Institut für Physikalische Chemie, Universität Göttingen, Tammannstr. 6, D-37077 Göttingen, Germany.
Phys Chem Chem Phys. 2011 Aug 21;13(31):14119-30. doi: 10.1039/c1cp20883g. Epub 2011 Jun 28.
Esters of glycine, alanine and valine are investigated by FTIR and Raman spectroscopy in supersonic jets as gas phase model systems for the neutral peptide N-terminus. The NH-stretching vibrations exhibit very large temperature- and substitution-dependent intensity anomalies which are related to weak, bifurcated intramolecular hydrogen bonds to the carbonyl group. Comparison to theory is only satisfactory at low temperature. Spectral NH aggregation shifts are small or even negligible and the associated IR intensity is remarkably low. In the case of valine, chirality recognition effects are nevertheless detected and rationalized. Comparison to quantum-chemical calculations for dimers shows that dispersion interactions are essential. It also rules out cooperative hydrogen bond topologies and points at deficiencies in standard harmonic treatments with the linear dipole approximation.
甘氨酸、丙氨酸和缬氨酸的酯类在超音速射流中作为中性肽 N-末端的气相模型系统，通过傅里叶变换红外光谱和拉曼光谱进行了研究。NH 伸缩振动表现出非常大的温度和取代依赖性的强度异常，这与羰基的弱、分叉的分子内氢键有关。与理论的比较仅在低温下是令人满意的。光谱 NH 聚集位移很小甚至可以忽略不计，并且相关的 IR 强度非常低。在缬氨酸的情况下，尽管如此，仍检测到并合理化了手性识别效应。与二聚体的量子化学计算相比，表明色散相互作用是必不可少的。它还排除了协同氢键拓扑结构，并指出了标准谐波处理中线性偶极近似的缺陷。
