Structural study of α-amino-acid crystals by 1H CRAMPS NMR spectroscopy
Structural study of α-amino-acid crystals by 1H CRAMPS NMR spectroscopy
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DOI：
10.1016/s0022-2860(98)00329-9
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发表时间：
1998-06-22
影响因子：
3.8
通讯作者：
Shoji, A
中科院分区：
文献类型：
--
作者：
Kimura, H;Nakamura, K;Shoji, A
将H-1CRAMPS（组合旋转和多脉冲光谱）NMR应用于α-氨基酸晶体的多晶型形式的结构分析，以测试H-1CRAMPS NMR与C-13和N-15 NMR方法相比的能力。我们研究了α-氨基酸晶体的两个不同阶段：α-甘氨酸和γ-甘氨酸，以及A-组氨酸和B-组氨酸。结果，发现α-甘氨酸的α-亚甲基质子（H-α）信号分裂成两个峰（4.4和3.4ppm），但γ-甘氨酸的信号给出单峰（3.3ppm），这通过该甘氨酸体系的H-1静电势电荷计算合理地解释。此外，发现A-组氨酸的咪唑环的H-2和H-5峰之间的H-1化学位移差（0.4 ppm）可以容易地与B-组氨酸的H-1化学位移差（0.9 ppm）区分开。因此，α-氨基酸的H-1化学位移对质子的磁性环境的微小差异以及氢键网络的差异非常敏感。因此，H-1CRAMPS NMR谱对于α-氨基酸晶体的结构分析是非常有用的。(C)1998 Elsevier Science B. V.保留所有权利。
H-1 CRAMPS (combined rotation and multiple pulse spectroscopy) NMR was applied to structural analysis of polymorphic forms of alpha-amino acid crystals in order to test the power of H-1 CRAMPS NMR compared with the C-13 and N-15 NMR methods. We have studied two different stages of alpha-amino acid crystals: alpha-glycine and gamma-glycine, and A-histidine and B-histidine. As a result, it was found that the alpha-methylene proton (H-alpha) signal of alpha-glycine splits into two peaks (4.4 and 3.4 ppm), but that of gamma- glycine gives a singlet peak (3.3 ppm), which was reasonably explained by the H-1 electrostatic potential charge calculation for this glycine system. Furthermore, it was found that the H-1 chemical shift difference between the H-2 and H-5 peaks from the imidazole ring of A-histidine (0.4 ppm) could easily be distinguished from that of B-histidine (0.9 ppm). Thus, the H-1 chemical shifts of alpha-amino acids are very sensitive to a slight difference in magnetic surroundings of protons as well as to differences of the hydrogen bond network. Therefore, the H-1 CRAMPS NMR spectra are very useful for the structural analysis of alpha-amino acid crystals. (C) 1998 Elsevier Science B.V. All rights reserved.