EaStCHEM School of Chemistry, Joseph Black Building, The King's Buildings, Edinburgh EH9 3JJ, UK.
J Magn Reson. 2012 Oct;223:98-106. doi: 10.1016/j.jmr.2012.08.011. Epub 2012 Aug 21.
Over approximately the last 15 years the electron paramagnetic resonance (EPR) technique of double electron electron resonance (DEER) has attracted considerable attention since it allows for the precise measurement of the dipole-dipole coupling between radicals and thus can lead to distance information between pairs of radicals separated by up to ca. 8 nm. The "deadtime free" 4-pulse DEER sequence is widely used but can suffer from poor sensitivity if the electron spin-echo decays too quickly to allow collection of a sufficiently long time trace. In this paper we present a method which takes advantage of the much greater sensitivity that the 3-pulse sequence offers over the 4-pulse sequence since the measured electron spin-echo intensity (for equal sequence lengths) is greater. By combining 3- and 4-pulse DEER time traces using a method coined DEER-Stitch (DEERS) accurate dipole-dipole coupling measurements can be made which combine the sensitivity of the 3-pulse DEER sequence with the deadtime free advantage of the 4-pulse DEER sequence. To develop the DEER-Stitch method three systems were measured: a semi-rigid bis-nitroxide labeled nanowire, the bis-nitroxide labeled protein CD55 with a distance between labels of almost 8 nm and a dimeric copper amine oxidase from Arthrobacter globiformis (AGAO).
在过去大约 15 年中，电子顺磁共振（EPR）的双电子电子共振（DEER）技术引起了相当大的关注，因为它可以精确测量自由基之间的偶极-偶极耦合，从而可以提供相隔约 8nm 的成对自由基之间的距离信息。“无死时间”的 4 脉冲 DEER 序列被广泛使用，但如果电子自旋回波衰减太快，以至于无法收集足够长的时间轨迹，则灵敏度可能会很差。在本文中，我们提出了一种方法，该方法利用 3 脉冲序列比 4 脉冲序列具有更高的灵敏度，因为测量的电子自旋回波强度（对于相等的序列长度）更大。通过使用称为 DEER-Stitch（DEERS）的方法组合 3-和 4-脉冲 DEER 时间轨迹，可以进行精确的偶极-偶极耦合测量，该方法结合了 3-脉冲 DEER 序列的灵敏度和 4-脉冲 DEER 序列的无死时间优势。为了开发 DEER-Stitch 方法，测量了三个系统：半刚性双硝氧标记纳米线、标签之间距离几乎为 8nm 的双硝氧标记蛋白 CD55 和来自球形节杆菌（Arthrobacter globiformis）的二聚铜胺氧化酶（AGAO）。
