發展同調X光散射影像實驗在生物樣品結構之研究

Abstract

過去五年來，新一族同步輻射加速器開始加入運轉，其低束散度(low emittance)的特質， 使利用同調性(coherence)的X 光實驗開始受到極大的注意，未來幾年，美、日、德等國 之自由電子雷射(free electron laser)更將達到硬X 光的波段，也開始開啟百年來無法解決 的X 光相位(phase)實驗。此完全同調的X 光光源使X 光結構研究不再侷限於有序(order) 的晶體條件下。本計畫主旨在發展X 光相位相關的影像及散射技術，同時應用在獲取尚 未解析的二個生物結構: (1) 雙主體蛋白質 (NOS) 用來管控神經訊號傳遞; (2) 脂質基 因載體(Lipid gene-carriers) 及其在細胞內的傳遞路徑。 表

The availabilities of bright x-ray sources from synchrotron undulators and, most importantly, the new x-ray free electron lasers allow to explore x-ray diffuse scattering measurements by the utilization of coherent x-rays. In couple with the new developments in x-ray imaging theories, such as over sampling methods of phase problem and iterative phase retrieve methods for phase imaging, have opened up exciting opportunities in x-ray science to solve the long standing structural problems of disordered or partially disordered systems in condensed matter and biology. In this proposal, special efforts will be focused on the implementation of x-ray Coherent Diffractive Imaging (CDI) for the studies of biological systems. Specific cases have been identified which include cells and protein complex. The work of this proposal is discussed in three parts: (1) Implementation of zone-plate based CDI instrumentation at SPring-8, Japan, (2) SAXS and CDI studies of the structure of soft systems, e.g. a two-domain protein complex Nitric Oxide Synthases (NOS), and (3) 3D imaging of lipid gene-carriers interacting with mammalian cells by TXM and CDI.