An infrared study of solid glycine in environments of astrophysical relevance
An infrared study of solid glycine in environments of astrophysical relevance
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DOI：
10.1039/c1cp20899c
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发表时间：
2011-01-01
影响因子：
3.3
通讯作者：
Escribano, Rafael
中科院分区：
文献类型：
--
作者：
Mate, Belen;Rodriguez-Lazcano, Yamilet;Escribano, Rafael
从中性到两性离子甘氨酸的转换研究使用红外光谱从该分子与极性（水）和非极性（CO2，CH 4）环境的相互作用的角度。这样的环境可以在天文或天体物理物质上找到。通过在冷衬底（25 K）上气相沉积来制备样品，然后加热至共沉积物种的升华温度。在25 K，中性物种是有利于在非极性环境中的两性离子形式，而对于纯甘氨酸，或在甘氨酸/水的混合物，占主导地位的物种是后者。转换后很容易减弱中红外区域的两个红外波段，与中性结构相关。理论计算进行结晶甘氨酸和分子甘氨酸，都孤立和包围水。从这些计算预测的光谱与实验光谱是在合理的协议，并提供了一个基础的归属。不同的光谱特征被建议作为探测器存在的甘氨酸在天体物理介质中，这取决于它的形式（中性或两性离子），它们的温度和组成。
The conversion from neutral to zwitterionic glycine is studied using infrared spectroscopy from the point of view of the interactions of this molecule with polar (water) and non-polar (CO2, CH4) surroundings. Such environments could be found on astronomical or astrophysical matter. The samples are prepared by vapour-deposition on a cold substrate (25 K), and then heated up to sublimation temperatures of the co-deposited species. At 25 K, the neutral species is favoured over the zwitterionic form in non-polar environments, whereas for pure glycine, or in glycine/water mixtures, the dominant species is the latter. The conversion is easily followed by the weakening of two infrared bands in the mid-IR region, associated to the neutral structure. Theoretical calculations are performed on crystalline glycine and on molecular glycine, both isolated and surrounded by water. Spectra predicted from these calculations are in reasonable agreement with the experimental spectra, and provide a basis to the assignments. Different spectral features are suggested as probes for the presence of glycine in astrophysical media, depending on its form (neutral or zwitterionic), their temperature and composition.