Exploration of Chromophores for VCD Couplet in Biomolecularly Transparent Infrared Region
Exploration of Chromophores for VCD Couplet in Biomolecularly Transparent Infrared Region
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生物分子透明红外区 VCD 对生色团的探索
DOI：
10.1039/d1cp04074j
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Kenji Monde
中科院分区：
文献类型：
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作者：
Tohru Taniguchi;Mohamad Zarif Mohd Zubir;Nobuyuki Harada;Kenji Monde
两个发色团（例如羰基）的相互作用产生反映分子结构的强 VCD 对。由于生物大分子中原本存在的众多官能团导致严重的信号重叠，VCD对用于生物大分子结构研究的使用受到阻碍。腈、异腈、炔和叠氮基团在 2300–2000 cm−1 区域显示出特征红外吸收，而生物分子在该区域吸收不强。我们在此检查了这些官能团作为发色团的有用性，以观察可以使用理论计算轻松解释的强 VCD 对。对具有两个相同发色团的手性联萘支架的研究表明，腈基和异腈基团由于非和谐贡献而产生中等强度但复杂的 VCD 信号。通过与单色发色分子的 VCD 谱比较和非简谐 DFT 计算，讨论了它们的非简谐 VCD 图案的性质。另一方面，通过对二叠氮联萘和二叠氮单糖的研究，我们证明叠氮基由于其简单、强的VCD对，其光谱模式很容易通过谐波DFT计算预测，因此在较大分子的结构分析中更有前景。
Interactions of two chromophores such as carbonyl groups yield a strong VCD couplet that reflects the molecular structures. The use of VCD couplets for biomacromolecular structural studies has been hampered by severe signal overlap caused by numerous functional groups that originally exist in biomacromolecules. Nitrile, isonitrile, alkyne, and azido groups show characteristic IR absorption in the 2300–2000 cm−1 region, where biomolecules do not strongly absorb. We herein examined the usefulness of these functional groups as chromophores to observe a strong VCD couplet that can be readily interpreted using theoretical calculations. Studies on a chiral binaphthyl scaffold possessing two identical chromophores showed that nitrile and isonitrile groups generate moderately-strong but complex VCD signals due to anharmonic contributions. The nature of their anharmonic VCD patterns is discussed by comparison with the VCD spectrum of a mono-chromophoric molecule and by anharmonic DFT calculations. On the other hand, through studies on diazido binaphthyl and diazido monosaccharide, we demonstrated that the azido group is more promising for structural analysis of larger molecules due to its simple, strong VCD couplet whose spectral patterns are readily predicted by harmonic DFT calculations.