Functional Analysis of Muscle Specimen by X-ray Cryomicrodiffraction Technique

本文描述了在SPRING-8的高通量光束线BL40XU上记录微米级速冻水化生物样品的显微衍射图的系统。该光学系统由一对在钽衬底上钻出的针孔组成，定义孔径为2μm。冷冻标本被放置在安装在三轴测角仪上的真空冷冻室中，在那里标本被稳定地保持在液氮温度(~-199℃)下。在样品位置获得了1.5μm的光束尺寸(半高全宽)。利用该系统，在相当于单个肌节(长度，~3μm)的面积内，记录了昆虫飞行肌肉的单个肌原纤维(直径，~3μm)的衍射图。这项技术可能适用于其他微米大小的水合生物样本，这些样本比干燥的合成聚合物或生物聚合物更容易受到辐射破坏。在传统的衍射记录中，生物样品的快速冷冻在减小光束中的样品体积方面也被证明是有用的。

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.