Chiral discrimination between tyrosine and β-cyclodextrin revealed by cryogenic ion trap infrared spectroscopy
Chiral discrimination between tyrosine and β-cyclodextrin revealed by cryogenic ion trap infrared spectroscopy
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DOI：
10.1039/d0cp02968h
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发表时间：
2020-11-21
影响因子：
3.3
通讯作者：
Zehnacker, Anne
中科院分区：
文献类型：
--
作者：
Hirata, Keisuke;Mori, Yuta;Zehnacker, Anne
通过低温离子阱红外光解离光谱研究了全甲基化β - 环糊精（β - MCD）与质子化酪氨酸的两种对映体（L - 和D - TyrH⁺）形成的复合物。基于密度泛函理论计算，对OH/NH伸缩振动区域和指纹区域的振动光谱进行了指认。L - 和D - TyrH⁺复合物的光谱都包含一种第一种结构的特征，即氨基酸的铵基和酸基同时与β - MCD相互作用，酚羟基保持游离。仅在D - TyrH⁺复合物中观察到第二种结构，涉及酚羟基与β - MCD之间的额外相互作用。质谱中D - TyrH⁺复合物含量较高，初步解释为：（1）D - TyrH⁺更好地插入空腔内，疏水性芳香部分较少暴露于亲水性溶剂分子；（2）一种刚性结构涉及三个相互作用点，即铵基、酚羟基和羧酸羟基，这对于L - TyrH⁺复合物是不可能的。识别过程不是通过诱导与主体分子互补的尺寸效应，而是通过特定的相互作用发生。这些结果全面地理解了环糊精如何识别手性生物分子。
Complexes of permethylated beta-cyclodextrin (beta-MCD) with the two enantiomers of protonated tyrosine (L- and D-TyrH(+)) are studied by cryogenic ion trap infrared photo-dissociation spectroscopy. The vibrational spectra in the OH/NH stretch and fingerprint regions are assigned based on density functional theory calculations. The spectrum of both L- and D-TyrH(+) complexes contains features characteristic of a first structure with ammonium and acid groups of the amino acid simultaneously interacting with the beta-MCD, the phenolic OH remaining free. A second structure involving additional interaction between the phenolic OH and the beta-MCD is observed only for the complex with D-TyrH(+). The larger abundance of the D-TyrH(+) complex in the mass spectrum is tentatively explained in terms of (1) better insertion of D-TyrH(+) within the cavity with the hydrophobic aromatic moiety less exposed to hydrophilic solvent molecules and (2) a stiff structure involving three interaction points, namely the ammonium, the phenolic OH and the carboxylic acid OH, which is not possible for the complex with L-TyrH(+). The recognition process does not occur through size effects that induce complementarity to the host molecule but specific interactions. These results provide a comprehensive understanding of how the cyclodextrin recognises a chiral biomolecule.