Kumar Santosh, Rai Amareshwar K, Singh V B, Rai S B
Laser and Spectroscopy Laboratory, Department of Physics, BHU, Varanasi 221 005, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2005 Sep;61(11-12):2741-6. doi: 10.1016/j.saa.2004.09.029. Epub 2004 Dec 9.
The infrared and Raman spectra of glycine molecule has been studied in spectral region 400-4000 cm(-1) in solid form as well as in water. The vibrational frequencies for the fundamental modes of the glycine in neutral and its zwitterionic form have also been calculated using AM1 semiempirical method as well as ab initio method with minimal basis set. The reliability of the minimal basis set and AM1 method with higher basis sets, for IR spectra of the neutral glycine conformers were examined. We find that the 6-21G basis set calculation yields structural parameters, rotational constant and dipole moment of glycine conformers, which are very similar to those obtained from extended basis set calculation as well as experimental values. IR frequencies for glycine conformer I are also calculated in water using SCRF=PCM model and compared with experimental values. A comparison between calculated frequencies for neutral glycine, and its zwitterionic form with observed IR and Raman bands have been made. The total energies for gas phase glycine and its zwitterionic form along with those of hydrated forms were also calculated. It is found from the calculations that in the gas phase neutral glycine is more stable as compared to its zwitterionic form.
已经对固态以及水中甘氨酸分子在400 - 4000 cm⁻¹光谱区域的红外和拉曼光谱进行了研究。还使用AM1半经验方法以及具有最小基组的从头算方法计算了中性甘氨酸及其两性离子形式的基本振动模式的振动频率。检验了最小基组和具有更高基组的AM1方法对中性甘氨酸构象异构体红外光谱的可靠性。我们发现，6 - 21G基组计算得出的甘氨酸构象异构体的结构参数、转动常数和偶极矩，与从扩展基组计算以及实验值获得的结果非常相似。还使用SCRF = PCM模型在水中计算了甘氨酸构象异构体I的红外频率，并与实验值进行了比较。对中性甘氨酸及其两性离子形式的计算频率与观察到的红外和拉曼谱带进行了比较。还计算了气相甘氨酸及其两性离子形式以及水合形式的总能量。从计算中发现，在气相中，中性甘氨酸与其两性离子形式相比更稳定。
