Key Laboratory of Mesoscopic Chemistry (Ministry of Education), School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, People's Republic of China.
J Phys Chem B. 2011 Nov 17;115(45):13191-8. doi: 10.1021/jp207863x. Epub 2011 Oct 27.
Recognition and detection of melamine are of very significance in food industries. Molecular recognitions of barbituric acid lipids to melamine at the air-water interface have been investigated in detail using in situ infrared reflection absorption spectroscopy (IRRAS). Hydrogen bonding patterns and molecular orientations of the molecular recognitions have been revealed. Prior to molecular recognition, the barbituric acid moieties in the monolayers were hydrogen bonded with a flat-on fashion at the air-water interface, and the alkyl chains were preferentially oriented with their CCC planes perpendicular to the water surface. After molecular recognition, the NH(2) stretching bands of recognized melamine were clearly observed at the air-water interface as well as primary characteristic bands, the barbituric acid moieties underwent a change in orientation with non-hydrogen bonded C4═O bonds almost perpendicular to the water surface and C2═O and C6═O bonds involved in hydrogen bonds with melamine, and the alkyl chains were preferentially oriented with their CCC planes parallel to the water surface. The monolayers of barbituric acid lipids exhibited excellent selectivity for melamine over nucleosides.
在食品工业中，对三聚氰胺的识别和检测非常重要。本文采用原位红外反射吸收光谱（IRRAS）技术，详细研究了巴比妥酸脂类在气-液界面上对三聚氰胺的分子识别。揭示了分子识别过程中的氢键模式和分子取向。在分子识别之前，单层中的巴比妥酸部分以平卧方式在气-液界面上形成氢键，烷基链优先以其 CCC 平面垂直于水面的方式取向。分子识别后，在气-液界面上清晰地观察到被识别的三聚氰胺的 NH（2）伸缩带以及主要特征带，巴比妥酸部分的取向发生变化，非氢键的 C4═O 键几乎垂直于水面，C2═O 和 C6═O 键与三聚氰胺形成氢键，烷基链优先以其 CCC 平面平行于水面的方式取向。巴比妥酸脂单层对三聚氰胺表现出优于核苷的优异选择性。
