Sakellariou D, Le Goff G, Jacquinot J-F
Laboratoire de Structure et Dynamique par Résonance Magnétique, Service de Chimie Moléculaire (Laboratoire Claude Fréjacques, CNRS URA 331) DSM/DRECAM/SCM, CEA Saclay, Gif-sur-Yvette 91191, France.
Nature. 2007 Jun 7;447(7145):694-7. doi: 10.1038/nature05897.
Nuclear magnetic resonance (NMR) can probe the local structure and dynamic properties of liquids and solids, making it one of the most powerful and versatile analytical methods available today. However, its intrinsically low sensitivity precludes NMR analysis of very small samples-as frequently used when studying isotopically labelled biological molecules or advanced materials, or as preferred when conducting high-throughput screening of biological samples or 'lab-on-a-chip' studies. The sensitivity of NMR has been improved by using static micro-coils, alternative detection schemes and pre-polarization approaches. But these strategies cannot be easily used in NMR experiments involving the fast sample spinning essential for obtaining well-resolved spectra from non-liquid samples. Here we demonstrate that inductive coupling allows wireless transmission of radio-frequency pulses and the reception of NMR signals under fast spinning of both detector coil and sample. This enables NMR measurements characterized by an optimal filling factor, very high radio-frequency field amplitudes and enhanced sensitivity that increases with decreasing sample volume. Signals obtained for nanolitre-sized samples of organic powders and biological tissue increase by almost one order of magnitude (or, equivalently, are acquired two orders of magnitude faster), compared to standard NMR measurements. Our approach also offers optimal sensitivity when studying samples that need to be confined inside multiple safety barriers, such as radioactive materials. In principle, the co-rotation of a micrometre-sized detector coil with the sample and the use of inductive coupling (techniques that are at the heart of our method) should enable highly sensitive NMR measurements on any mass-limited sample that requires fast mechanical rotation to obtain well-resolved spectra. The method is easy to implement on a commercial NMR set-up and exhibits improved performance with miniaturization, and we accordingly expect that it will facilitate the development of novel solid-state NMR methodologies and find wide use in high-throughput chemical and biomedical analysis.
核磁共振（NMR）能够探测液体和固体的局部结构及动态特性，使其成为当今最强大且用途广泛的分析方法之一。然而，其固有的低灵敏度使得NMR无法对非常小的样品进行分析——这在研究同位素标记的生物分子或先进材料时经常用到，或者在对生物样品进行高通量筛选或“芯片实验室”研究时是首选。通过使用静态微线圈、替代检测方案和预极化方法，NMR的灵敏度已得到提高。但这些策略在涉及快速样品旋转（这对于从非液体样品获得分辨率良好的光谱至关重要）的NMR实验中不易使用。在此，我们证明感应耦合允许在探测器线圈和样品都快速旋转的情况下无线传输射频脉冲并接收NMR信号。这使得NMR测量具有最佳填充因子特征，射频场振幅非常高且灵敏度增强，灵敏度随着样品体积减小而增加。与标准NMR测量相比，对于纳升大小的有机粉末和生物组织样品获得的信号增加了近一个数量级（或者等效地，采集速度快了两个数量级）。我们的方法在研究需要限制在多个安全屏障内的样品（如放射性材料）时也提供了最佳灵敏度。原则上，微米级探测器线圈与样品的共同旋转以及感应耦合的使用（我们方法的核心技术）应能对任何需要快速机械旋转以获得分辨率良好光谱的质量受限样品进行高灵敏度NMR测量。该方法易于在商业NMR装置上实现，并且随着小型化表现出更好的性能，因此我们预计它将促进新型固态NMR方法的发展，并在高通量化学和生物医学分析中得到广泛应用。
