Whereas specially designed dinitroxide biradicals, reconstitution protocols, oriented sample geometries and NMR probes have helped to much increase the DNP enhancement factors of membrane samples they still lag considerably behind those obtained from glasses made of protein solutions. Here we show that not only the MAS rotor material but also the distribution of the membrane samples within the NMR rotor have a pronounced effect on the DNP enhancement. These observations are rationalized with the cooling efficiency and the internal properties of the sample, monitored by their T₁ relaxation, microwave ON versus OFF signal intensities and DNP effect. The data are suggestive that for membranes the speed of cooling has a pronounced effect on the membrane properties and concomitantly the distribution of biradicals within the sample.

尽管专门设计的二硝基氧双自由基，重构方案，定向的样品几何形状和NMR探针有助于大大增加膜样品的DNP增强因子，但它们仍大大落后于由蛋白质溶液制成的玻璃杯。在这里，我们表明，不仅MAS转子材料而且NMR转子内的膜样品分布对DNP增强都有显着影响。通过观察其T ₁的冷却效率和样品的内部特性，可以合理地观察这些观察结果松弛，微波开启与关闭信号强度以及DNP效应。数据表明，对于膜而言，冷却速度对膜性能以及样品中双自由基的分布有显着影响。