An investigation of the hydrogen-bonding structure in bilirubin by 1H double-quantum magic-angle spinning solid-state NMR spectroscopy
An investigation of the hydrogen-bonding structure in bilirubin by 1H double-quantum magic-angle spinning solid-state NMR spectroscopy
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DOI：
10.1021/ja004231h
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发表时间：
2001-05-09
影响因子：
15
通讯作者：
Spiess, HW
中科院分区：
文献类型：
--
作者：
Brown, SP;Zhu, XX;Spiess, HW
复杂的氢键安排在生物学上重要的分子胆红素IX α探测通过使用H-1双量子（BQ）魔角旋转（MAS）NMR光谱。采用快速MAS（30 kHz）和高磁场（16.4 T），三个law-field共振对应于不同的氢键质子的解决在H-1 MAS NMR谱的胆红素。这些共振的基础上分配的质子-质子的接近度从一个二维转子同步的H-1 DQ R;IAS NMR谱。胆红素中NK质子的1H DQ MAS自旋边带图案的分析允许定量测定质子-质子距离和几何形状。对一个三自旋系统的模拟谱证明了该方法的有效性，表明该方法可以很高的精度确定最短距离。胆红素中内酰胺和吡咯NH质子之间的距离测定为0.186 +/- 0.002 nm（对应于18.5 +/- 0.5 kHz的主导偶极耦合常数）。分析还产生内酰胺NH和羧酸OH质子之间的距离为0.230 +/-0.008nm（对应于9.9 +/-1.0kHz的扰动偶极耦合常数）和122 +/-4度的H-H-H角。最后，比较的H-1 DQ MAS自旋边带模式胆红素和其二甲酯揭示了一个显着较长的距离之间的两个NH质子在后者的情况下。
The complex hydrogen-bonding arrangement in the biologically important molecule bilirubin IX alpha is probed by using H-1 double-quantum (BQ) magic-angle spinning (MAS) NMR spectroscopy. Employing fast MAS (30 kHz) and a high magnetic field (16.4 T), three law-field resonances corresponding to the different hydrogen-bonding protons are resolved in a H-1 MAS NMR spectrum of bilirubin. These resonances are assigned on the basis of the proton-proton proximities identified from a two-dimensional rotor-synchronized H-1 DQ R;IAS NMR spectrum. An analysis of 1H DQ MAS spinning-sideband patterns for the NK protons in bilirubin allows the quantitative determination of proton-proton distances and the geometry. The validity of this procedure is proven by simulated spectra for a model three-spin system, which show that the shortest distance can be determined to a very high degree of accuracy. The distance between the lactam and pyrrole NH protons in bilirubin is determined to be 0.186 +/- 0.002 nm (corresponding to a dominant dipolar coupling constant of 18.5 +/- 0.5 kHz). The analysis also yields a distance between the lactam NH and carboxylic acid OH protons of 0.230 +/- 0.008 nm (corresponding to a perturbing dipolar coupling constant of 9.9 +/- 1.0 kHz) and an H-H-H angle of 122 +/- 4 degrees. Finally, a comparison of H-1 DQ MAS spinning-sideband patterns for bilirubin and its dimethyl ester reveals a significantly longer distance between the two NH protons in the latter case.