Intense chiral signal from α-helical poly-L-alanine observed in low-frequency Raman optical activity
Intense chiral signal from α-helical poly-L-alanine observed in low-frequency Raman optical activity
复制标题
在低频拉曼光学活性中观察到来自 α-螺旋聚-L-丙氨酸的强手性信号
DOI：
10.1039/d1cp04401j
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发表时间：
2021
影响因子：
3.3
通讯作者：
Bour Petr
中科院分区：
文献类型：
--
作者：
Yamamoto Shigeki;Ishiro Shota;Kessler Jiri;Bour Petr
拉曼光学活性（罗阿）光谱特征可靠地指示肽和蛋白质的结构，但信号通常很弱。然而，我们观察到显着增强的低频带的α-螺旋聚-L-丙氨酸（PLA）在溶液中。在100 cm-1处的最大罗阿信号比先前描述的更高频带强约10倍，这有利于检测。将PLA的低频带与α-螺旋蛋白的低频带进行了比较。对于PLA，密度泛函模拟很好地再现了实验光谱，并揭示了α-螺旋的两个转角内的约12个丙氨酸残基产生强的罗阿带。平均分子动力学（MD）的基础上提供了一个更现实的光谱相比，静态模型。低频带可能在很大程度上与α-螺旋骨架的集体运动有关，部分由溶剂调制。螺旋和分子间振动坐标已经被引入，螺旋解旋模式被分配给101-128 cm-1处最强的罗阿信号。进一步的分析表明，螺旋排列的酰胺基和甲基基团对PLA的强手性信号有重要作用，而局部手性中心CαH的贡献很小.强低频罗阿因此可以提供宝贵的信息，肽骨架的运动和促进未来的蛋白质研究。
Raman optical activity (ROA) spectral features reliably indicate the structure of peptides and proteins, but the signal is often weak. However, we observed significantly enhanced low-frequency bands for α-helical poly-L-alanine (PLA) in solution. The biggest ROA signal at ∼100 cm−1 is about 10 times stronger than higher-frequency bands described previously, which facilitates the detection. The low-frequency bands of PLA were compared to those of α-helical proteins. For PLA, density functional simulations well reproduced the experimental spectra and revealed that about 12 alanine residues within two turns of the α-helix generate the strong ROA band. Averaging based on molecular dynamics (MD) provided an even more realistic spectrum compared to the static model. The low-frequency bands could be largely related to a collective motion of the α-helical backbone, partially modulated by the solvent. Helical and intermolecular vibrational coordinates have been introduced and the helical unwinding modes were assigned to the strongest ROA signal at 101–128 cm−1. Further analysis indicated that the helically arranged amide and methyl groups are important for the strong chiral signal of PLA, while the local chiral centers CαH contribute in a minor way only. The strong low-frequency ROA can thus provide precious information about the motions of the peptide backbone and facilitate future protein studies.