Laage Ségolène, Sachleben Joseph R, Steuernagel Stefan, Pierattelli Roberta, Pintacuda Guido, Emsley Lyndon
Université de Lyon, CNRS/ENS Lyon/UCB-Lyon 1, Centre RMN à Très Hauts Champs, 5 rue de la Doua, 69100 Villeurbanne, France.
J Magn Reson. 2009 Feb;196(2):133-41. doi: 10.1016/j.jmr.2008.10.019. Epub 2008 Nov 7.
The advantages offered by ultra-fast (>60 kHz) magic angle spinning (MAS) rotation for the study of biological samples, notably containing paramagnetic centers are explored. It is shown that optimal conditions for performing solid-state (13)C NMR under 60 kHz MAS are obtained with low-power CW (1)H decoupling, as well as after a low-power (1)H,(13)C cross-polarization step at a double-quantum matching condition. Acquisition with low-power decoupling highlights the existence of rotational decoupling sidebands. The sideband intensities and the existence of first and second rotary conditions are explained in the framework of the Floquet-van Vleck theory. As a result, optimal (13)C spectra of the oxidized, paramagnetic form of human copper zinc superoxide dismutase (SOD) can be obtained employing rf-fields which do not exceed 40 kHz during the whole experiment. This enables the removal of unwanted heating which can lead to deterioration of the sample. Furthermore, combined with the short (1)H T(1)s, this allows the repetition rate of the experiments to be shortened from 3 s to 500 ms, thus compensating for the sensitivity loss due to the smaller sample volume in a 1.3 mm rotor. The result is that 2D (13)C-(13)C correlation could be acquired in about 24 h on less than 1 mg of SOD sample.
探索了超快速(>60 kHz)魔角旋转(MAS)技术在研究生物样品(尤其是含有顺磁中心的样品)方面的优势。结果表明,在60 kHz MAS条件下进行固态(13)C NMR的最佳条件是采用低功率连续波(1)H去耦,以及在双量子匹配条件下进行低功率(1)H - (13)C交叉极化步骤之后。采用低功率去耦采集突出了旋转去耦边带的存在。边带强度以及第一和第二旋转条件的存在在弗洛凯 - 范弗莱克理论框架内得到了解释。结果,在整个实验过程中使用不超过40 kHz的射频场,可以获得人铜锌超氧化物歧化酶(SOD)氧化顺磁形式的最佳(13)C谱。这能够消除可能导致样品变质的不必要加热。此外,结合短的(1)H T(1)s,这使得实验的重复率从3 s缩短到500 ms,从而弥补了由于1.3 mm转子中样品体积较小而导致的灵敏度损失。结果是,在不到1 mg的SOD样品上,大约24小时内可以获得二维(1)3C - (13)C相关谱。