Cryogen-Free Arbitrary Waveform EPR for Structural Biology and Biophysics

此次设备升级将加强大量利用电子顺磁共振（EPR）光谱的分子生物科学相关项目，并将对圣安德鲁斯大学和邓迪大学及其他大学的生物医学科学和结构生物学产生重大影响。EPR是在纳米级获得特定信息的理想方法，因为它对自由基和其他顺磁中心的磁自旋非常敏感。这些是感兴趣的，因为许多是生物化学活动的热点。最近，使用EPR的应用数量大大增加。这种增长是由新技术催化的，该技术允许研究人员选择性地将自旋引入生物分子并将其用作分子信标。自旋的磁矩与其他顺磁体或磁性核的磁矩相互作用，从而磁性地照亮其周围环境。利用自旋之间的长距离测量来绘制蛋白质构象和相互作用的轨迹变得越来越流行，就像通过灯塔的相对位置和亮度导航一样。最近，发展已经开始改变这门科学。虽然自旋通常通过开/关电磁辐射来操纵，但任意波形发生器的出现开辟了一个全新的宇宙，允许在实验中访问新的信息领域。这项技术经常被认为是EPR的未来，类似的进步已经完全改变了核磁共振领域。现在EPR更苛刻的技术要求已经得到满足，升级到这种技术似乎是合乎逻辑的，因为与初始投资相比，升级甚至意味着适度的额外成本。第二个发展涉及需要使用液氦将自旋冷却到极低的温度。氦气是一种昂贵的有限资源，已被证明极易受到供应链中断的影响，并构成相当大的安全隐患。传统上，在进行EPR实验之前，液氦将连接到光谱仪。最近，已经开发了使用闭合循环冷却的无冷冻剂低温恒温器，其操作类似于超低温冰箱。在这些低温恒温器中，使用过的氦气通过电驱动的压缩和膨胀循环冷却以重新冷却，从而被回收。这大大提高了可靠性和可持续性。重要的是，这也降低了研究人员在进行实验时的风险。此外，增加的稳定性意味着该设施可以全天候运行，并持续更长的时间，允许在给定的时间内进行更多的实验并回答更多的科学问题，圣安德鲁斯大学和邓迪大学已经利用这种方法开发了一个广泛的生物应用程序，现在正在寻求实施冷冻剂，自由任意波形EPR，以加强现有设施的项目调查生物医学的挑战和机遇，在生物基经济的未来。

This equipment upgrade will enhance a large number of molecular biosciences related projects that utilise electron paramagnetic resonance (EPR) spectroscopy and will have a major impact in the biomedical sciences and structural biology at the Universities of St Andrews and Dundee and beyond.EPR is an ideal method for obtaining specific information at the nanoscale, as it is exquisitely sensitive to the magnetic spins of radicals and other paramagnetic centres. These are of interest as many are hotspots of biochemical activity. Recently, the number of applications utilising EPR has greatly increased. This increase was catalysed by new technology which allows researchers to selectively introduce spins into biomolecules and use them as molecular beacons. The magnetic moments of the spins interact with the magnetic moments of other paramagnets or magnetic nuclei and thus magnetically illuminate their surroundings. It has become increasingly popular to use measurements of the long-range distances between the spins to map the nanoworlds of protein conformations and interactions quite as if navigating by the relative positions and brightness of lighthouses.Recently, developments have started to transform this science. While spins are commonly manipulated by on/off electromagnetic irradiation, the advent of arbitrary waveform generators has opened up a whole new universe allowing access to new realms of information in experiments. This technology is often proposed to be the future of EPR and the analogous advancements have wholly transformed the field of nuclear magnetic resonance. Now that the more demanding technical requirements of EPR are fulfilled it seems a logical imperative to upgrade to this technology as the upgrade even just means a moderate additional cost compared to the initial investment.A second development concerns the need to cool the spins to extremely low temperatures using liquid helium. Helium is an expensive, finite resource that has proven to be highly susceptible to disruption in the supply chain and poses a considerable safety hazard. Traditionally, liquid helium would be connected to the spectrometer before performing EPR experiments. Recently, cryogen-free cryostats have been developed using closed-cycle cooling that operates like an ultra-low temperature refrigerator. In these cryostats, used helium is cooled by electrically driven compression and expansion cycles to re-liquefy and thus be recycled. This greatly improves reliability and sustainability. Significantly, this also reduces risks to the researchers whilst performing experiments. Additionally, the increased stability means that the facility can operate around the clock and for a longer period of time, allowing more experiments to be performed and more scientific questions to be answered in a given time, thereby substantially improving the efficiency of the facility.The Universities of St Andrews and Dundee have developed an extensive programme of biological applications using this methodology and now seek to implement cryogen-free arbitrary waveform EPR to enhance existing facilities for projects investigating biomedical challenges and opportunities in the bio-based economy of the future.