Beyerlein K R, Adriano L, Heymann M, Kirian R, Knoška J, Wilde F, Chapman H N, Bajt S
Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron, Notkestraβe 85, 22607 Hamburg, Germany.
Photon Science, Deutsches Elektronen-Synchrotron, Notkestraβe 85, 22607 Hamburg, Germany.
Rev Sci Instrum. 2015 Dec;86(12):125104. doi: 10.1063/1.4936843.
Serial femtosecond crystallography (SFX) using X-ray Free-Electron Lasers (XFELs) allows for room temperature protein structure determination without evidence of conventional radiation damage. In this method, a liquid suspension of protein microcrystals can be delivered to the X-ray beam in vacuum as a micro-jet, which replenishes the crystals at a rate that exceeds the current XFEL pulse repetition rate. Gas dynamic virtual nozzles produce the required micrometer-sized streams by the focusing action of a coaxial sheath gas and have been shown to be effective for SFX experiments. Here, we describe the design and characterization of such nozzles assembled from ceramic micro-injection molded outer gas-focusing capillaries. Trends of the emitted jet diameter and jet length as a function of supplied liquid and gas flow rates are measured by a fast imaging system. The observed trends are explained by derived relationships considering choked gas flow and liquid flow conservation. Finally, the performance of these nozzles in a SFX experiment is presented, including an analysis of the observed background.
使用X射线自由电子激光（XFEL）的串行飞秒晶体学（SFX）能够在室温下确定蛋白质结构，且不存在传统辐射损伤的迹象。在这种方法中，蛋白质微晶的液体悬浮液可以在真空中作为微射流输送到X射线束中，其补充晶体的速率超过了当前XFEL脉冲重复率。气体动力学虚拟喷嘴通过同轴鞘气的聚焦作用产生所需的微米级流，并且已被证明对SFX实验有效。在这里，我们描述了由陶瓷微注塑成型的外部气体聚焦毛细管组装而成的此类喷嘴的设计和特性。通过快速成像系统测量发射射流直径和射流长度随供应的液体和气体流速的变化趋势。考虑到阻塞气流和液体流量守恒，通过推导关系来解释观察到的趋势。最后，展示了这些喷嘴在SFX实验中的性能，包括对观察到的背景的分析。
