreover, as mentioned above, proteins have charges, which can a ect the depletion interaction. Croze and Cates suggested that there is a nonadditive property between the electrostatic interaction and the depletion interaction. Our aim of this study, therefore, is to give experimental information on the structure of protein solutions with polymers while controlling the electrostatic interactions with added salt