Functional Analysis of Muscle Specimen by X-ray Cryomicrodiffraction Technique

本文介绍了在SPring-8的高通量光束线BL 40 XU上记录微米级速冻水合生物样品的显微衍射图样的系统。光学元件由一对在钽基底上钻的小孔组成，小孔直径为2 μm。将冷冻标本置于安装在三轴测角仪上的真空冷冻室中，标本稳定地保持在液氮温度（100 - 199 ℃）下。在样品位置获得1.5 μm的光束尺寸（半高宽）。利用该系统，在相当于一个肌节（长约1.3 μ m）的面积上，记录了昆虫飞行肌的一根肌原纤维（直径约1.3 μm）的衍射图。该技术可能适用于其他微米级的水合生物标本，这是更容易受到辐射损伤比干燥的合成聚合物或生物聚合物。生物样本的快速冷冻也被证明是有用的，在传统的衍射记录中减少光束中的样本体积。

The system for recording microdiffraction patterns from micrometer-sized quick-frozen hydrated biological specimens at the high-flux beamline BL40XU of SPring-8 is described. The optics consists of a pair of pinholes drilled on tantalum substratum, with a defining aperture of 2 μm in diameter. The frozen specimens are placed in an in-vacuum cryochamber mounted on a three-axis goniometer, where the specimens are stably held at a liquid-nitrogen temperature (〜-199℃). A beam size of 1.5 μm (full width at half maximum) is attained at the sample position. By using this system, diffraction patterns have been recorded from an isolated single myofibril (diameter, 〜3 μm) of an insect flight muscle in an area equivalent to a single sarcomere (length, 〜3 μm). The technique is potentially applicable to other micrometer-sized hydrated biological specimens, which are more susceptible to radiation damage than dry synthetic polymers or biopolymers. The quick-freezing of biological specimens has also been proven useful in reducing the specimen volume in the beam in conventional diffraction recordings.