Functional Analysis of Muscle Specimen by X-ray Cryomicrodiffraction Technique

介绍了在SPring-8高通量光束线BL40XU上记录微米速冻水合生物标本微衍射图的系统。该光学系统由一对在钽基体上钻孔的针孔组成，其定义孔径为直径2 μm。冷冻后的样品放置在安装在三轴测角仪上的真空冷冻室内，在液氮温度（~ -199℃）下稳定保存。在样品位置获得了1.5 μm（最大半宽）的光束尺寸。利用该系统，在相当于单个肌节（长度，~ 3 μm）的区域内，记录了昆虫飞行肌分离的单个肌原纤维（直径，~ 3 μm）的衍射图样。这项技术可能适用于其他微米大小的水合生物标本，它们比干燥的合成聚合物或生物聚合物更容易受到辐射损伤。在常规衍射记录中，生物标本的速冻也被证明有助于减少光束中的标本体积。

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.