Rapid freeze-quench (RFQ) in combination with electron paramagnetic resonance (EPR) spectroscopy at X-band is a proven technique to trap and characterize paramagnetic intermediates of biochemical reactions. Preparation of suitable samples is still cumbersome, despite many attempts to remedy this problem, and limits the wide applicability of RFQ EPR. We present a method, which improves the collection of freeze-quench particles from isopentane and their packing in an EPR tube. The method is based on sucking the particle suspension into an EPR tube with a filter at the bottom. This procedure results in a significant reduction of the required volume of reactants, which allows the economical use of valuable reactants such as proteins. The approach also enables the successful collection of smaller frozen particles, which are generated at higher flow rates. The method provides for a reproducible, efficient and fast collection of the freeze-quench particles and can be easily adapted to RFQ EPR at higher microwave frequencies than X-band.

中文翻译：

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快速冷冻淬火 EPR 光谱：改进冷冻颗粒的收集

快速冷冻淬灭 (RFQ) 与 X 波段的电子顺磁共振 (EPR) 光谱相结合是一种经过验证的技术，可以捕获和表征生化反应的顺磁中间体。尽管有很多尝试来解决这个问题，但准备合适的样品仍然很麻烦，并且限制了 RFQ EPR 的广泛适用性。我们提出了一种方法，它改进了从异戊烷中收集冷冻淬火颗粒及其在 EPR 管中的包装。该方法基于将颗粒悬浮液吸入底部带有过滤器的 EPR 管中。该过程导致所需反应物体积显着减少，从而可以经济地使用有价值的反应物，例如蛋白质。该方法还能够成功收集较小的冷冻颗粒，它们是在更高的流速下产生的。该方法提供了可重复、高效和快速的冷冻淬灭颗粒收集，并且可以很容易地在比 X 波段更高的微波频率下适应 RFQ EPR。