物理化学学报 >> 2005, Vol. 21 >> Issue (08): 867-872.doi: 10.3866/PKU.WHXB20050809

研究论文 上一篇    下一篇

用AFM研究DL-缬氨酸晶体的结构及其表面分子的排列

龚; 王文清; 刘虹雯; 杜世萱; 郭海明; 王业亮; 高鸿钧   

  1. 北京大学化学与分子工程学院应用化学系, 北京 100871; 中国科学院物理研究所, 纳米物理和器件实验室, 北京 100080
  • 收稿日期:2004-12-29 修回日期:2005-02-17 发布日期:2005-08-15
  • 通讯作者: 王文清 E-mail:wangwqchem@pku.edu.cn

Surface Recognition of the Space Group and Chiral Array on DL-valine Crystalline Structure Observed by AFM

GONG Yan; WANG Wen-qing; LIU Hong-wen; DU Shi-xuan; GUO Hai-ming; WANG Ye-liang; GAO Hong-jun   

  1. Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871; Nanoscale Physics and Devices Laboratory, Institute of Physics, Chinese Academy of Sciences, Beijing 100080
  • Received:2004-12-29 Revised:2005-02-17 Published:2005-08-15
  • Contact: WANG Wen-qing E-mail:wangwqchem@pku.edu.cn

摘要: 利用原子力显微镜(AFM)成像技术来观察DL-缬氨酸晶体表面分子的规则排列, 研究表明对映体分子在DL-缬氨酸晶体中相互配对排列, 每个晶胞单元中包含两个对映体分子, 属于具有中心对称结构 群, 整个晶体是消旋的. 通过原子力显微镜对DL-缬氨酸晶体表面重复单元的测量结果与X衍射数据对比, 发现用AFM观察到的DL-缬氨酸晶体中分子表面形貌的规整排列的距离, 同X衍射得出的三斜晶系晶胞参数数据基本一致, 由此判定该晶体属于三斜晶系而不是单斜晶系. 探讨了利用纳米技术的研究手段在分子水平研究生命起源中的手性问题, 在确定的晶面上通过分子周期性结构排列规律, 对DL-缬氨酸晶体表面分子进行手性识别.

关键词: 单晶表面手性识别, 空间群, DL-缬氨酸, 原子力显微镜, X射线衍射

Abstract: Atomic force microscopy (AFM) has been used to image arrays of molecules at the surface of DL-valine crystals. AFM images of DL-valine show that D- and L- molecular pairs formed from a DL-racemic mixture are exclusively homochiral. There are two different conclusions about the crystal structure of DL-valine with the data of X-ray crystallography. First, the structure of DL-valine was solved in the monoclinic space group P21/c. Second, the crystal structure of DL-valine has been refined in the centrosymmetric space group and indicated a triclinic rather than a monoclinic space group. The present work emphasizes to solve the contradicting observations of space group and to provide direct evidence for chiral recognition at molecular level. DL-valine molecules {001} are all in zwitterionic form with the isopropyl groups close to the surface and methyl groups on the top site, showing an ordered molecular morphology of triclinic unit cells, which are in fair agreement with the X-ray diffraction data. The application of AFM to the investigation of protein′s origins and a molecular-level illustration of chiral recognition at a periodic 2D surface structure of racemic crystals is discussed.

Key words: Single crystal surface chiral recognition, Space group, DL-valine, AFM, X-ray diffraction