Lack of controls and understanding in nucleation, which proceeds crystal growth and other phase transitions, has been a bottleneck challenge in chemistry, materials, biology, and other fields. The exemplary needs for better methods for biomacromolecule crystallization include (1) synthesizing crystals for high-resolution structure determinations in fundamental research and (2) tuning the crystal habit and thus the corresponding properties in materials and pharmaceutical applications. Herein, a deterministic method is established capable of sustaining the nucleation and growth of a single crystal using the protein lysozyme as a prototype. The supersaturation is localized at the interface between a sample and a precipitant solution, spatially confined by the tip of a single nanopipette. The exchange of matter between the two solutions determines the supersaturation, which is controlled by electrokinetic ion transport driven by an external potential waveform. Nucleation and subsequent crystal growth disrupt the ionic current limited by the nanotip and are detected. The nucleation and growth of individual single crystals are measured in real time. Electroanalytical and optical signatures are elucidated as feedbacks with which active controls in crystal quality and method consistency are achieved: five out of five crystals diffract at a true atomic resolution of up to 1.2 Å. As controls, those synthesized under less optimized conditions diffract poorly. The crystal habits during the growth process are tuned successfully by adjusting the flux. The universal mechanism of nano-transport kinetics, together with the correlations of the diffraction quality and crystal habit with the crystallization control parameters, lay the foundation for the generalization to other materials systems.

中文翻译：

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主动控制成核和高质量蛋白质晶体合成的单实体方法

对进行晶体生长和其他相变的成核缺乏控制和理解一直是化学、材料、生物学和其他领域的瓶颈挑战。对更好的生物大分子结晶方法的典型需求包括（1）在基础研究中合成用于高分辨率结构测定的晶体，以及（2）调整晶体习性，从而调整材料和药物应用中的相应特性。在此，建立了一种确定性方法，能够使用蛋白质溶菌酶作为原型维持单晶的成核和生长。过饱和度位于样品和沉淀剂溶液之间的界面处，在空间上受到单个纳米移液管尖端的限制。两种溶液之间的物质交换决定了过饱和度，过饱和度由外部电势波形驱动的动电离子传输控制。成核和随后的晶体生长破坏了纳米尖端限制的离子电流并被检测到。实时测量单个单晶的成核和生长。电分析和光学特征被阐明为反馈，通过反馈可以实现晶体质量和方法一致性的主动控制：五分之五的晶体以高达 1.2 Å 的真实原子分辨率进行衍射。作为对照，在不太优化的条件下合成的那些衍射性能很差。通过调节通量成功地调节了生长过程中的晶体习性。纳米传输动力学的普遍机制，